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Category: physics – Page 68

What can the night sky tell us about the expansion of the universe?

It’s a loaded question, one that researchers across the globe have been trying to answer for decades. Since 2013, they’ve been helped by the Dark Energy Survey (DES), a collaboration of more than 400 scientists at 25 institutions. At Penn, this includes Masao Sako, Arifa Hasan Ahmad and Nada Al Shoaibi Presidential Professor of Physics and Astronomy; Bhuvnesh Jain, Walter H. and Leonore C. Annenberg Professor in the Natural Sciences; Gary Bernstein, Reese W. Flower Professor of Astronomy and Astrophysics; and a handful of others from the Department of Physics & Astronomy.

In 2019, the DES finished collecting data, but analysis and discoveries continue, including one that Sako and colleagues announced recently in which they validated the “cosmic acceleration” model and dark energy’s role in it. That research is one of five recent studies detailed below, in this second iteration of Omnia’s new research roundup.

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Topological wave structures are wave patterns that exhibit specific topological properties, or in other words, properties that remain unvaried under smooth deformations of a physical system. These structures, such as vortices and skyrmions, have attracted significant attention within the physics research community.

While physicists have carried out extensive studies focusing on topological wave structures in various wave systems, surprisingly their most classical example remains unexplored. These are water waves, oscillations or disturbances that propagate on the surface of water or other fluid.

Researchers at RIKEN recently set out to fill this gap in the literature, by offering a description of various water-wave topological structures. Their paper, published in Physical Review Letters, offers a theoretical framework that could inform future experiments aimed at emulating topological wave phenomena.

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Scientists are getting a more detailed look than ever before at the electrons they use in precision experiments.

Nuclear physicists with the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility have shattered a nearly 30-year-old record for the measurement of parallel spin within an electron beam – or electron beam polarimetry, for short. The achievement sets the stage for high-profile experiments at Jefferson Lab that could open the door to new physics discoveries.

In a peer-reviewed paper published in the journal Physical Review C (“Ultrahigh-precision Compton polarimetry at 2 GeV”), a collaboration of Jefferson Lab researchers and scientific users reported a measurement more precise than a benchmark achieved during the 1994–95 run of the SLAC Large Detector (SLD) experiment at the SLAC National Accelerator Laboratory in Menlo Park, California.

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In a recent development at Fudan University, a team of applied mathematicians and AI scientists has unveiled a cutting-edge machine learning framework designed to revolutionize the understanding and prediction of Hamiltonian systems. The paper is published in the journal Physical Review Research.

Named the Hamiltonian Neural Koopman Operator (HNKO), this innovative framework integrates principles of mathematical physics to reconstruct and predict Hamiltonian systems of extremely-high dimension using noisy or partially-observed data.

The HNKO framework, equipped with a unitary Koopman structure, has the remarkable ability to discover new conservation laws solely from observational data. This capability addresses a significant challenge in accurately predicting dynamics in the presence of noise perturbations, marking a major breakthrough in the field of Hamiltonian mechanics.

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Time’s inexorable march might well wait for no one, but a new experiment by researchers at the Technical University of Darmstadt in Germany and Roskilde University in Denmark shows how in some materials it might occasionally shuffle.

An investigation into the way substances like glass age has uncovered the first physical evidence of a material-based measure of time being reversible.

For the most part the laws of physics care little about time’s arrow. Flip an equation describing the movement of an object and you can easily calculate where it started. We describe such laws as time reversible.

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Physicists at Paderborn University have enhanced solar cell efficiency significantly using tetracene, an organic material, based on complex computer simulations. They discovered that defects at the tetracene-silicon interface boost energy transfer, promising a new solar cell design with drastically improved performance.

Physicists at Paderborn University have used complex computer simulations to create a novel solar cell design that boasts substantially higher efficiency than existing options. The enhancement in performance is attributed to a slender coating of an organic compound named tetracene. The results have recently been published in the renowned journal Physical Review Letters.

“The annual energy of solar radiation on Earth amounts to over one trillion kilowatt-hours and thus exceeds the global energy demand by more than 5,000 times. Photovoltaics, i.e. the generation of electricity from sunlight, therefore offers a large and still largely untapped potential for the supply of clean and renewable energy. Silicon solar cells used for this purpose currently dominate the market, but have efficiency limits,” explains Prof Dr Wolf Gero Schmidt, physicist and Dean of the Faculty of Natural Sciences at Paderborn University. One reason for this is that some of the energy from short-wave radiation is not converted into electricity, but into unwanted heat.

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Supernovae–stellar explosions as bright as an entire galaxy–have fascinated us since time immemorial. Yet, there are more hydrogen-poor supernovae than astrophysicists can explain. Now, a new Assistant Professor at the Institute of Science and Technology Austria (ISTA) has played a pivotal role in identifying the missing precursor star population. The results, now published in Science, go back to a conversation the involved professors had many years ago as junior scientists.

The Enigma of Hydrogen-Poor Supernovae

Some stars do not simply die down, but explode in a stellar blast that could outshine entire galaxies. These cosmic phenomena, called supernovae, spread light, elements, energy, and radiation in space and send galactic shock waves that could compress gas clouds and generate new stars. In other words, supernovae shape our universe. Among these, hydrogen-poor supernovae from exploding massive stars have long puzzled astrophysicists. The reason: scientists have not been able to put their finger on their precursor stars. It is almost as if these supernovae appeared out of nowhere.

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