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  • richardmitnick 12:52 pm on December 28, 2018 Permalink | Reply
    Tags: , , , Scientists propose a new model with dark energy and our universe riding on an expanding bubble in an extra dimension, , Uppsala University   

    From phys.org: “Our universe: An expanding bubble in an extra dimension” 

    physdotorg
    From phys.org

    December 28, 2018
    Uppsala University

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    In their article, the scientists propose a new model with dark energy and our universe riding on an expanding bubble in an extra dimension. Credit: Suvendu Giri

    Uppsala University researchers have devised a new model for the universe – one that may solve the enigma of dark energy. Their new article, published in Physical Review Letters, proposes a new structural concept, including dark energy, for a universe that rides on an expanding bubble in an additional dimension.

    We have known for the past 20 years that the universe is expanding at an ever accelerating rate. The explanation is the “dark energy” that permeates it throughout, pushing it to expand. Understanding the nature of this dark energy is one of the paramount enigmas of fundamental physics.

    It has long been hoped that string theory will provide the answer. According to string theory, all matter consists of tiny, vibrating “stringlike” entities. The theory also requires there to be more spatial dimensions than the three that are already part of everyday knowledge. For 15 years, there have been models in string theory that have been thought to give rise to dark energy. However, these have come in for increasingly harsh criticism, and several researchers are now asserting that none of the models proposed to date are workable.

    In their article, the scientists propose a new model with dark energy and our universe riding on an expanding bubble in an extra dimension. The whole universe is accommodated on the edge of this expanding bubble. All existing matter in the universe corresponds to the ends of strings that extend out into the extra dimension. The researchers also show that expanding bubbles of this kind can come into existence within the framework of string theory. It is conceivable that there are more bubbles than ours, corresponding to other universes.

    The Uppsala scientists’ model provides a new, different picture of the creation and future fate of the universe, while it may also pave the way for methods of testing string theory.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 10:51 am on June 21, 2016 Permalink | Reply
    Tags: , , New electron microscope method detects atomic-scale magnetism, , , Uppsala University   

    From ORNL: “New electron microscope method detects atomic-scale magnetism” 

    i1

    Oak Ridge National Laboratory

    June 20, 2016
    Morgan McCorkle, Communications
    mccorkleml@ornl.gov
    865.574.7308

    Scientists can now detect magnetic behavior at the atomic level with a new electron microscopy technique developed by a team from the Department of Energy’s Oak Ridge National Laboratory and Uppsala University, Sweden. The researchers took a counterintuitive approach by taking advantage of optical distortions that they typically try to eliminate.

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    ORNL’s Juan Carlos Idrobo helped develop an electron microscopy technique to measure magnetism at the atomic scale.

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    A new counterintuitive electron microscope approach can collect magnetic signals through the introduction of aberrations. The aberrated probe (right) results in imaging and spectra with lower spatial resolution than a traditionally corrected probe but can pick up a magnetic signature.

    “It’s a new approach to measure magnetism at the atomic scale,” ORNL’s Juan Carlos Idrobo said. “We will be able to study materials in a new way. Hard drives, for instance, are made by magnetic domains, and those magnetic domains are about 10 nanometers apart.” One nanometer is a billionth of a meter, and the researchers plan to refine their technique to collect magnetic signals from individual atoms that are ten times smaller than a nanometer.

    “If we can understand the interaction of those domains with atomic resolution, perhaps in the future we will able to decrease the size of magnetic hard drives,” Idrobo said. “We won’t know without looking at it.”

    Researchers have traditionally used scanning transmission electron microscopes to determine where atoms are located within materials. This new technique allows scientists to collect more information about how the atoms behave.

    “Magnetism has its origins at the atomic scale, but the techniques that we use to measure it usually have spatial resolutions that are way larger than one atom,” Idrobo said. “With an electron microscope, you can make the electron probe as small as possible and if you know how to control the probe, you can pick up a magnetic signature.”

    The ORNL-Uppsala team developed the technique by rethinking a cornerstone of electron microscopy known as aberration correction. Researchers have spent decades working to eliminate different kinds of aberrations, which are distortions that arise in the electron-optical lens and blur the resulting images.

    Instead of fully eliminating the aberrations in the electron microscope, the researchers purposely added a type of aberration, called four-fold astigmatism, to collect atomic level magnetic signals from a lanthanum manganese arsenic oxide material. The experimental study validates the team’s theoretical predictions presented in a 2014 Physical Review Letters study.

    “This is the first time someone has used aberrations to detect magnetic order in materials in electron microscopy,” Idrobo said. “Aberration correction allows you to make the electron probe small enough to do the measurement, but at the same time we needed to put in a specific aberration, which is opposite of what people usually do.”

    Idrobo adds that new electron microscopy techniques can complement existing methods, such as x-ray spectroscopy and neutron scattering, that are the gold standard in studying magnetism but are limited in their spatial resolution.

    The study is published as Detecting magnetic ordering with atomic size electron probes, in the journal of Advanced Structural and Chemical Imaging. Coauthors are ORNL’s Juan Carlos Idrobo, Michael McGuire, Christopher Symons, Ranga Raju Vatsavai, Claudia Cantoni and Andrew Lupini; and Uppsala University’s Ján Rusz and Jakob Spiegelberg.

    The electron microscopy experiments were conducted at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL. The research was supported by DOE’s Office of Science.

    See the full article here .

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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