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  • richardmitnick 10:30 am on January 13, 2022 Permalink | Reply
    Tags: "New theory finds upcoming satellite mission will be able to detect more than expected", A large amount of gravitational waves can be sourced by the quantum vacuum fluctuations of additional fields during inflation., A success story of this hypothesis is that even the simplest inflationary models are able to accurately predict the inhomogeneous distribution of matter in the Universe., Cosmic Inflation, , Detecting these gravitational waves is considered determining the energy at which inflation took place., , How much the inflation field-or the energy source of inflation-can change during inflation — a relation referred to as the “Lyth bound”., JAXA LiteBIRD, Scientists elegantly decoupled the generation of the two types of fluctuations and solved this problem., , These gravitational wave propagating ripples of space and time are important for understanding the physics during the inflationary epoch., Understanding primordial gravitational waves theoretically is gaining interest so any potential detection by LiteBIRD can be interpreted., When you generate gravitational waves from enhanced fluctuations of additional fields you simultaneously generate extra curvature fluctuations.   

    From The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP): “New theory finds upcoming satellite mission will be able to detect more than expected” 

    KavliFoundation

    From The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP)

    Kavli IPMU

    The upcoming satellite experiment LiteBIRD is expected to probe the physics of the very early Universe if the primordial inflation happened at high energies.

    JAXA LiteBIRD Kavli IPMU

    But now, a new paper in Physical Review Letters shows it can also test inflationary scenarios operating at lower energies.

    1
    The green line is the lowest signal the LiteBIRD can still observe, so any observable signal should be above that line. The red and black lines are the team’s predictions for two different parameter specifications in their model, showing detection is possible. In contrast, the more standard inflationary models operating at the same energy as the team’s mechanism predict the lower gray (dashed) line, which is below the sensitivity limit of LiteBIRD. (Credit: Cai et al.)

    Cosmologists believe that in its very early stages, the Universe underwent a very rapid expansion called “cosmic inflation”.

    _____________________________________________________________________________________
    Inflation

    4
    Alan Guth, from M.I.T., who first proposed cosmic inflation.

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

    Alan Guth’s notes:
    Alan Guth’s original notes on inflation.
    _____________________________________________________________________________________

    A success story of this hypothesis is that even the simplest inflationary models are able to accurately predict the inhomogeneous distribution of matter in the Universe. During inflation, these vacuum fluctuations were stretched to astronomical scales, becoming the source all the structure in the Universe, including the Cosmic Microwave Background [CMB] anisotropies, distribution of Dark Matter and galaxies.

    CMB per European Space Agency(EU) Planck.

    The same mechanism also produced gravitational waves.

    Gravitational waves. Credit: W.Benger-Zib. MPG Institute for Gravitational Physics (DE)

    These gravitational wave propagating ripples of space and time are important for understanding the physics during the inflationary epoch. In general, detecting these gravitational waves is considered determining the energy at which inflation took place. It is also linked to how much the inflation field-or the energy source of inflation-can change during inflation — a relation referred to as the “Lyth bound”.

    2
    An artist’s conception of how gravitational waves distort the shape of space and time in the universe (Credit: Kavli IPMU).

    The primordial gravitational waves generated from vacuum are extremely weak, and are very difficult to detect, but the JAXA-led LiteBIRD mission might be able to detect them via the polarization measurements of the Cosmic Microwave Background. Because of this, understanding primordial gravitational waves theoretically is gaining interest so any potential detection by LiteBIRD can be interpreted. It is expected LiteBIRD will be able to detect primordial gravitational waves if inflation happened at sufficiently high energies.

    Several inflationary models constructed in the framework of quantum gravity often predict very low energy scale for inflation, and so would be untestable by LiteBIRD. However, a new study by researchers, including the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), has shown the opposite. The researchers argue such scenarios of fundamental importance can be tested by LiteBIRD, if they are accompanied by additional fields, sourcing gravitational waves.

    The researchers suggest an idea, logically very different from the usual.

    “Within our framework in addition to the gravitational waves originating from vacuum fluctuations, a large amount of gravitational waves can be sourced by the quantum vacuum fluctuations of additional fields during inflation. Due to this we were able to produce an observable amount of gravitational waves even if inflation takes place at lower energies.

    “The quantum fluctuations of scalar fields during inflation are typically small, and such induced gravitational waves are not relevant in standard inflationary scenarios. However, if the fluctuations of the additional fields are enhanced, they can source a significant amount of gravitational waves,” said paper author and Kavli IPMU Project Researcher Valeri Vardanyan.

    Other researchers have been working on related ideas, but so far no successful mechanism based on scalar fields alone had been found.

    “The main problem is that when you generate gravitational waves from enhanced fluctuations of additional fields, you also simultaneously generate extra curvature fluctuations, which would make the Universe appear more clumpy than it is in reality. We elegantly decoupled the generation of the two types of fluctuations and solved this problem,” said Vardanyan.

    In their paper, the researchers proposed a proof-of-concept based on two scalar fields operating during inflation.

    “Imagine a car with two engines, corresponding to the two fields of our model. One of the engines is connected to the wheels of the car, while the other one is not. The first one is responsible for moving the car, and, when on a muddy road, for generating all the traces on the road. These represent the seeds of structure in the Universe. The second engine is only producing sound. This represents the gravitational waves, and does not contribute to the movement of the car, or the generation of traces on the road,” said Vardanyan.

    The team quantitatively demonstrated their mechanism works, and even calculated the predictions of their model for the upcoming LiteBIRD mission.

    See the full article here .

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    The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP) is an international research institute with English as its official language. The goal of the institute is to discover the fundamental laws of nature and to understand the Universe from the synergistic perspectives of mathematics, astronomy, and theoretical and experimental physics. The Institute for the Physics and Mathematics of the Universe (IPMU) was established in October 2007 under the World Premier International Research Center Initiative (WPI) of the Ministry of Education, Sports, Science and Technology in Japan with the University of Tokyo as the host institution. IPMU was designated as the first research institute within the University of Tokyo Institutes for Advanced Study (UTIAS) in January 2011. It received an endowment from The Kavli Foundation and was renamed the “Kavli Institute for the Physics and Mathematics of the Universe” in April 2012. Kavli IPMU is located on the Kashiwa campus of the University of Tokyo, and more than half of its full-time scientific members come from outside Japan. http://www.ipmu.jp/

    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

     
  • richardmitnick 10:30 am on December 14, 2019 Permalink | Reply
    Tags: , , Cosmic Inflation, , , Thermalization, Time’s arrow is irreversible   

    From Quanta Magazine: “The Universal Law That Aims Time’s Arrow” 

    Quanta Magazine
    From Quanta Magazine

    August 1, 2019 [Just now in social media]
    Natalie Wolchover

    1
    Coffee and the cosmos at large both approach thermal equilibrium. Rolando Barry for Quanta Magazine

    Pour milk in coffee, and the eddies and tendrils of white soon fade to brown. In half an hour, the drink cools to room temperature. Left for days, the liquid evaporates. After centuries, the cup will disintegrate, and billions of years later, the entire planet, sun and solar system will disperse. Throughout the universe, all matter and energy is diffusing out of hot spots like coffee and stars, ultimately destined (after trillions of years) to spread uniformly through space. In other words, the same future awaits coffee and the cosmos.

    This gradual spreading of matter and energy, called “thermalization,” aims the arrow of time. But the fact that time’s arrow is irreversible, so that hot coffee cools down but never spontaneously heats up, isn’t written into the underlying laws that govern the motion of the molecules in the coffee. Rather, thermalization is a statistical outcome: The coffee’s heat is far more likely to spread into the air than the cold air molecules are to concentrate energy into the coffee, just as shuffling a new deck of cards randomizes the cards’ order, and repeat shuffles will practically never re-sort them by suit and rank. Once coffee, cup and air reach thermal equilibrium, no more energy flows between them, and no further change occurs. Thus thermal equilibrium on a cosmic scale is dubbed the “heat death of the universe.”

    But while it’s easy to see where thermalization leads (to tepid coffee and eventual heat death), it’s less obvious how the process begins. “If you start far from equilibrium, like in the early universe, how does the arrow of time emerge, starting from first principles?” said Jürgen Berges, a theoretical physicist at Heidelberg University in Germany who has studied this problem for more than a decade.

    Over the last few years, Berges and a network of colleagues have uncovered a surprising answer. The researchers have discovered simple, so-called “universal” laws [World Scientific] governing the initial stages of change in a variety of systems consisting of many particles that are far from thermal equilibrium. Their calculations indicate that these systems — examples include the hottest plasma ever produced on Earth and the coldest gas, and perhaps also the field of energy that theoretically filled the universe in its first split second — begin to evolve in time in a way described by the same handful of universal numbers, no matter what of what the systems consist.

    The findings suggest that the initial stages of thermalization play out in a way that’s very different from what comes later. In particular, far-from-equilibrium systems exhibit fractal-like behavior, which means they look very much the same at different spatial and temporal scales. Their properties are shifted only by a so-called “scaling exponent” — and scientists are discovering that these exponents are often simple numbers like 1-2 and −1/3. For example, particles’ speeds at one instant can be rescaled, according to the scaling exponent, to give the distribution of speeds at any time later or earlier. All kinds of quantum systems in various extreme starting conditions seem to fall into this fractal-like pattern, exhibiting universal scaling for a period of time before transitioning to standard thermalization.

    “I find this work exciting because it pulls out a unifying principle that we can use to understand large classes of far-from-equilibrium systems,” said Nicole Yunger Halpern, a quantum physicist at Harvard University who is not involved in the work. “These studies offer hope that we can describe even these very messy, complicated systems with simple patterns.”

    Berges is widely seen as leading the theoretical effort, with a series of seminal papers since 2008 elucidating the physics of universal scaling. He and a co-author took another step this spring in a paper in Physical Review Letters that explored “prescaling,” the ramp-up to universal scaling. A group led by Thomas Gasenzer of Heidelberg also investigated prescaling in a [Physical Review Letters] paper in May, offering a deeper look at the onset of the fractal-like behavior.

    Some researchers are now exploring far-from-equilibrium dynamics in the lab, as others dig into the origins of the universal numbers. Experts say universal scaling is also helping to address deep conceptual questions about how quantum systems are able to thermalize at all.

    There’s “chaotic progress on various fronts,” said Zoran Hadzibabic of the University of Cambridge. He and his team are studying universal scaling in a hot gas of potassium-39 atoms by suddenly dialing up the atoms’ interaction strength, then letting them evolve.

    Energy Cascades

    When Berges began studying far-from-equilibrium dynamics, he wanted to understand the extreme conditions at the beginning of the universe when the particles that now populate the cosmos originated.

    These conditions would have occurred right after “cosmic inflation” — the explosive expansion of space thought by many cosmologists to have jump-started the Big Bang. Inflation would have blasted away any existing particles, leaving only the uniform energy of space itself: a perfectly smooth, dense, oscillating field of energy known as a “condensate.” Berges modeled this condensate in 2008 [Physical Review Letters] with collaborators Alexander Rothkopf and Jonas Schmidt, and they discovered that the first stages of its evolution should have exhibited fractal-like universal scaling. “You find that when this big condensate decayed into the particles that we observe today, that this process can be very elegantly described by a few numbers,” he said.

    To understand what this universal scaling phenomenon looks like, consider a vivid historical precursor of the recent discoveries. In 1941, the Russian mathematician Andrey Kolmogorov described the way energy “cascades” through turbulent fluids. When you’re stirring coffee, for instance, you create a vortex on a large spatial scale. Kolmogorov realized that this vortex will spontaneously generate smaller eddies, which spawn still smaller eddies. As you stir the coffee, the energy you inject into the system cascades down the spatial scales into smaller and smaller eddies, with the rate of the transfer of energy described by a universal exponential decay factor of −5/3, which Kolmogorov deduced from the fluid’s dimensions.

    Kolmogorov’s “−5/3 law” always seemed mysterious, even as it served as a cornerstone of turbulence research. But now physicists have been finding essentially the same cascading, fractal-like universal scaling phenomenon in far-from-equilibrium dynamics. According to Berges, energy cascades probably arise in both contexts because they are the most efficient way to distribute energy across scales. We instinctively know this. “If you want to distribute your sugar in your coffee, you stir it,” Berges said — as opposed to shaking it. “You know that’s the most efficient way to redistribute energy.”

    There’s one key difference between the universal scaling phenomenon in far-from-equilibrium systems and the fractal eddies in a turbulent fluid: In the fluid case, Kolmogorov’s law describes energy cascading across spatial dimensions. In the new work, researchers see far-from-equilibrium systems undergoing fractal-like universal scaling across both time and space.

    Take the birth of the universe. After cosmic inflation, the hypothetical oscillating, space-filling condensate would have quickly transformed into a dense field of quantum particles all moving with the same characteristic speed. Berges and his colleagues conjecture that these far-from-equilibrium particles then exhibited fractal scaling governed by universal scaling exponents as they began the thermal evolution of the universe.

    3
    Lucy Reading-Ikkanda/Quanta Magazine

    According to the team’s calculations and computer simulations, instead of a single cascade like the one you’d find in a turbulent fluid, there would have been two cascades, going in opposite directions. Most of the particles in the system would have slowed from one moment to the next, cascading to slower and slower speeds at a characteristic rate — in this case, with a scaling exponent of approximately −3/2. Eventually they would have reached a standstill, forming another condensate [Physical Review Letters]. (This one wouldn’t oscillate or transform into particles; instead it would gradually decay.) Meanwhile, the majority of the energy leaving the slowing particles would have cascaded to a few particles that gained speed at a rate governed by the exponent 1/2. Essentially, these particles started to move extremely fast.

    The fast particles would have subsequently decayed into the quarks, electrons and other elementary particles that exist today. These particles would then have undergone standard thermalization, scattering off each other and distributing their energy. That process is still ongoing in the present-day universe and will continue for trillions of years.

    Simplicity Occurs

    The ideas about the early universe aren’t easily testable. But around 2012, the researchers realized that a far-from-equilibrium scenario also arises in experiments — namely, when heavy atomic nuclei are smashed together at nearly the speed of light in the Relativistic Heavy Ion Collider in New York and in Europe’s Large Hadron Collider.


    BNL RHIC

    CERN LHC

    These nuclear collisions create extreme configurations of matter and energy, which then start to relax toward equilibrium. You might think the collisions would produce a complicated mess. But when Berges and his colleagues analyzed the collisions theoretically, they found structure and simplicity. The dynamics, Berges said, “can be encoded in a few numbers.”

    The pattern continued. Around 2015, after talking to experimentalists who were probing ultracold atomic gases in the lab, Berges, Gasenzer and other theorists calculated that these systems should also exhibit universal scaling after being rapidly cooled to conditions extremely far from equilibrium.

    Last fall, two groups — one led by Markus Oberthaler of Heidelberg and the other by Jörg Schmiedmayer of the Vienna Center for Quantum Science and Technology — reported simultaneously in Nature [np link that they had observed fractal-like universal scaling in the way various properties of the 100,000-or-so atoms in their gases changed over space and time. “Again, simplicity occurs,” said Berges, who was one of the first to predict the phenomenon in such systems. “You can see that the dynamics can be described by a few scaling exponents and universal scaling functions. And some of them turned out to be the same as what was predicted for particles in the early universe. That’s the universality.”

    The researchers now believe that the universal scaling phenomenon occurs at the nanokelvin scale of ultracold atoms, the 10-trillion-kelvin scale of nuclear collisions, and the 10,000-trillion-trillion-kelvin scale of the early universe. “That’s the point of universality — that you can expect to see these phenomena on different energy and length scales,” Berges said.

    The case of the early universe may hold the most intrinsic interest, but it’s the highly controlled, isolated laboratory systems that are enabling scientists to tease out the universal rules governing the beginning stages of change. “We know everything that’s in the box,” as Hadzibabic put it. “It’s this isolation from the environment that allows you to study the phenomenon in its pure form.”

    One major thrust has been to figure out where systems’ scaling exponents come from. In some cases, experts have traced the exponents [Physical Review D] to the number of spatial dimensions a system occupies, as well as its symmetries — that is, all the ways it can be transformed without changing (just as a square stays the same when rotated by 90 degrees).

    Those insights are helping to address a paradox about what happens to information about the past as systems thermalize. Quantum mechanics requires that as particles evolve, information about their past is never lost. And yet, thermalization seems to contradict this: When two neglected cups of coffee are both at room temperature, how can you tell which one started out hotter?

    It seems that as a system begins to evolve, key details, like its symmetries, are retained and become encoded in the scaling exponents dictating its fractal evolution, while other details, like the initial configuration of its particles or the interactions between them, become irrelevant to its behavior, scrambled among its particles.

    And this scrambling process happens very early indeed. In their papers this spring, Berges, Gasenzer and their collaborators independently described prescaling for the first time, a period before universal scaling that their papers predicted for nuclear collisions and ultracold atoms, respectively. Prescaling suggests that when a system first evolves from its initial, far-from-equilibrium condition, scaling exponents don’t yet perfectly describe it. The system retains some of its previous structure — remnants of its initial configuration. But as prescaling progresses, the system assumes a more universal form in space and time, essentially obscuring irrelevant information about its own past. If this idea is borne out by future experiments, prescaling may be the nocking of time’s arrow onto the bowstring.

    See the full article here .


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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 8:58 am on April 22, 2019 Permalink | Reply
    Tags: "Before the Big Bang", , , , Cosmic Inflation, , , , Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey   

    From Harvard Gazette: “Before the Big Bang” 


    Harvard University


    From Harvard Gazette

    April 18, 2019
    Peter Reuell

    Study outlines new proposal for probing the primordial universe.

    1
    NASA WMAP

    Most everybody is familiar with the Big Bang — the notion that an impossibly hot, dense universe exploded into the one we know today. But what do we know about what came before?

    In the quest to resolve several puzzles discovered in the initial condition of the Big Bang, scientists have developed a number of theories to describe the primordial universe, the most successful of which — known as cosmic inflation — describes how the universe dramatically expanded in size in a fleeting fraction of a second right before the Big Bang.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    But as successful as the inflationary theory has been, controversies have led to active debates over the years.

    Some researchers have developed very different theories to explain the same experimental results that have supported the inflationary theory so far. In some of these theories, the primordial universe was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.

    Some researchers — including Avi Loeb, the Frank B. Baird, Jr. Professor of Science and chair of the Astronomy Department — have raised concerns about the theory, suggesting that its seemingly endless adaptability makes it all but impossible to test.

    “The current situation for inflation is that it’s such a flexible idea … it cannot be falsified experimentally,” Loeb said. “No matter what result of the observable people set out to measure would turn out to be, there are always some models of inflation that can explain it.” Therefore, experiments can only help to nail down some model details within the framework of the inflationary theory, but cannot test the validity of the framework itself. However, falsifiability should be a hallmark of any scientific theory.

    That’s where Xingang Chen comes in.

    1
    Xingang Chen is one of the authors of a new study that examines what the universe looked like before the Big Bang. Jon Chase/Harvard Staff Photographer.

    A senior lecturer in astronomy, Chen and his collaborators for many years have been developing the idea of using something he called a “primordial standard clock” as a probe of the primordial universe. Together with Loeb and Zhong-Zhi Xianyu, a postdoctoral researcher in the Physics Department, Chen applied this idea to the noninflationary theories after he learned about an intense debate in 2017 that questioned whether inflationary theories make any predictions at all. In a paper published as an Editor’s Suggestion in Physical Review Letters, the team laid out a method that may be used to falsify the inflationary theory experimentally.

    In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories — the evolutionary history of the size of the primordial universe. “For example, during inflation, by definition the size of the universe grows exponentially,” Xianyu said. “In some alternative theories, the size of the universe contracts — in some very slowly and in some very fast.

    “The conventional observables people have proposed so far have trouble distinguishing the different theories because these observables are not directly related to this property,” he continued. “So we wanted to find what the observables are that can be linked to that defining property.”

    The signals generated by the primordial standard clock can serve this purpose.

    That clock, Chen said, is any type of massively heavy elementary particle in the energetic primordial universe. Such particles should exist in any theory, and they oscillate at some regular frequency, much like the swaying of a clock’s pendulum.

    The primordial universe was not entirely uniform. Quantum fluctuations became the seeds of the large-scale structure of today’s universe and one key source of information physicists rely on to learn about what happened before the Big Bang. The theory outlined by Chen suggests that ticks of the standard clock generated signals that were imprinted into the structure of those fluctuations. And because standard clocks in different primordial universes would leave different patterns of signals, Chen said, they may be able to determine which theory of the primordial universe is most accurate.

    “If we imagine all the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played,” Chen explained. “Without any clock information, we do not know if the film should be played forward or backward, fast or slow — just like we are not sure if the primordial universe was inflating or contracting, and how fast it did that. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us what this film is about.”

    The team calculated how these standard clock signals should look in noninflationary theories, and suggested how to search for them in astrophysical observations. “If a pattern of signals representing a contracting universe were found,” Xianyu said, “it would falsify the entire inflationary theory, regardless of what detailed models one constructs.”

    The success of this idea lies in experimentation. “These signals will be very subtle to detect,” Chen said. “Our proposal is that there should be some kind of massive fields that have generated these imprints and we computed their patterns, but we don’t know how large the overall amplitude of these signals is. It may be that they are very faint and very hard to detect, so that means we will have to search in many different places.

    “The cosmic microwave background [CMB] radiation is one place,” he continued. “The distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already, but we still need more data.”

    Cosmic Background Radiation per Planck

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    See the full article here .

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    Harvard University campus
    Harvard University is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

     
  • richardmitnick 11:31 am on January 8, 2019 Permalink | Reply
    Tags: , Antiuniverse, , Cosmic Inflation, CPT symmetry, , Our universe has antimatter partner on the other side of the Big Bang say physicists, , , , The entity that respects the symmetry is a universe–antiuniverse pair   

    From physicsworld.com: “Our universe has antimatter partner on the other side of the Big Bang, say physicists” 

    physicsworld
    From physicsworld.com

    03 Jan 2019

    1
    (Courtesy: shutterstock/tomertu)

    Our universe could be the mirror image of an antimatter universe extending backwards in time before the Big Bang. So claim physicists in Canada, who have devised a new cosmological model positing the existence of an “antiuniverse” [Physical Review Letters] which, paired to our own, preserves a fundamental rule of physics called CPT symmetry. The researchers still need to work out many details of their theory, but they say it naturally explains the existence of dark matter.

    Standard cosmological models tell us that the universe – space, time and mass/energy – exploded into existence some 14 billion years ago and has since expanded and cooled, leading to the progressive formation of subatomic particles, atoms, stars and planets.

    However, Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario reckons that these models’ reliance on ad-hoc parameters means they increasingly resemble Ptolemy’s description of the solar system. One such parameter, he says, is the brief period of rapid expansion known as inflation that can account for the universe’s large-scale uniformity. “There is this frame of mind that you explain a new phenomenon by inventing a new particle or field,” he says. “I think that may turn out to be misguided.”

    Instead, Turok and his Perimeter Institute colleague Latham Boyle set out to develop a model of the universe that can explain all observable phenomena based only on the known particles and fields. They asked themselves whether there is a natural way to extend the universe beyond the Big Bang – a singularity where general relativity breaks down – and then out the other side. “We found that there was,” he says.

    The answer was to assume that the universe as a whole obeys CPT symmetry. This fundamental principle requires that any physical process remains the same if time is reversed, space inverted and particles replaced by antiparticles. Turok says that this is not the case for the universe that we see around us, where time runs forward as space expands, and there’s more matter than antimatter.

    2
    In a CPT-symmetric universe, time would run backwards from the Big Bang and antimatter would dominate (L Boyle/Perimeter Institute of Theoretical Physics)

    Instead, says Turok, the entity that respects the symmetry is a universe–antiuniverse pair. The antiuniverse would stretch back in time from the Big Bang, getting bigger as it does so, and would be dominated by antimatter as well as having its spatial properties inverted compared to those in our universe – a situation analogous to the creation of electron–positron pairs in a vacuum, says Turok.

    Turok, who also collaborated with Kieran Finn of Manchester University in the UK, acknowledges that the model still needs plenty of work and is likely to have many detractors. Indeed, he says that he and his colleagues “had a protracted discussion” with the referees reviewing the paper for Physical Review Letters [link is above] – where it was eventually published – over the temperature fluctuations in the cosmic microwave background. “They said you have to explain the fluctuations and we said that is a work in progress. Eventually they gave in,” he says.

    In very broad terms, Turok says, the fluctuations are due to the quantum-mechanical nature of space–time near the Big Bang singularity. While the far future of our universe and the distant past of the antiuniverse would provide fixed (classical) points, all possible quantum-based permutations would exist in the middle. He and his colleagues counted the instances of each possible configuration of the CPT pair, and from that worked out which is most likely to exist. “It turns out that the most likely universe is one that looks similar to ours,” he says.

    Turok adds that quantum uncertainty means that universe and antiuniverse are not exact mirror images of one another – which sidesteps thorny problems such as free will.

    But problems aside, Turok says that the new model provides a natural candidate for dark matter. This candidate is an ultra-elusive, very massive particle called a “sterile” neutrino hypothesized to account for the finite (very small) mass of more common left-handed neutrinos. According to Turok, CPT symmetry can be used to work out the abundance of right-handed neutrinos in our universe from first principles. By factoring in the observed density of dark matter, he says that quantity yields a mass for the right-handed neutrino of about 5×108 GeV – some 500 million times the mass of the proton.

    Turok describes that mass as “tantalizingly” similar to the one derived from a couple of anomalous radio signals spotted by the Antarctic Impulsive Transient Antenna (ANITA). The balloon-borne experiment, which flies high over Antarctica, generally observes cosmic rays travelling down through the atmosphere. However, on two occasions ANITA appears to have detected particles travelling up through the Earth with masses between 2 and 10×108 GeV. Given that ordinary neutrinos would almost certainly interact before getting that far, Thomas Weiler of Vanderbilt University and colleagues recently proposed that the culprits were instead decaying right-handed neutrinos [Letters in High Energy Physics].

    Turok, however, points out a fly in the ointment – which is that the CPT symmetric model requires these neutrinos to be completely stable. But he remains cautiously optimistic. “It is possible to make these particles decay over the age of the universe but that takes a little adjustment of our model,” he says. “So we are still intrigued but I certainly wouldn’t say we are convinced at this stage.”

    See the full article here .


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    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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  • richardmitnick 10:32 pm on September 10, 2018 Permalink | Reply
    Tags: , , Cosmic Inflation, , ,   

    From Stanford University: “The String Theory Landscape” 

    Stanford University Name
    From Stanford University

    September 10, 2018
    Ker Than

    1
    The String Theory Landscape combines elements of string theory and cosmic inflation to greatly expand the scope of the Big Bang theory to incorporate the idea of infinite universes in a vast multiverse. (Image credit: Eric Nyquist)

    The most recent update to the Big Bang theory, called the String Theory Landscape, arose out of elements of string theory and cosmic inflation.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    The theory’s inclusion of a multiverse and its denial of immutable physical laws has raised debates that continue to this day. This story is part 1 of a five-part series.

    The Big Bang theory describes the abrupt origins of space and time from a swiftly unfurling singularity – a hot, dense point of pure potential, packed impossibly full with eternity and the rudiments of creation. As with the universe it seeks to explain, the theory is endlessly evolving. Ever since its proposal nearly a century ago, physicists have revised and remade it to reflect new scientific concepts and discoveries.

    The latest draft of the scientific story of genesis is called the String Theory Landscape. Entwined at its heart are two of the strangest and most enduring ideas in modern physics – string theory and cosmic inflation – which Stanford physicists helped bring together nearly two decades ago.

    String theory asserts that the basic building blocks of reality are vibrating, one-dimensional loops of energy that quiver in 10 or more dimensions to strum out the elementary particles and fundamental forces of nature.

    Cosmic inflation holds that the Big Bang began with a period of exponential expansion that swelled our universe from a fragile quantum speck to a vast manor of emptiness a quarter-billion-light-years wide in a flicker of a flicker of time.

    According to the theory, this heavenly sprawl still occurs in distant corners of the cosmos, spinning out a web of related daughter universes that connect to form a much larger “multiverse.”

    For decades, the two theories circled one another, each advancing along a seemingly unique track and independently gaining momentum among physicists, until an unexpected discovery drove them together. The String Theory Landscape was born in the wake of their collision – and physics has never been quite the same since.

    It was an “earthquake that caused enormous consternation and controversy among theoretical physicists,” wrote Leonard Susskind, the Felix Bloch Professor in Physics at Stanford’s School of Humanities and Sciences, in his 2005 book The Cosmic Landscape.

    ____________________________________________________

    “It probably bothered the first human beings who realized that the world was not just their local valley. It probably terrified them a little bit, but by now we’re used to the world getting bigger and bigger. The String Theory Landscape just says it’s way bigger than we thought.”

    —Leonard Susskind

    Professor of Physics

    ____________________________________________________

    An old debate

    The String Theory Landscape rekindled the ashes of an old debate in physics, one that smolders to this day. On one side are those who contend, as Albert Einstein once did, that the laws of nature are elegant, immutable and inevitable, and that they can be discovered and described through mathematics. In contrast, most Landscape proponents believe that while the underlying equations of string theory may be simple and elegant, the solutions to those equations are tremendously complex and infinitely diverse.

    This diversity, they say, is key to explaining certain baffling features of our universe, like the fact that several parameters in physics and cosmology appear to be curiously fine-tuned for life forms like us to exist. Perhaps the most glaring example is the cosmological constant, which relates to a universal repulsive force that is pushing space-time apart. Physicists have struggled to explain why the tiny value of this constant just happens to lie within the narrow band that allows stars and planets to form and biological life to evolve. But if there are innumerable universes, each with differing laws of physics, then it should not be surprising that we inhabit one where the cosmological constant is small – if things were any different, we could not exist to marvel at the coincidence.

    “The String Theory Landscape potentially explains many properties of our world,” said physicist Andrei Linde, the Harald Trap Friis Professor at Stanford. “It may explain not just the cosmological constant, but also why the mass of the proton and neutron are almost exactly the same, why the electron mass is so small, and why we live in a universe with three dimensions of space and not 10. There is no other theory that can do that.”

    The String Theory Landscape also rouses fierce emotions because it touches upon questions that cut to the heart of modern physics and science in general. If gravity’s strength can vary from one universe to the next, what is the point of trying to understand its extraordinary weakness in our universe? And if a theory can’t make testable predictions, is it still science? “One dominant view in the community is that believing in the Landscape might have the negative effect of leading people away from fundamental physics, so we shouldn’t even discuss it,” said Shamit Kachru, who holds the Wells Family Directorship of the Stanford Institute for Theoretical Physics (SITP).

    Landscape supporters say the theory is just the latest helping of humble pie that humanity has had to swallow as its sense of privilege in the universe has been slowly effaced by centuries of scientific progress. “It probably bothered the first human beings who realized that the world was not just their local valley,” Susskind said. “It probably terrified them a little bit, but by now we’re used to the world getting bigger and bigger. The String Theory Landscape just says it’s way bigger than we thought.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 2:42 pm on July 28, 2018 Permalink | Reply
    Tags: , , , , Cosmic Inflation, , , , Hubble Constant not so constant   

    From European Space Agency: “From an almost perfect Universe to the best of both worlds” 

    ESA Space For Europe Banner

    From European Space Agency

    Jan Tauber
    ESA Planck Project Scientist
    European Space Agency
    Email: jan.tauber@esa.int

    Markus Bauer
    ESA Science Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    17 July 2018

    The Planck consortium has made their final data release, including new processing of the cosmic microwave background temperature and polarisation data. This legacy dataset confirms the model of an ‘almost perfect Universe’, with some remaining oddities giving researchers some intriguing details to puzzle over.

    1
    The Cosmic Microwave Background – as seen by Planck. Credit: ESA and the Planck Collaboration

    ESA/Planck 2009 to 2013

    It was 21 March 2013. The world’s scientific press had either gathered in ESA’s Paris headquarters or logged in online, along with a multitude of scientists around the globe, to witness the moment when ESA’s Planck mission revealed its ‘image’ of the cosmos. This image was taken not with visible light but with microwaves.

    Whereas light that our eyes can see is composed of small wavelengths – less than a thousandth of a millimetre in length – the radiation that Planck was detecting spanned longer wavelengths, from a few tenths of a millimetre to a few millimetres. Most importantly, it had been generated at very beginning of the Universe.

    Collectively, this radiation is known as the cosmic microwave background, or CMB. By measuring its tiny differences across the sky, Planck’s image had the ability to tell us about the age, expansion, history, and contents of the Universe. It was nothing less than the cosmic blueprint.

    Astronomers knew what they were hoping to see. Two NASA missions, COBE in the early 1990s and WMAP in the following decade, had already performed an analogous set of sky surveys that resulted in similar images. But those images did not have the precision and sharpness of Planck.

    The new view would show the imprint of the early Universe in painstaking detail for the first time. And everything was riding on it.

    If our model of the Universe were correct, then Planck would confirm it to unprecedented levels of accuracy. If our model were wrong, Planck would send scientists back to the drawing board.

    When the image was revealed, the data had confirmed the model. The fit to our expectations was too good to draw any other conclusion: Planck had showed us an ‘almost perfect Universe’. Why almost perfect? Because a few anomalies remained, and these would be the focus of future research.

    Now, five years later, the Planck consortium has made their final data release, known as the legacy data release. The message remains the same, and is even stronger.

    2
    Planck’s view of the sky in nine channels at microwave and sub-millimetre wavelenghts.
    Credit: ESA and the Planck Collaboration, animated

    “This is the most important legacy of Planck,” says Jan Tauber, ESA’s Planck Project Scientist. “So far the standard model of cosmology has survived all the tests, and Planck has made the measurements that show it.”

    Standard Model of Cosmology Timeline

    Standard Model of Cosmology Cornell

    All cosmological models are based upon Albert Einstein’s General Theory of Relativity. To reconcile the general relativistic equations with a wide range of observations, including the cosmic microwave background, the standard model of cosmology includes the action of two unknown components.

    Firstly, an attractive matter component, known as cold dark matter, which unlike ordinary matter does not interact with light. Secondly, a repulsive form of energy, known as dark energy, which is driving the currently accelerated expansion of the Universe. They have been found to be essential components to explain our cosmos in addition to the ordinary matter we know about. But as yet we do not know what these exotic components actually are.

    Planck was launched in 2009 and collected data until 2013. Its first release – which gave rise to the almost perfect Universe – was made in the spring of that year. It was based solely on the temperature of the cosmic microwave background radiation, and used only the first two sky surveys from the mission.

    The data also provided further evidence for a very early phase of accelerated expansion, called inflation, in the first tiny fraction of a second in the Universe’s history, during which the seeds of all cosmic structures were sown. Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    Yielding a quantitative measure of the relative distribution of these primordial fluctuations, Planck provided the best confirmation ever obtained of the inflationary scenario.

    Besides mapping the temperature of the cosmic microwave background across the sky with unprecedented accuracy, Planck also measured its polarisation, which indicates if light is vibrating in a preferred direction. The polarisation of the cosmic microwave background carries an imprint of the last interaction between the radiation and matter particles in the early Universe, and as such contains additional, all-important information about the history of the cosmos. But it could also contain information about the very first instants of our Universe, and give us clues to understand its birth.

    In 2015, a second data release folded together all data collected by the mission, which amounted to eight sky surveys. It gave temperature and polarisation but came with a caution.

    “We felt the quality of some of the polarisation data was not good enough to be used for cosmology,” says Jan. He adds that – of course – it didn’t prevent them from doing cosmology with it but that some conclusions drawn at that time needed further confirmation and should therefore be treated with caution.

    And that’s the big change for this 2018 Legacy data release. The Planck consortium has completed a new processing of the data. Most of the early signs that called for caution have disappeared. The scientists are now certain that both temperature and polarisation are accurately determined.

    “Now we really are confident that we can retrieve a cosmological model based on solely on temperature, solely on polarisation, and based on both temperature and polarisation. And they all match,” says Reno Mandolesi, principal investigator of the LFI instrument on Planck at the University of Ferrara, Italy.

    “Since 2015, more astrophysical data has been gathered by other experiments, and new cosmological analyses have also been performed, combining observations of the CMB at small scales with those of galaxies, clusters of galaxies, and supernovae, which most of the time improved the consistency with Planck data and the cosmological model supported by Planck,” says Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.

    This is an impressive feat and means that cosmologists can be assured that their description of the Universe as a place containing ordinary matter, cold dark matter and dark energy, populated by structures that had been seeded during an early phase of inflationary expansion, is largely correct.

    But there are some oddities that need explaining – or tensions as cosmologists call them. One in particular is related to the expansion of the Universe. The rate of this expansion is given by the so-called Hubble Constant.

    To measure the Hubble constant astronomers have traditionally relied on gauging distances across the cosmos. They can only do this for the relatively local Universe by measuring the apparent brightness of certain types of nearby variable stars and exploding stars, whose actual brightness can be estimated independently. It is a well-honed technique that has been developed over the course of the last century, pioneered by Henrietta Leavitt and later applied, in the late 1920s, by Edwin Hubble and collaborators, who used variable stars in distant galaxies and other observations to reveal that the Universe was expanding.

    The figure astronomers derive for the Hubble Constant using a wide variety of cutting-edge observations, including some from Hubble’s namesake observatory, the NASA/ESA Hubble Space Telescope, and most recently from ESA’s Gaia mission, is 73.5 km/s/Mpc, with an uncertainty of only two percent. The slightly esoteric units give the velocity of the expansion in km/s for every million parsecs (Mpc) of separation in space, where a parsec is equivalent to 3.26 light-years.

    A second way to estimate the Hubble Constant is to use the cosmological model that fits the cosmic microwave background image, which represents the very young Universe, and calculate a prediction for what the Hubble Constant should be today. When applied to Planck data, this method gives a lower value of 67.4 km/s/Mpc, with a tiny uncertainty of less than a percent.

    1
    Measurements of the Hubble constant over the past two decades.
    Credit: ESA and the Planck Collaboration

    On the one hand, it is extraordinary that two such radically different ways of deriving the Hubble constant – one using the local, mature Universe, and one based on the distant, infant Universe – are so close to each other. On the other hand, in principle these two figures should agree to within their respective uncertainties. This is the tension, and the question is how can they be reconciled?

    Both sides are convinced that any remaining errors in their measurement methodologies are now too small to cause the discrepancy. So could it be that there is something slightly peculiar about our local cosmic environment that makes the nearby measurement somewhat anomalous? We know for example that our Galaxy sits in a slightly under-dense region of the Universe, which could affect the local value of the Hubble constant. Unfortunately, most astronomers think that such deviations are not large enough to resolve this problem.

    “There is no single, satisfactory astrophysical solution that can explain the discrepancy. So, perhaps there is some new physics to be found,” says Marco Bersanelli, deputy principal investigator of the LFI instrument at the University of Milan, Italy.

    ‘New physics’ means that exotic particles or forces could be influencing the results. Yet, as exciting as this prospect feels, the Planck results place severe constraints on this train of thought because it fits so well with the majority of observations.

    “It is very hard to add new physics alleviating the tension and still keep the standard model’s precise description of everything else that already fits,” says François Bouchet, deputy principal investigator of the HFI instrument at the Institut d’Astrophysique de Paris, France.

    As a result, no one has been able to come up with a satisfactory explanation for the differences between the two measurements, and the question remains to be resolved.

    “For the moment, we shouldn’t get too excited about finding new physics: it could well be that the relatively small discrepancy can be explained by a combination of small errors and local effects. But we need to keep improving our measurements and thinking about better ways to explain it,” says Jan.

    This is the legacy of Planck: with its almost perfect Universe, the mission has given researchers confirmation of their models but with a few details to puzzle over. In other words: the best of both worlds.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 8:47 am on July 18, 2018 Permalink | Reply
    Tags: , , , , Cosmic Inflation, , , ,   

    From European Space Agency: “From an almost perfect Universe to the best of both worlds” 

    ESA Space For Europe Banner

    From European Space Agency

    17 July 2018

    Jan Tauber
    ESA Planck Project Scientist
    European Space Agency
    Email: jan.tauber@esa.int

    Markus Bauer
    ESA Science Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    1
    CMB per Planck

    ESA/Planck 2009 to 2013

    It was 21 March 2013. The world’s scientific press had either gathered in ESA’s Paris headquarters or logged in online, along with a multitude of scientists around the globe, to witness the moment when ESA’s Planck mission revealed its ‘image’ of the cosmos. This image was taken not with visible light but with microwaves.

    Whereas light that our eyes can see is composed of small wavelengths – less than a thousandth of a millimetre in length – the radiation that Planck was detecting spanned longer wavelengths, from a few tenths of a millimetre to a few millimetres. Most importantly, it had been generated at very beginning of the Universe.

    Collectively, this radiation is known as the cosmic microwave background, or CMB. By measuring its tiny differences across the sky, Planck’s image had the ability to tell us about the age, expansion, history, and contents of the Universe. It was nothing less than the cosmic blueprint.

    Astronomers knew what they were hoping to see. Two NASA missions, COBE in the early 1990s and WMAP in the following decade, had already performed an analogous set of sky surveys that resulted in similar images. But those images did not have the precision and sharpness of Planck.

    COBE/CMB

    NASA/COBE 1989 to 1993.

    CMB per NASA/WMAP

    NASA/WMAP 2001 to 2010

    The new view would show the imprint of the early Universe in painstaking detail for the first time. And everything was riding on it.

    If our model of the Universe were correct, then Planck would confirm it to unprecedented levels of accuracy. If our model were wrong, Planck would send scientists back to the drawing board.

    When the image was revealed, the data had confirmed the model. The fit to our expectations was too good to draw any other conclusion: Planck had showed us an ‘almost perfect Universe’. Why almost perfect? Because a few anomalies remained, and these would be the focus of future research.

    Now, five years later, the Planck consortium has made their final data release, known as the legacy data release. The message remains the same, and is even stronger.

    All cosmological models are based upon Albert Einstein’s General Theory of Relativity. To reconcile the general relativistic equations with a wide range of observations, including the cosmic microwave background, the standard model of cosmology includes the action of two unknown components.

    Firstly, an attractive matter component, known as cold dark matter, which unlike ordinary matter does not interact with light. Secondly, a repulsive form of energy, known as dark energy, which is driving the currently accelerated expansion of the Universe. They have been found to be essential components to explain our cosmos in addition to the ordinary matter we know about. But as yet we do not know what these exotic components actually are.

    3
    CMB temperature and polarisation

    Planck was launched in 2009 and collected data until 2013. Its first release – which gave rise to the almost perfect Universe – was made in the spring of that year. It was based solely on the temperature of the cosmic microwave background radiation, and used only the first two sky surveys from the mission.

    The data also provided further evidence for a very early phase of accelerated expansion, called inflation, in the first tiny fraction of a second in the Universe’s history, during which the seeds of all cosmic structures were sown.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    Yielding a quantitative measure of the relative distribution of these primordial fluctuations, Planck provided the best confirmation ever obtained of the inflationary scenario.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    Besides mapping the temperature of the cosmic microwave background across the sky with unprecedented accuracy, Planck also measured its polarisation, which indicates if light is vibrating in a preferred direction. The polarisation of the cosmic microwave background carries an imprint of the last interaction between the radiation and matter particles in the early Universe, and as such contains additional, all-important information about the history of the cosmos. But it could also contain information about the very first instants of our Universe, and give us clues to understand its birth.

    In 2015, a second data release folded together all data collected by the mission, which amounted to eight sky surveys. It gave temperature and polarisation but came with a caution.

    5
    5 February 2015 New maps from ESA’s Planck satellite uncover the ‘polarised’ light from the early Universe across the entire sky, revealing that the first stars formed much later than previously thought.

    “We felt the quality of some of the polarisation data was not good enough to be used for cosmology,” says Jan. He adds that – of course – it didn’t prevent them from doing cosmology with it but that some conclusions drawn at that time needed further confirmation and should therefore be treated with caution.

    And that’s the big change for this 2018 Legacy data release. The Planck consortium has completed a new processing of the data. Most of the early signs that called for caution have disappeared. The scientists are now certain that both temperature and polarisation are accurately determined.

    “Now we really are confident that we can retrieve a cosmological model based on solely on temperature, solely on polarisation, and based on both temperature and polarisation. And they all match,” says Reno Mandolesi, principal investigator of the LFI instrument on Planck at the University of Ferrara, Italy.

    6

    The history of the Universe

    “Since 2015, more astrophysical data has been gathered by other experiments, and new cosmological analyses have also been performed, combining observations of the CMB at small scales with those of galaxies, clusters of galaxies, and supernovae, which most of the time improved the consistency with Planck data and the cosmological model supported by Planck,” says Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.

    This is an impressive feat and means that cosmologists can be assured that their description of the Universe as a place containing ordinary matter, cold dark matter and dark energy, populated by structures that had been seeded during an early phase of inflationary expansion, is largely correct.

    But there are some oddities that need explaining – or tensions as cosmologists call them. One in particular is related to the expansion of the Universe. The rate of this expansion is given by the so-called Hubble Constant.

    To measure the Hubble constant astronomers have traditionally relied on gauging distances across the cosmos. They can only do this for the relatively local Universe by measuring the apparent brightness of certain types of nearby variable stars and exploding stars, whose actual brightness can be estimated independently. It is a well-honed technique that has been developed over the course of the last century, pioneered by Henrietta Leavitt and later applied, in the late 1920s, by Edwin Hubble and collaborators, who used variable stars in distant galaxies and other observations to reveal that the Universe was expanding.

    7
    Measurements of the Hubble constant
    Released 17/07/2018 3:00 pm
    Copyright ESA/Planck Collaboration

    The evolution of measurements of the rate of the Universe’s expansion, given by the so-called Hubble Constant, over the past two decades. The slightly esoteric units give the velocity of the expansion in km/s for every million parsecs (Mpc) of separation in space, where a parsec is equivalent to 3.26 light-years.
    In recent years, the figure astronomers derive for the Hubble Constant using a wide variety of cutting-edge observations to gauge distances across the cosmos is 73.5 km/s/Mpc, with an uncertainty of only two percent. These measurements are shown in blue.
    Alternatively, the Hubble Constant can also be estimated from the cosmological model that fits observations of the cosmic microwave background, which represents the very young Universe, and calculate a prediction for what the Hubble Constant should be today. Measurements based on this method using data from NASA’s WMAP satellite are shown in green, and those obtained using data from ESA’s Planck mission are shown in red.
    When applied to Planck data, this method gives a lower value of 67.4 km/s/Mpc, with a tiny uncertainty of less than a percent.

    On the one hand, it is extraordinary that two such radically different ways of deriving the Hubble constant – one using the local, mature Universe, and one based on the distant, infant Universe – are so close to each other. On the other hand, in principle these two figures should agree to within their respective uncertainties, causing what cosmologists call a ‘tension’ – an oddity that still needs explaining.

    The single purple point is a measurement obtained through yet another method, using data from the first simultaneous observation of light and gravitational waves emitted by the same source – a pair of coalescing neutron stars.

    The figure astronomers derive for the Hubble Constant using a wide variety of cutting-edge observations, including some from Hubble’s namesake observatory, the NASA/ESA Hubble Space Telescope, and most recently from ESA’s Gaia mission, is 73.5 km/s/Mpc, with an uncertainty of only two percent. The slightly esoteric units give the velocity of the expansion in km/s for every million parsecs (Mpc) of separation in space, where a parsec is equivalent to 3.26 light-years.

    NASA/ESA Hubble Telescope

    ESA/GAIA satellite

    A second way to estimate the Hubble Constant is to use the cosmological model that fits the cosmic microwave background image, which represents the very young Universe, and calculate a prediction for what the Hubble Constant should be today. When applied to Planck data, this method gives a lower value of 67.4 km/s/Mpc, with a tiny uncertainty of less than a percent.

    On the one hand, it is extraordinary that two such radically different ways of deriving the Hubble constant – one using the local, mature Universe, and one based on the distant, infant Universe – are so close to each other. On the other hand, in principle these two figures should agree to within their respective uncertainties. This is the tension, and the question is how can they be reconciled?

    Both sides are convinced that any remaining errors in their measurement methodologies are now too small to cause the discrepancy. So could it be that there is something slightly peculiar about our local cosmic environment that makes the nearby measurement somewhat anomalous? We know for example that our Galaxy sits in a slightly under-dense region of the Universe, which could affect the local value of the Hubble constant. Unfortunately, most astronomers think that such deviations are not large enough to resolve this problem.

    “There is no single, satisfactory astrophysical solution that can explain the discrepancy. So, perhaps there is some new physics to be found,” says Marco Bersanelli, deputy principal investigator of the LFI instrument at the University of Milan, Italy.

    ‘New physics’ means that exotic particles or forces could be influencing the results. Yet, as exciting as this prospect feels, the Planck results place severe constraints on this train of thought because it fits so well with the majority of observations.

    “It is very hard to add new physics alleviating the tension and still keep the standard model’s precise description of everything else that already fits,” says François Bouchet, deputy principal investigator of the HFI instrument at the Institut d’Astrophysique de Paris, France.

    As a result, no one has been able to come up with a satisfactory explanation for the differences between the two measurements, and the question remains to be resolved.

    “For the moment, we shouldn’t get too excited about finding new physics: it could well be that the relatively small discrepancy can be explained by a combination of small errors and local effects. But we need to keep improving our measurements and thinking about better ways to explain it,” says Jan.

    This is the legacy of Planck: with its almost perfect Universe, the mission has given researchers confirmation of their models but with a few details to puzzle over. In other words: the best of both worlds.

    Notes for Editors
    A series of scientific papers describing the new results was published on 17 July and can be downloaded here.

    The Planck Legacy Archive
    More about Planck

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 2:17 pm on February 24, 2018 Permalink | Reply
    Tags: , , , , Cosmic Inflation, , , Why Haven't We Bumped Into Another Universe Yet?   

    From Ethan Siegel: “Why Haven’t We Bumped Into Another Universe Yet?” 

    From Ethan Siegel
    Feb 24, 2018

    1
    The multiverse idea states that there are an arbitrarily large number of Universes like our own, but that doesn’t necessarily mean there’s another version of us out there, and it certainly doesn’t mean there’s any chance of running into an alternate version of yourself… or anything from another Universe at all. Lee Davy / flickr.

    The Universe we inhabit is vast, full of matter and energy, and expanding at a tremendous clip. Looking billions of light years away, we can see billions of years into our ancient past, finding evidence of newly-forming planets, stars, and galaxies. We’ve seen so far back that we’ve identified clouds of gas that have never yet formed a single star, and found galaxies from when the Universe was only 3% of its current age. Most spectacularly, we can actually see the leftover glow from the Big Bang, from a time when the Universe was a mere 380,000 years old. Yet in all of this cosmic enormity, we’ve never found evidence that our Universe has bumped into another one in this vast Multiverse. Why not? That’s what Rod Russo wants to know:

    “If the Multiverse Theory is true, shouldn’t our expanding universe have bumped into another universe by now? After all, our universe is now so large that some describe it as “infinite” in size.”

    This is not only what logic dictates, it’s what no less an authority than Roger Penrose has claimed. But Penrose — and conventional wisdom — are both wrong here. Our Universe is, and should be, isolated and alone in the Multiverse.

    2
    Artist’s logarithmic scale conception of the observable universe. Note that we’re limited in how far we can see back by the amount of time that’s occurred since the hot Big Bang: 13.8 billion years, or (including the expansion of the Universe) 46 billion light years. Anyone living in our Universe, at any location, would see almost exactly the same thing from their vantage point. Wikipedia user Pablo Carlos Budassi.

    Although there’s a lot of hype and controversy surrounding it, there’s an extremely strong physical motivation for the existence of the Multiverse. If you combine two of our leading ideas about how the Universe works, cosmic inflation and quantum physics, it’s all but inescapable that we’ll conclude that our Universe resides in a Multiverse. Coming along for the ride is another conclusion: that every single Universe that gets created — that every hot Big Bang that ensues — is immediately and forever causally disconnected from all the others, eternally into the future. Here’s how that happens, and here’s how we know.

    3
    The expanding Universe, full of galaxies and the complex structure we observe today, arose from a smaller, hotter, denser, more uniform state. But what lies outside the observable Universe, by definition, cannot be observed. C. Faucher-Giguère, A. Lidz, and L. Hernquist, Science 319, 5859 (47).

    Cosmic inflation came about as an add-on to the Big Bang, successfully providing a mechanism for explaining why it began with certain conditions.

    4
    Alan Guth, Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:

    In particular, inflation provided answer to the questions of:

    why the Universe was the same temperature everywhere,
    why it was so spatially flat,
    and why there were no leftover high-energy relics like magnetic monopoles,

    while simultaneously making new predictions that could be tested. These predictions included a specific spectrum for the density fluctuations the Universe was born with, a maximum temperature that the Universe achieved in the early stages of the hot Big Bang, the existence of fluctuations on scales larger than the cosmic horizon, and a particular spectrum of gravitational wave fluctuations. All of these, except the very last, have since been observationally confirmed.

    6
    Inflation set up the hot Big Bang and gave rise to the observable Universe we have access to, but we can only measure the last tiny fraction of a second of inflation’s impact on our Universe. This is enough, however, to give us a large slew of predictions to go out an look for, many of which have already been observationally confirmed. E. Siegel, with images derived from ESA/Planck and the DoE/NASA/ NSF interagency task force on CMB research

    What cosmic inflation is, exactly, is a period prior [?*] to the Big Bang where the Universe is dominated by the energy inherent to space itself. Unlike today, where the value of dark energy is extremely small, inflation posits that it was extremely large: larger by far than even the energy density when the Universe was full of matter and radiation in the extremely hot, early stages after the Big Bang. Since the expansion was dominated by the energy inherent to space, the rate of expansion was exponential, meaning that new space was continuously and rapidly created. If the Universe doubled in size after a certain amount of time, then after ten times that amount of time passed, it’d be 210, or over 1000, times as large in all dimensions. In extremely short order, any non-flat, matter-containing region of space would become indistinguishable from flat, and would have all the matter particles inflated away so that no two would ever meet.

    7
    Inflation causes space to expand exponentially, which can very quickly result in any pre-existing curved space appearing flat. E. Siegel (L); Ned Wright’s cosmology tutorial (R).

    On the other hand, inflation must come to an end at some point. The energy inherent to space cannot remain there forever, otherwise the Big Bang never would have occurred [?*], and the Universe as we know it would never have come to be. Somehow, that energy needs to get transferred from the fabric of space itself and dumped into matter and radiation. A nice way to visualize this is to view inflation as a field that occurs when a ball is at the top of a hill. As long as the ball remains up high, inflation, and this exponential expansion, continues. But in order for inflation to end, whatever quantum field is responsible for it has to roll from the high-energy, unstable state that drives inflation down into a low-energy, equilibrium state. That transition, and “rolling” down into the valley, is what causes inflation to come to an end, and create the hot Big Bang.

    8
    When cosmic inflation occurs, the energy inherent in space is large, as it is at the top of this hill. As the ball rolls down into the valley, that energy converts into particles. E. Siegel.

    But here’s the kicker: what I just described is how a classical field works, but we just said that inflation has to be, like all physical fields, an inherently quantum one. Like all quantum fields, it’s described by a wavefunction, with the probability of that wave spreading out over time. If the value of the field is rolling slowly-enough down the hill, then the quantum spreading of the wavefunction will be faster than the roll, meaning that it’s possible — even probable — for inflation to wind up farther away from ending and giving rise to a Big Bang as time goes on.

    9
    If inflation is a quantum field, then the field value spreads out over time, with different regions of space taking different realizations of the field value. In many regions, the field value will wind up in the bottom of the valley, ending inflation, but in many more, inflation will continue, arbitrarily far into the future. E. Siegel / Beyond The Galaxy.

    Because space is expanding at an exponential rate during inflation, this means that exponentially more regions of space are being created as time goes on. The thing is, inflation isn’t compelled to end everywhere at once; different regions will see the value of their quantum fields spread out by different amounts and in different directions over time! In a few regions, inflation will come to an end, as long as the field rolls down into the valley. But in others, inflation will continue on, giving rise to more and more space, where it continues to expand exponentially.

    10
    Wherever inflation occurs (blue cubes), it gives rise to exponentially more regions of space with each step forward in time. Even if there are many cubes where inflation ends (red Xs), there are far more regions where inflation will continue on into the future. The fact that this never comes to an end is what makes inflation ‘eternal’ once it begins. E. Siegel / Beyond The Galaxy.

    This is where the phenomenon known as eternal inflation, and the idea of a multiverse, comes from. Where inflation ends, we get a hot Big Bang and a Universe — of which we can observe part of the one we’re in — very much like our own. (Denoted by the red “X” above.) But surrounding each of those regions where a hot Big Bang occurs is one where inflation doesn’t end, and the exponential expansion continues. In those regions, more inflating space is produced, driving apart the regions where inflation ended at a faster rate than they’re capable of expanding at. This gives rise to other regions that will have hot Big Bangs, but each and every one of them will be causally disconnected from our own, at the moment of the hot Big Bang and forever into the future.

    If you picture the Multiverse as an enormous ocean, you can picture the individual Universes where a hot Big Bang occurs as little bubbles appearing in it. The bubbles, like real air bubbles that rise from the bottom of the ocean, will expand as time goes on, just as our own Universe is expanding. But unlike the liquid water of the ocean, the “ocean” of inflating spacetime keeps on expanding at a faster rate than the bubbles themselves can ever expand. As long as the space between them continues to inflate, and inflation predicts they will for an eternity, no two bubbles should ever collide. Unlike the boiling water on your stove, the bubbles don’t percolate.

    It would be an enormous surprise that runs counter to inflation and quantum theory’s predictions if any two Universes ever did collide. While bubble-wall collisions might leave a telltale sign on our Universe, we’ve examined the leftover glow from the Big Bang in gory detail, and no evidence for such a collision exists. Thankfully for our most robust theories of the early Universe, this is exactly in line with what’s been predicted. The reason we don’t see evidence for our Universe colliding with another is because our Universe has never collided with another one, just as our leading theories predict. Anyone who tells you otherwise has got some serious explaining to do.

    *I question Siegel’s assertion that inflation occurred prior to the Big Bang. I have never seen that and Alan Guth did not see that. From Wikipedia:

    “In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to sometime between 10^−33 and 10^−32 seconds after the singularity. Following the inflationary period, the Universe continues to expand, but at a less rapid rate…As a junior particle physicist, [Alan] Guth developed the idea of cosmic inflation in 1979 at Cornell and gave his first seminar on the subject in January 1980.Moving on to Stanford University Guth formally proposed the idea of cosmic inflation in 1981, the idea that the nascent universe passed through a phase of exponential expansion that was driven by a positive vacuum energy density (negative vacuum pressure). The results of the WMAP mission in 2006 made the case for cosmic inflation very compelling.”

    I mean really, Ethan, how can you post inflation prior to the Big Bang? I have seen no one posit this before.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 1:47 pm on July 19, 2017 Permalink | Reply
    Tags: , , , , Cosmic Inflation, , Scientists Are Using the Universe as a "Cosmological Collider",   

    From CfA: “Scientists Are Using the Universe as a “Cosmological Collider” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 19, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

    1

    Physicists are capitalizing on a direct connection between the largest cosmic structures and the smallest known objects to use the universe as a “cosmological collider” and investigate new physics.

    The three-dimensional map of galaxies throughout the cosmos and the leftover radiation from the Big Bang – called the cosmic microwave background (CMB) – are the largest structures in the universe that astrophysicists observe using telescopes.

    CMB per ESA/Planck

    ESA/Planck

    Subatomic elementary particles, on the other hand, are the smallest known objects in the universe that particle physicists study using particle colliders.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    A team including Xingang Chen of the Harvard-Smithsonian Center for Astrophysics (CfA), Yi Wang from the Hong Kong University of Science and Technology (HKUST) and Zhong-Zhi Xianyu from the Center for Mathematical Sciences and Applications at Harvard University has used these extremes of size to probe fundamental physics in an innovative way. They have shown how the properties of the elementary particles in the Standard Model of particle physics may be inferred by studying the largest cosmic structures. This connection is made through a process called cosmic inflation.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Inflationary Universe. NASA/WMAP

    Cosmic inflation is the most widely accepted theoretical scenario to explain what preceded the Big Bang. This theory predicts that the size of the universe expanded at an extraordinary and accelerating rate in the first fleeting fraction of a second after the universe was created.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    It was a highly energetic event, during which all particles in the universe were created and interacted with each other. This is similar to the environment physicists try to create in ground-based colliders, with the exception that its energy can be 10 billion times larger than any colliders that humans can build.

    Inflation was followed by the Big Bang, where the cosmos continued to expand for more than 13 billion years, but the expansion rate slowed down with time. Microscopic structures created in these energetic events got stretched across the universe, resulting in regions that were slightly denser or less dense than surrounding areas in the otherwise very homogeneous early universe. As the universe evolved, the denser regions attracted more and more matter due to gravity. Eventually, the initial microscopic structures seeded the large-scale structure of our universe, and determined the locations of galaxies throughout the cosmos.

    In ground-based colliders, physicists and engineers build instruments to read the results of the colliding events. The question is then how we should read the results of the cosmological collider.

    “Several years ago, Yi Wang and I, Nima Arkani-Hamed and Juan Maldacena from the Institute of Advanced Study, and several other groups, discovered that the results of this cosmological collider are encoded in the statistics of the initial microscopic structures. As time passes, they become imprinted in the statistics of the spatial distribution of the universe’s contents, such as galaxies and the cosmic microwave background, that we observe today,” said Xingang Chen. “By studying the properties of these statistics we can learn more about the properties of elementary particles.”

    As in ground-based colliders, before scientists explore new physics, it is crucial to understand the behavior of known fundamental particles in this cosmological collider, as described by the Standard Model of particle physics.

    “The relative number of fundamental particles that have different masses – what we call the mass spectrum – in the Standard Model has a special pattern, which can be viewed as the fingerprint of the Standard Model,” explained Zhong-Zhi Xiangyu. “However, this fingerprint changes as the environment changes, and would have looked very different at the time of inflation from how it looks now.”

    The team showed what the mass spectrum of the Standard Model would look like for different inflation models. They also showed how this mass spectrum is imprinted in the appearance of the large-scale structure of our universe. This study paves the way for the future discovery of new physics.

    “The ongoing observations of the CMB and large-scale structure have achieved impressive precision from which valuable information about the initial microscopic structures can be extracted,” said Yi Wang. “In this cosmological collider, any observational signal that deviates from that expected for particles in the Standard Model would then be a sign of new physics.”

    The current research is only a small step towards an exciting era when precision cosmology will show its full power.

    “If we are lucky enough to observe these imprints, we would not only be able to study particle physics and fundamental principles in the early universe, but also better understand cosmic inflation itself. In this regard, there are still a whole universe of mysteries to be explored,” said Xianyu.

    This research is detailed in a paper published in the journal Physical Review Letters on June 29, 2017, and the preprint is available online.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 3:05 pm on June 3, 2017 Permalink | Reply
    Tags: , , , Cosmic Inflation, , What does the edge of the Universe look like?   

    From Ethan Siegel: “What does the edge of the Universe look like?” 

    From Ethan Siegel
    June 3, 2017

    1
    The simulated large-scale structure of the Universe shows intricate patterns of clustering that never repeat. But from our perspective, we can only see a finite volume of the Universe. What lies beyond this edge? Image credit: V. Springel et al., MPA Garching, and the Millenium Simulation.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    “The Edge… there is no honest way to explain it because the only people who really know where it is are the ones who have gone over.”
    -Hunter S. Thompson

    13.8 billion years ago, the Universe as we know it began with the hot Big Bang. Over that time, space itself has expanded, the matter has undergone gravitational attraction, and the result is the Universe we see today. But as vast as it all is, there’s a limit to what we can see. Beyond a certain distance, the galaxies disappear, the stars twinkle out, and no signals from the distant Universe can be seen. What lies beyond that? That’s this week’s question from Dan Newman, who asks:

    If the universe is finite in volume, then is there a boundary? Is it approachable? And what might the view in that direction be?

    Let’s start by starting at our present location, and looking out as far into the distance as we can.

    2
    Nearby, the stars and galaxies we see look very much like our own. But as we look farther away, we see the Universe as it was in the distant past: less structured, hotter, younger, and less evolved. Image credit: NASA, ESA, and A. Feild (STScI).

    NASA/ESA Hubble Telescope

    In our own backyard, the Universe is full of stars. But go more than about 100,000 light years away, and you’ve left the Milky Way behind. Beyond that, there’s a sea of galaxies: perhaps two trillion in total contained in our observable Universe. They come in a great diversity of types, shapes, sizes and masses. But as you look back to the more distant ones, you start to find something unusual: the farther away a galaxy is, the more likely it is to be smaller, lower in mass, and to have its stars be intrinsically bluer in color than the nearby ones.

    3
    How galaxies appear different at different points in the Universe’s history: smaller, bluer, younger, and less evolved at earlier times. Image credit: NASA, ESA, P. van Dokkum (Yale University), S. Patel (Leiden University), and the 3D-HST Team.

    This makes sense in the context of a Universe that had a beginning: a birthday. That’s what the Big Bang was, the day that the Universe as we know it was born. For a galaxy that’s relatively close by, it’s just about the same age that we are. But when we look at a galaxy that’s billions of light years away, that light has needed to travel for billions of years to reach our eyes. A galaxy whose light takes 13 billion years to reach us must be less than one billion years old, and so the farther away we look, we’re basically looking back in time.

    4
    The full UV-visible-IR composite of the Hubble eXtreme Deep Field; the greatest image ever released of the distant Universe. Image credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI).

    The above image is the Hubble eXtreme Deep Field (XDF), the deepest image of the distant Universe ever taken. There are thousands of galaxies in this image, at a huge variety of distances from us and from one another. What you can’t see in simple color, though, is that each galaxy has a spectrum associated with it, where clouds of gas absorb light at very particular wavelengths, based on the simple physics of the atom. As the Universe expands, that wavelength stretches, so the more distant galaxies appear redder than they otherwise would. That physics allows us to infer their distance, and lo and behold, when we assign distances to them, the farthest galaxies are the youngest and smallest ones of all.

    Beyond the galaxies, we expect there to be the first stars, and then nothing but neutral gas, when the Universe hadn’t had enough time to pull matter into dense enough states to form a star yet. Going back additional millions of years, the radiation in the Universe was so hot that neutral atoms couldn’t form, meaning that photons bounced off of charged particles continuously. When neutral atoms did form, that light should simply stream in a straight line forever, unaffected by anything other than the expansion of the Universe. The discovery of this leftover glow — the Cosmic Microwave Background — more than 50 years ago was the ultimate confirmation of the Big Bang.

    Cosmic Microwave Background WMAP

    NASA WMAP

    CMB per ESA/Planck

    ESA/Planck

    4
    Schematic diagram of the Universe’s history, highlighting reionization. Before stars or galaxies formed, the Universe was full of light-blocking, neutral atoms. While most of the Universe doesn’t become reionized until 550 million years afterwards, a few fortunate regions are mostly reionized at earlier times. Image credit: S. G. Djorgovski et al., Caltech Digital Media Center.

    So from where we are today, we can look out in any direction we like and see the same cosmic story unfolding. Today, 13.8 billion years after the Big Bang, we have the stars and galaxies we know today. Earlier, galaxies were smaller, bluer, younger and less evolved. Before that, there were the first stars, and prior to that, just neutral atoms. Before neutral atoms, there was an ionized plasma, then even earlier there were free protons and neutrons, spontaneous creation of matter-and-antimatter, free quarks and gluons, all the unstable particles in the Standard Model, and finally the moment of the Big Bang itself. Looking to greater and greater distances is equivalent to looking all the way back in time.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    5
    Artist’s logarithmic scale conception of the observable universe. Galaxies give way to large-scale structure and the hot, dense plasma of the Big Bang at the outskirts. This ‘edge’ is a boundary only in time. Image credit: Wikipedia user Pablo Carlos Budassi.

    Although this defines our observable Universe — with the theoretical boundary of the Big Bang located 46.1 billion light years from our current position — this is not a real boundary in space. Instead, it’s simply a boundary in time; there’s a limit to what we can see because the speed of light allows information to only travel so far over the 13.8 billion years since the hot Big Bang. That distance is farther than 13.8 billion light years because the fabric of the Universe has expanded (and continues to expand), but it’s still limited. But what about prior to the Big Bang? What would you see if you somehow went to the time just a tiny fraction of a second earlier than when the Universe was at its highest energies, hot and dense, and full of matter, antimatter and radiation?

    6
    Inflation set up the hot Big Bang and gave rise to the observable Universe we have access to. The fluctuations from inflation planted the seeds that grew into the structure we have today. Image credit: Bock et al. (2006, astro-ph/0604101); modifications by E. Siegel.

    You’d find that there was a state called cosmic inflation: where the Universe was expanding ultra fast, and dominated by energy inherent to space itself. Space expanded exponentially during this time, where it was stretched flat, where it was given the same properties everywhere, where pre-existing particles were all pushed away, and where fluctuations in the quantum fields inherent to space were stretched across the Universe. When inflation ended where we are, the hot Big Bang filled the Universe with matter and radiation, giving rise to the part of the Universe — the observable Universe — that we see today. 13.8 billion years later, here we are.

    Inflation theorist Alan Guth:

    4
    Alan Guth, Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    5
    Alan Guth’s notes. http://www.bestchinanews.com/Explore/4730.html

    6
    The observable Universe might be 46 billion light years in all directions from our point of view, but there’s certainly more, unobservable Universe, perhaps even an infinite amount, just like ours beyond that. Image credit: Frédéric MICHEL and Andrew Z. Colvin, annotated by E. Siegel.

    The thing is, there’s nothing special about our location, neither in space nor in time. The fact that we can see 46 billion light years away doesn’t make that boundary or that location anything special; it simply marks the limit of what we can see. If we could somehow take a “snapshot” of the entire Universe, going way beyond the observable part, as it exists 13.8 billion years after the Big Bang everywhere, it would all look like our nearby Universe does today. There would be a great cosmic web of galaxies, clusters, filaments, and cosmic voids, extending far beyond the comparatively small region we can see. Any observer, at any location, would see a Universe that was very much like the one we see from our own perspective.

    7
    One of the most distant views of the Universe showcases nearby stars and galaxies seen along the way, but the galaxies closer to the outer regions are simply seen at a younger, earlier stage of evolution. From their perspective, they are 13.8 billion years old (and more evolved), and we appear as we did billions of years ago. Image credit: NASA, ESA, the GOODS Team and M. Giavalisco (STScI/University of Massachusetts).

    The individual details would be different, just as the details of our own solar system, galaxy, local group, and so on, are different from any other observer’s viewpoint. But the Universe itself isn’t finite in volume; it’s only the observable part that’s finite. The reason for that is that there’s a boundary in time — the Big Bang — that separates us from the rest. We can approach that boundary only through telescopes (which look to earlier times in the Universe) and through theory. Until we figure out how to circumvent the forward flow of time, that will be our only approach to better understand the “edge” of the Universe. But in space? There’s no edge at all. To the best that we can tell, someone at the edge of what we see would simply see us as the edge instead!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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