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Category: physics

Machine learning outpaces supercomputers for simulating galaxy evolution coupled with supernova explosion

Researchers have used machine learning to dramatically speed up the processing time when simulating galaxy evolution coupled with supernova explosion. This approach could help us understand the origins of our own galaxy, particularly the elements essential for life in the Milky Way.

The findings are published in The Astrophysical Journal.

The team was led by Keiya Hirashima at the RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) in Japan, along with colleagues from the Max Planck Institute for Astrophysics (MPA) and the Flatiron Institute.

Record-breaking material emits infrared light better than it absorbs it, without violating the laws of physics

New results published in the journal Physical Review Letters detail how a specially designed metamaterial was able to tip the normally equal balance between thermal absorption and emission, enabling the material to better emit infrared light than absorb it.

At first glance, these findings appear to violate Kirchhoff’s law of , which states that—under specific conditions—an object will absorb (absorptivity) in one direction and emit it (emissivity) with equal intensity in another, a phenomenon known as reciprocity.

Over the past decade, however, scientists have begun exploring theoretical designs that, under the right conditions, could allow materials to break reciprocity. Understanding how a material absorbs and emits infrared light (heat) is central to many fields of science and engineering. Controlling how a material absorbs and emits infrared light could pave the way for advances in harvesting, thermal cloaking devices, and other technologies.

Hans Bethe — Biographical

Hans Albrecht Bethe was born in Strasbourg, Alsace-Lorraine, on July 2 1906. He attended the Gymnasium in Frankfurt from 1915 to 1924. He then studied at the University of Frankfurt for two years, and at Munich for two and one half years, taking his Ph. D. in theoretical physics with Professor Arnold Sommerfeld in July 1928.

He then was an Instructor in physics at Frankfurt and at Stuttgart for one semester each. From fall 1929 to fall 1933 his headquarters were the University of Munich where he became Privatdozent in May 1930. During this time he had a travel fellowship of the International Education Board to go to Cambridge, England, in the fall of 1930, and to Rome in the spring terms of 1931 and 1932. In the winter semester of 1932–1933,he held a position as Acting Assistant Professor at the University of Tubingen which he lost due to the advent of the Nazi regime in Germany.

Bethe emigrated to England in October 1933 where he held a temporary position as Lecturer at the University of Manchester for the year 1933–1934, and a fellowship at the University of Bristol in the fall of 1934. In February 1935 he was appointed Assistant Professor at Cornell University, Ithaca, N. Y. U.S.A., then promoted to Professor in the summer of 1937. He has stayed there ever since, except for sabbatical leaves and for an absence during World War II. His war work took him first to the Radiation Laboratory at the Massachusetts Institute of Technology, working on microwave radar, and then to the Los Alamos Scientific Laboratory which was engaged in assembling the first atomic bomb. He returned to Los Alamos for half a year in 1952. Two of his sabbatical leaves were spent at Columbia University, one at the University of Cambridge, and one at CERN and Copenhagen.

AI and biophysics unite to forecast high-risk viral variants before outbreaks

When the first reports of a new COVID-19 variant emerge, scientists worldwide scramble to answer a critical question: Will this new strain be more contagious or more severe than its predecessors? By the time answers arrive, it’s frequently too late to inform immediate public policy decisions or adjust vaccine strategies, costing public health officials valuable time, effort, and resources.

In a pair of recent publications in Proceedings of the National Academy of Sciences, a research team in the Department of Chemistry and Chemical Biology combined biophysics with artificial intelligence to identify high-risk viral variants in record time—offering a transformative approach for handling pandemics. Their goal: to get ahead of a virus by forecasting its evolutionary leaps before it threatens public health.

“As a society, we are often very unprepared for the emergence of new viruses and pandemics, so our lab has been working on ways to be more proactive,” said senior author Eugene Shakhnovich, Roy G. Gordon Professor of Chemistry. “We used fundamental principles of physics and chemistry to develop a multiscale model to predict the course of evolution of a particular variant and to predict which variants will become dominant in populations.”

High-velocity molecular clouds in M83 provide new insight into how galaxies evolve

A new result from the molecular gas survey in the Southern Pinwheel Galaxy M83 using the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope reveals a discovery of 10 high-velocity clouds composed of molecular gas, moving at velocities significantly different from M83’s overall rotation, an indication that the influx of these gases—which help to form stars—are from outside the galaxy.

This survey is led by Jin Koda, professor in the Department of Physics and Astronomy in the College of Arts and Sciences at Stony Brook University, who collaborated with Maki Nagata and Fumi Egusa, of the University of Tokyo, as well as an international team of astrophysicists. Their findings are published in The Astrophysical Journal.

Galaxies are primarily composed of stars and gas, with gas serving as the material for forming new stars. Through this process of star formation, galaxies evolve by converting gas into stars. It is estimated that without a supply of gas from external sources, the existing gas in a galaxy would be consumed within about 1 billion years and star formation would cease. The team’s finding on the of M83 provides new insight into how galaxies may evolve over millions and billions of years.

Breaking Ohm’s law: Nonlinear currents emerge in symmetry-broken materials

In a review just published in Nature Materials, researchers take aim at the oldest principle in electronics: Ohm’s law.

Their article, “Nonlinear transport in non-centrosymmetric systems,” brings together rapidly growing evidence that, when a material lacks inversion symmetry, the familiar linear relation between current and voltage can break down, giving rise to striking quadratic responses.

The study was led by Manuel Suárez-Rodríguez—working under the guidance of Ikerbasque Professors Fèlix Casanova and Luis E. Hueso at CIC nanoGUNE, together with Prof. Marco Gobbi at the Materials Physics Center (CFM, CSIC-UPV/EHU).

Breaking the Rules of Magnetism: Unusual Crystal Surprises Physicists With Cooling Effect

The research team has identified atacamite as a material with magnetocaloric properties. Natural crystals have long captivated us with their vivid colors, flawless geometry, and striking symmetry. But for scientists, these beautiful formations offer more than just visual delight. Hidden within thei

Physicists Catch Light in ‘Imaginary Time’ in Scientific First

For the first time, researchers have seen how light behaves during a mysterious phenomenon called ‘imaginary time’

When you shine light through almost any transparent material, the gridlock of electromagnetic fields that make up the atomic alleys and side streets will add a significant amount of time to each photon’s commute.

This delay can tell physicists a lot about how light scatters, revealing details about the matrix of material the photons must navigate. Yet until now, one trick up the theorist’s sleeve for measuring light’s journey – invoking imaginary time – has not been fully understood in practical terms.