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  • richardmitnick 11:46 am on September 26, 2021 Permalink | Reply
    Tags: "One of nature’s key constants is much larger in a quantum material", , "Spinons", , If the fine-structure constant throughout the cosmos were as large as the one in quantum spin ices “the periodic table would only have 10 elements., , , Quantum spin ices are a class of substances in which particles can’t agree., The fine-structure constant, The fine-structure constant is about 10 times its normal value in a type of material called quantum spin ice., The impasse occurs because of the materials’ geometry: The particles are located at the corners of an array of pyramids that are connected at the corners., Unfortunately scientists haven’t yet found a material that definitively qualifies as quantum spin ice.   

    From “Science News (US) : “One of nature’s key constants is much larger in a quantum material” 

    From “Science News (US)

    September 21, 2021
    Emily Conover

    1
    Particles with the quantum property called spin, illustrated by the blue arrow, can’t agree on an orientation in a type of material called quantum spin ice. Credit: ELLA MARU STUDIO/Science Source.

    The fine-structure constant is about 10 times its normal value in a type of material called quantum spin ice, physicists calculate in the Sept. 10 Physical Review Letters. The new calculation hints that quantum spin ice could give a glimpse at physics within an alternate universe where the constant is much larger.

    With an influence that permeates physics and chemistry, the fine-structure constant sets the strength of interactions between electrically charged particles. Its value, about 1/137, consternates physicists because they can’t explain why it has that value, even though it is necessary for the complex chemistry that is the basis of life (SN: 11/2/16).

    If the fine-structure constant throughout the cosmos were as large as the one in quantum spin ices “the periodic table would only have 10 elements,” says theoretical physicist Christopher Laumann of Boston University (US). “And it probably would be hard to make people; there wouldn’t be enough richness to chemistry.”

    Quantum spin ices are a class of substances in which particles can’t agree. The materials are made up of particles with spin, a quantum version of angular momentum, which makes them magnetic. In a normal material, particles would come to a consensus below a certain temperature, with the magnetic poles lining up in either the same direction or in alternating directions. But in quantum spin ices, the particles are arranged in such a way that the magnetic poles, or equivalently the spins, can’t agree even at a temperature of absolute zero (SN: 2/13/11).

    The impasse occurs because of the materials’ geometry: The particles are located at the corners of an array of pyramids that are connected at the corners. Conflicts between multiple sets of neighbors mean that the closest these particles can get to harmony is arranging themselves so that two spins face out from each pyramid, and two face in.

    2
    In quantum spin ices, particles (black dots) are located at the corners of an array of pyramids (red). Normally, the spins of the particles (green arrows) arrange so that two are pointing into the pyramid and two out. If that rule is broken, as illustrated, quasiparticles called spinons (orange and blue) form.S.D. Pace et al/PRL 2021.

    This uneasy truce can give rise to disturbances that behave like particles within the material, or quasiparticles (SN: 10/3/14). Flip particles’ spins around and you can get what are called spinons, quasiparticles that can move through the material and interact with other spinons in a manner akin to electrons and other charged particles found in the world outside the material. The material re-creates the theory of quantum electrodynamics, the piece of particles physics’ standard model that hashes out how electrically charged particles do their thing. But the specifics, including the fine-structure constant, don’t necessarily match those in the wider universe.

    So Laumann and colleagues set out to calculate the fine-structure constant in quantum spin ices for the first time. The team pegged the number at about 1/10, instead of 1/137. What’s more, the researchers found that they could change the value of the fine-structure constant by tweaking the properties of the theoretical material. That could help scientists study the effects of altering the fine-structure constant — a test that’s well out of reach in our own universe, where the fine-structure constant is fixed.

    Unfortunately scientists haven’t yet found a material that definitively qualifies as quantum spin ice. But one much-studied prospect is a group of minerals called pyrochlores, which have magnetic ions, or electrically charged atoms, arranged in the appropriate pyramid configuration. Scientists might also be able to study the materials using a quantum computer or another quantum device designed to simulate quantum spin ices (SN: 6/29/17).

    If scientists succeed in creating quantum spin ice, the materials could reveal how quantum electrodynamics and the standard model would work in a universe with a much larger fine-structure constant. “That would be the hope,” says condensed matter theorist Shivaji Sondhi of the University of Oxford, who was not involved with the research. “It’s interesting to be able to make a fake standard model … and ask what would happen.”

    See the full article here .


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  • richardmitnick 1:26 pm on December 2, 2020 Permalink | Reply
    Tags: "Researchers improve the measurement of a fundamental physical constant", , , Characterization of the strength of interaction between light and charged elementary particles such as electrons., , , The fine-structure constant, The use of more accurate constants can help to answer fundamental questions such as the origin of dark matter in the universe.   

    From Centre National de la Recherche Scientifique [CNRS ](FR) via phys.org: “Researchers improve the measurement of a fundamental physical constant” 

    CNRS bloc

    From Centre National de la Recherche Scientifique [CNRS ](FR)

    1
    Illustration of the experimental measurement of the fine-structure constant. The background patterns in the image represent the actual Feynman diagrams used to help calculate the theoretical value of the electron magnetic moment anomaly (calculated using the fine-structure constant, among others). The scheme of the atom interferometer used for measuring the recoil velocity is represented in colour. Credit: Pierre Cladé, Saïda Guellati-Khélifa et Tatsumi Aoyama.

    The validation and application of theories in physics require the measurement of universal values known as fundamental constants.

    A team of French researchers has just conducted the most accurate measurement to date of the fine-structure constant, which characterizes the strength of interaction between light and charged elementary particles, such as electrons.

    This value has just been determined with an accuracy of 11 significant digits; improving the precision of the previous measurement by a factor of 3.

    The scientists achieved such precision by enhancing their experimental set-up, in an effort to reduce inaccuracies and to control effects that can create perturbations of the measurement.

    The experiment involves cold rubidium atoms with a temperature approaching absolute zero.

    When they absorb photons, these atoms recoil at a velocity that depends on their mass. The highly precise measurement of this phenomenon helps to improve the knowledge of the fine-structure constant.

    These results, which will appear in Nature on 3 December, open new prospects for testing the Standard Model’s theoretical predictions.

    The use of more accurate constants can help to answer fundamental questions, such as the origin of dark matter in the universe.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    CNRS (FR) campus via Glassdoor

    CNRS (FR) encourages collaboration between specialists from different disciplines in particular with the university thus opening up new fields of enquiry to meet social and economic needs. CNRS has developed interdisciplinary programs which bring together various CNRS departments as well as other research institutions and industry.

    Interdisciplinary research is undertaken in the following domains:

    Life and its social implications
    Information, communication and knowledge
    Environment, energy and sustainable development
    Nanosciences, nanotechnologies, materials
    Astroparticles: from particles to the Universe

     
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