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  • richardmitnick 9:02 am on September 29, 2021 Permalink | Reply
    Tags: "Creating order by mechanical deformation in dense active matter", , Living systems are active-demonstrating fascinating properties such as adapting to their environment or repairing themselves., , Researchers have now discovered a novel type of ordering effect generated and sustained by a simple mechanical deformation-specifically steady shear., There is a hidden order-force directions: these tend to point towards the nearest (top or bottom) plate while particles with sideways forces aggregate in the middle of the system., University of Göttingen [Georg-August-Universität Göttingen](DE)   

    From University of Göttingen [Georg-August-Universität Göttingen](DE): “Creating order by mechanical deformation in dense active matter” 


    From University of Göttingen [Georg-August-Universität Göttingen](DE)

    24.09.2021

    Contacts:
    Dr Rituparno Mandal
    Institute of Theoretical Physics
    University of Göttingen
    rituparno.mandal@theorie.physik.uni-goettingen.de
    Tel: +49 (0)551 39 26958

    Professor Peter Sollich
    Institute of Theoretical Physics
    University of Göttingen
    peter.sollich@theorie.physik.uni-goettingen.de

    Researchers at Göttingen University use computer simulation to investigate models of living system.

    1
    A snapshot of the researchers’ simulation showing orientational ordering under steady shear deformation. Colours code the orientation of the self-propulsion forces, e.g. blue for downward and red for upward; neighbouring particles tend to be oriented in similar directions. Photo: Dr Rituparno Mandal.

    Living or biological systems cannot be easily understood using the standard laws of physics, such as thermodynamics, as scientists would for gases, liquids or solids. Living systems are active-demonstrating fascinating properties such as adapting to their environment or repairing themselves. Exploring the questions posed by living systems using computer simulations, researchers at the University of Göttingen have now discovered a novel type of ordering effect generated and sustained by a simple mechanical deformation, specifically steady shear. The results were published in PNAS.

    Understanding living systems, such as tissues formed by cells, poses a significant challenge because of their unique properties, such as adaptation, self-repair and self-propulsion. Nonetheless, they can be studied using models that treat them as just an unusual, “active” form of physical matter. This can reveal extraordinary dynamical or mechanical properties. One of the puzzles is how active materials behave under shear (the deformation produced by moving the top and bottom layers sideways in opposite directions, like sliding microscope cover plates against each other). Researchers at the Institute for Theoretical Physics, University of Göttingen explored this question and discovered a novel type of ordering effect that is generated and sustained by steady shear deformation. The researchers used a computer model of self-propelling particles where each particle is driven by a propulsion force that changes direction slowly and randomly. They found that while the flow of the particles looks similar to that in ordinary liquids, there is a hidden order revealed by looking at the force directions: these tend to point towards the nearest (top or bottom) plate, while particles with sideways forces aggregate in the middle of the system.

    “We were exploring the response of a model active material under steady driving, where the system is sandwiched between two walls, one stationary and the other moving to generate shear deformation. What we saw was that at a sufficiently strong driving force, an interesting ordering effect emerges,” comments Dr Rituparno Mandal, Institute for Theoretical Physics at the University of Göttingen. “We now also understand the ordering effect using a simple analytical theory and the predictions from this theory match surprisingly well with the simulation.”

    Senior author Professor Peter Sollich, also from the Institute for Theoretical Physics, University of Göttingen, explains, “Often an external force or driving force destroys ordering. But here the driving by shear flow is key in providing mobility to the particles that make up the active material, and they actually need this mobility to achieve the observed order. The results will open up exciting possibilities for researchers investigating the mechanical responses of living matter.”

    This research was made possible thanks to funding from the European Union’s Horizon 2020 research and innovation programme under a Marie Skłodowska-Curie grant.

    See the full article here.

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    The University of Göttingen [Georg-August-Universität Göttingen] (DE), is a public research university in the city of Göttingen, Germany. Founded in 1734 by George II, King of Great Britain and Elector of Hanover, and starting classes in 1737, the Georgia Augusta was conceived to promote the ideals of the Enlightenment. It is the oldest university in the state of Lower Saxony and the largest in student enrollment, which stands at around 31,600.

    Home to many noted figures, it represents one of Germany’s historic and traditional institutions. As of October 2020, 44 Nobel Prize winners have been affiliated with the University of Göttingen as alumni, faculty members or researchers.

    The University of Göttingen was previously supported by the German Universities Excellence Initiative, holds memberships to the U15 Group of major German research universities and to the Coimbra Group of major European research universities. Furthermore, the university maintains strong connections with major research institutes based in Göttingen, such as those of the Max Planck Society(DE) and the Leibniz Association [Leibniz-Gemeinschaft or Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz](DE). With approximately 9 million media units, the Göttingen State and University Library ranks among the largest libraries in Germany.

    Partner institutions

    Within the Göttingen Campus the university is organizationally and personally interlinked with the following independent and semi-independent institutions:

    Max Planck Institute for Biophysical Chemistry (Karl Friedrich Bonhoeffer Institute)
    Max Planck Institute for Experimental Medicine
    Max Planck Institute for Dynamics and Self-Organization, formerly Max Planck Institute for Flow Research
    Max Planck Institute for the Study of Religious and Ethnic Diversity, formerly Max Planck Institute for History
    Max Planck Institute for Solar System Research, formerly Max Planck Institute for Aeronomy
    German Primate Center – Leibniz Institute for Primate Research
    German Aerospace Center

     
  • richardmitnick 4:57 pm on March 25, 2021 Permalink | Reply
    Tags: "The very first structures in the Universe", , Astrophysicists at the University of Göttingen(DE) and University of Auckland(NZ) simulate microscopic clusters from the Big Bang., , , , University of Auckland(NZ), University of Göttingen [Georg-August-Universität Göttingen](DE)   

    From University of Göttingen [Georg-August-Universität Göttingen](DE) and University of Auckland(NZ): “The very first structures in the Universe” 

    From University of Göttingen [Georg-August-Universität Göttingen](DE)

    and

    2

    From University of Auckland(NZ)

    24.03.2021

    Benedikt Eggemeier
    University of Göttingen(DE)
    Institute for Astrophysics
    benedikt.eggemeier@phys.uni-goettingen.de

    Professor Jens Niemeyer
    University of Göttingen(DE)
    Institute for Astrophysics
    jens.niemeyer@phys.uni-goettingen.de

    Professor Richard Easther
    University of Auckland(NZ)
    Department of Physics
    r.easther@auckland.ac.nz

    1
    The results of the simulation show the growth of tiny, extremely dense structures very soon after the inflation phase of the very early universe. Between the initial and final states in the simulation (top left and right respectively), the area shown has expanded to ten million times its initial volume, but is still many times smaller than the interior of a proton. The enlarged clump at the bottom left would have a mass of about 20kg. Credit: Jens Niemeyer/ University of Göttingen [Georg-August-Universität Göttingen](DE)

    Astrophysicists at the University of Göttingen [Georg-August-Universität Göttingen](DE) and University of Auckland(NZ) simulate microscopic clusters from the Big Bang.

    The very first moments of the Universe can be reconstructed mathematically even though they cannot be observed directly. Physicists from the University of Göttingen [Georg-August-Universität Göttingen](DE) and University of Auckland(NZ) have greatly improved the ability of complex computer simulations to describe this early epoch. They discovered that a complex network of structures can form in the first trillionth of a second after the Big Bang. The behaviour of these objects mimics the distribution of galaxies in today’s Universe.

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

    In contrast to today, however, these primordial structures are microscopically small. Typical clumps have masses of only a few grams and fit into volumes much smaller than present-day elementary particles. The results of the study have been published in the journal Physical Review D.

    The researchers were able to observe the development of regions of higher density that are held together by their own gravity. “The physical space represented by our simulation would fit into a single proton a million times over,” says Professor Jens Niemeyer, head of the Astrophysical Cosmology Group at the University of Göttingen. “It is probably the largest simulation of the smallest area of the Universe that has been carried out so far.” These simulations make it possible to calculate more precise predictions for the properties of these vestiges from the very beginnings of the Universe.

    Although the computer-simulated structures would be very short-lived and eventually “vaporise” into standard elementary particles, traces of this extreme early phase may be detectable in future experiments. “The formation of such structures, as well as their movements and interactions, must have generated a background noise of gravitational waves,” says Benedikt Eggemeier, a PhD student in Niemeyer’s group and first author of the study. “With the help of our simulations, we can calculate the strength of this gravitational wave signal, which might be measurable in the future.”

    It is also conceivable that tiny black holes could form if these structures undergo runaway collapse. If this happens they could have observable consequences today, or form part of the mysterious dark matter in the Universe. “On the other hand,” says Professor Easther, “If the simulations predict black holes form, and we don’t see them, then we will have found a new way to test models of the infant Universe.”

    See the full article here.

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    3

    The University of Auckland(NZ) is a public university based in Auckland, New Zealand. It is the highest ranked New Zealand university in the QS World University Rankings and Shanghai Jiao Tong Academic Ranking of World Universities. The institution was established in 1883 as a constituent college of the University of New Zealand. Originally it was housed in a disused courthouse. Today, the University of Auckland is New Zealand’s largest university by enrollment, hosting about 40,000 students on five Auckland campuses. The City Campus, in central Auckland, has the bulk of the students and faculties. There are eight faculties, including a law school, as well as three research institutes associated with the university.

    The University of Göttingen [Georg-August-Universität Göttingen] (DE) , is a public research university in the city of Göttingen, Germany. Founded in 1734 by George II, King of Great Britain and Elector of Hanover, and starting classes in 1737, the Georgia Augusta was conceived to promote the ideals of the Enlightenment. It is the oldest university in the state of Lower Saxony and the largest in student enrollment, which stands at around 31,600.

    Home to many noted figures, it represents one of Germany’s historic and traditional institutions. As of October 2020, 44 Nobel Prize winners have been affiliated with the University of Göttingen as alumni, faculty members or researchers.

    The University of Göttingen was previously supported by the German Universities Excellence Initiative, holds memberships to the U15 Group of major German research universities and to the Coimbra Group of major European research universities. Furthermore, the university maintains strong connections with major research institutes based in Göttingen, such as those of the Max Planck Society(DE) and the Leibniz Association [Leibniz-Gemeinschaft or Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz](DE). With approximately 9 million media units, the Göttingen State and University Library ranks among the largest libraries in Germany.

     
  • richardmitnick 9:14 pm on March 11, 2021 Permalink | Reply
    Tags: "Faster-Than-Light Travel Is Possible Within Einstein's Physics Astrophysicist Shows", , University of Göttingen [Georg-August-Universität Göttingen](DE), While pushing matter past the speed of light will always be a big no-no spacetime itself has no such rule.   

    From University of Göttingen [Georg-August-Universität Göttingen] via Science Alert(AU): “Faster-Than-Light Travel Is Possible Within Einstein’s Physics Astrophysicist Shows” 

    From University of Göttingen [Georg-August-Universität Göttingen]

    via

    ScienceAlert

    Science Alert(AU)

    11 MARCH 2021
    PETER DOCKRILL

    1
    Credit: dani3315/Getty Images.

    For decades, we’ve dreamed of visiting other star systems. There’s just one problem – they’re so far away, with conventional spaceflight it would take tens of thousands of years to reach even the closest one.

    Physicists are not the kind of people who give up easily, though. Give them an impossible dream, and they’ll give you an incredible, hypothetical way of making it a reality. Maybe.

    In a new study [Classical and Quantum Gravity]by physicist Erik Lentz from University of Göttingen [Georg-August-Universität Göttingen](DE), we may have a viable solution to the dilemma, and it’s one that could turn out to be more feasible than other would-be warp drives.

    This is an area that attracts plenty of bright ideas, each offering a different approach to solving the puzzle of faster-than-light travel: achieving a means of sending something across space at superluminal speeds.

    2
    Hypothetical travel times to Proxima Centauri, the nearest-known star to the Sun. Credit: E. Lentz.

    There are some problems with this notion, however. Within conventional physics, in accordance with Albert Einstein’s theories of relativity, there’s no real way to reach or exceed the speed of light, which is something we’d need for any journey measured in light-years.

    That hasn’t stopped physicists from trying to break this universal speed limit, though.

    While pushing matter past the speed of light will always be a big no-no spacetime itself has no such rule. In fact, the far reaches of the Universe are already stretching away faster than its light could ever hope to match.

    To bend a small bubble of space in a similar fashion for transport purposes, we’d need to solve relativity’s equations to create a density of energy that’s lower than the emptiness of space. While this kind of negative energy happens on a quantum scale, piling up enough in the form of ‘negative mass’ is still a realm for exotic physics.

    In addition to facilitating other kinds of abstract possibilities, such as wormholes and time travel, negative energy could help power what’s known as the Alcubierre warp drive.

    This speculative concept would make use of negative energy principles to warp space around a hypothetical spacecraft, enabling it to effectively travel faster than light without challenging traditional physical laws, except for the reasons explained above, we can’t hope to provide such a fantastical fuel source to begin with.

    But what if it were possible to somehow achieve faster-than-light travel that keeps faith with Einstein’s relativity without requiring any kinds of exotic physics that physicists have never seen?

    3
    Artistic impression of different spacecraft designs in ‘warp bubbles’. Credit:E. Lentz.

    In the new work, Lentz proposes one such way we might be able to do this, thanks to what he calls a new class of hyper-fast solitons – a kind of wave that maintains its shape and energy while moving at a constant velocity (and in this case, a velocity faster than light).

    According to Lentz’s theoretical calculations, these hyper-fast soliton solutions can exist within general relativity, and are sourced purely from positive energy densities, meaning there’s no need to consider exotic negative-energy-density sources that haven’t yet been verified.

    With sufficient energy, configurations of these solitons could function as ‘warp bubbles’, capable of superluminal motion, and theoretically enabling an object to pass through space-time while shielded from extreme tidal forces.

    It’s an impressive feat of theoretical gymnastics, although the amount of energy needed means this warp drive is only a hypothetical possibility for now.

    “The energy required for this drive traveling at light speed encompassing a spacecraft of 100 meters in radius is on the order of hundreds of times of the mass of the planet Jupiter,” Lentz says.

    “The energy savings would need to be drastic, of approximately 30 orders of magnitude to be in range of modern nuclear fission reactors.”

    While Lentz’s study claims to be the first known solution of its kind, his paper has arrived at almost exactly the same time as another recent analysis, published only this month [Classical and Quantum Gravity*], which also proposes an alternative model for a physically possible warp drive that doesn’t require negative energy to function.

    Both teams are now in contact, Lentz says, and the researcher intends to share his data further so other scientists can explore his figures. In addition, Lentz will be explaining his research in a week’s time – in a live YouTube presentation on March 19.


    Science Speaker Series: Dr. Erik Lentz. Scheduled for Mar 18, 2021.

    There are still plenty of puzzles to solve, but the free-flow of these kinds of ideas remains our best hope of ever getting a chance to visit those distant, twinkling stars.

    “This work has moved the problem of faster-than-light travel one step away from theoretical research in fundamental physics and closer to engineering,” Lentz says.

    “The next step is to figure out how to bring down the astronomical amount of energy needed to within the range of today’s technologies, such as a large modern nuclear fission power plant. Then we can talk about building the first prototypes.”

    The findings are reported in Classical and Quantum Gravity [*above] .

    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 University of Göttingen [Georg-August-Universität Göttingen], is a public research university in the city of Göttingen, Germany. Founded in 1734 by George II, King of Great Britain and Elector of Hanover, and starting classes in 1737, the Georgia Augusta was conceived to promote the ideals of the Enlightenment. It is the oldest university in the state of Lower Saxony and the largest in student enrollment, which stands at around 31,600.

    Home to many noted figures, it represents one of Germany’s historic and traditional institutions. As of October 2020, 44 Nobel Prize winners have been affiliated with the University of Göttingen as alumni, faculty members or researchers.

    The University of Göttingen was previously supported by the German Universities Excellence Initiative, holds memberships to the U15 Group of major German research universities and to the Coimbra Group of major European research universities. Furthermore, the university maintains strong connections with major research institutes based in Göttingen, such as those of the Max Planck Society and the Leibniz Association. With approximately 9 million media units, the Göttingen State and University Library ranks among the largest libraries in Germany.

     
  • richardmitnick 3:13 pm on February 25, 2021 Permalink | Reply
    Tags: "A tabletop waveguide delivers focused x rays", , Bright X-ray beams that are emitted in a single direction onto the target of interest are difficult to come by in a laboratory setting., , University of Göttingen [Georg-August-Universität Göttingen](DE), University of Göttingen [Georg-August-Universität Göttingen](DE) has now developed and demonstrated an approach for generating the radiation directly within a waveguide structure.,   

    From Physics Today: “A tabletop waveguide delivers focused x rays” 

    Physics Today bloc

    From Physics Today(US)

    25 Feb 2021
    Rachel Berkowitz

    By simultaneously generating and guiding beams, the layered anode emits x rays in one direction without the need for mirrors or large-scale accelerators.

    1
    Credit: University of Göttingen [Georg-August-Universität Göttingen](DE)/Julius Hilbig.

    Despite the widespread use of x rays as a fundamental tool for visualizing interior features of solid objects, bright X-ray beams that are emitted in a single direction onto the target of interest are difficult to come by in a laboratory setting. Unlike large-scale accelerators, which emit highly collimated beams, conventional small-scale sources generate x-ray radiation in all directions. Once they’re emitted, x rays cannot easily be manipulated with mirrors or lenses.

    To obtain bright x rays in a clearly defined path, Malte Vassholz and Tim Salditt of the University of Göttingen [Georg-August-Universität Göttingen](DE) have now developed and demonstrated an approach for generating the radiation directly within a waveguide structure. The layered material that makes up the waveguide emits x rays within a nanometers-wide channel, and the resulting beam’s brilliance exceeds that of a conventional µ-focus x-ray tube by two orders of magnitude. The method could lead to a tool for soft-matter imaging and coherent scattering experiments in laboratories.

    Laboratory-scale sources produce x rays by hitting a metal anode with electrons accelerated by a high voltage. Radiation is emitted at all angles when the atoms in the metal deflect and slow those electrons as well as when the electrons excite the metal atoms. To better control the angles at which a metal emits x rays, Vassholz and Salditt built a sandwich-like structure, illustrated in the figure, that was made up of a fluorescent metal layer embedded between guiding and cladding layers. Using a high-energy electron beam that was generated by an instrument adapted from an x-ray tube, the researchers excited the central metal layer, which caused it to emit x rays that were funneled into the guiding layers. Those beams traveled through the guiding layers and were emitted through the waveguide exit. A detector placed across from the exit showed sharp emission peaks corresponding to the waveguide modes, indicating that the device had effectively channeled x rays of up to 35 keV onto a target.

    Additional experiments and calculations suggested that the brightness of the emitted x rays could be further enhanced by using different metals or by varying the thickness of the layers. The researchers propose that the design could enable benchtop measurements of microscale structures that until now have only been accessible using synchrotron radiation. (M. Vassholz, T. Salditt, Sci. Adv. 7, eabd5677, 2021.)

    Science paper:
    Observation of electron-induced characteristic x-ray and bremsstrahlung radiation from a waveguide cavity
    Science Advances

    See the full article here .

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    Please help promote STEM in your local schools.

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    “Our mission

    The mission of Physics Today(US) is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
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