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Category: particle physics – Page 10

Self-interacting dark matter may solve three cosmic puzzles

A study led by UC Riverside physicist Hai-Bo Yu suggests that a new type of dark matter could explain three astrophysical puzzles across vastly different environments. Published in Physical Review Letters, the study proposes that dense clumps of self-interacting dark matter (SIDM)—each about a million times the mass of the sun—can account for unusual gravitational effects observed in gravitational lenses, stellar streams, and satellite galaxies.

Dark matter, which makes up about 85% of the universe’s matter, cannot be seen directly. The standard model assumes it is “cold” and collisionless, meaning that particles pass through one another without interacting. This model struggles, however, to explain certain high-density structures observed in the universe.

Yu’s work instead focuses on SIDM, in which dark matter particles collide and exchange energy. These interactions can trigger “gravothermal collapse,” forming extremely dense, compact cores.

High-resolution imaging captures cavity-induced density waves in a quantum gas

A new study, published in Physical Review Letters, reports that scientists have successfully imaged the formation of cavity-induced density waves induced by laser light in an ultracold quantum gas. Previously, only global signals, such as photon leakage or the peak in energy deposition of a fast charged particle (Bragg peaks), have been used to detect this kind of ordering. Prior to this study, there had been no direct, high-resolution in situ imaging of cavity-induced density-wave order in ultracold gases.

When laser light is arranged so that it bounces back and forth between two mirrors, light waves become trapped and create what is referred to as an optical cavity. This creates standing waves or amplifies light through resonance. When atoms in an ultracold unitary Fermi gas are placed in an optical cavity, they can absorb and emit this light. Unitary Fermi gases exist in a strongly interacting state where the wave scattering length makes interactions independent of the specific atomic details.

Light emitted by atoms in the gas can be absorbed by other atoms. This exchange of photons creates further interactions between the atoms that can cause a self-rearrangement into a periodic pattern within the gas, referred to as a density wave. This self-organization occurs above a critical threshold, called the superradiant phase transition, where the exchange of photons enables simultaneous, collective interaction among all atoms.

How nuclear batteries could speed the race to fusion power

Fusion reactions release tremendous amounts of energy by fusing two lighter atoms into a heavier one. But harvesting that energy has proven challenging. The most common approach is to heat water and spin a steam turbine, but that approach isn’t terribly efficient, harnessing at best around 60% of the power.

Avalanche Energy thinks it can capture more of that energy by developing new materials known as radiovoltaics. Radiovoltaics are similar to photovoltaics — traditional solar panels — in that they use semiconductors to transform radiation into electricity. They’ve been around for a while, but they’re not very effective. Existing radiovoltaics are easily damaged by the very radiation they harness and don’t produce that much electricity.

Today, Avalanche was awarded a $5.2 million contract from DARPA to develop new radiovoltaics, the company exclusively told TechCrunch.

Gravitational waves may be hidden in the light atoms emit

“Our findings may open a route toward compact gravitational-wave sensing, where the relevant atomic ensemble is millimeter-scale,” said Navdeep Arya, a postdoctoral researcher at Stockholm University. “A thorough noise analysis is necessary to assess practical feasibility, but our first estimates are promising.”

If confirmed, this approach could eventually lead to much smaller and more accessible detectors, offering a new way to observe some of the universe’s most dramatic events.

Universal surface-growth law confirmed in two dimensions after 40 years

Crystals, bacterial colonies, flame fronts: the growth of surfaces was first described in the 1980s by the Kardar–Parisi–Zhang equation. Since then, it has been regarded as a fundamental model in physics, with implications for mathematics, biology, and computer science.

Now—40 years later—a Würzburg-based research team from the Cluster of Excellence ctd.qmat has achieved the first experimental demonstration of KPZ behavior on 2D surfaces in space and time.

This was made possible by sophisticated materials engineering and a bold experimental approach: researchers injected polaritons—hybrid particles composed of light and matter—into the material. The results have been published in Science.

Dual-frequency Paul trap shows potential for synthesizing antihydrogen outside of CERN

A new type of radiofrequency trap can capture particles with extremely different requirements and could theoretically hold both types of particles at the same time. Researchers in the group of Professor Dmitry Budker from the PRISMA++ Cluster of Excellence and the Helmholtz Institute at Johannes Gutenberg University Mainz (JGU) were able to trap calcium ions or electrons in the same apparatus.

The team’s findings, published in Physical Review A, show the potential of this technology for synthesizing antihydrogen.

“Radiofrequency traps, also called Paul traps, have long been used by physicists to trap specific particles,” Dr. Hendrik Bekker explained. “However, they are usually limited to a single frequency.”

What if dark matter came in two states?

The absence of a signal could itself be a signal. This is the idea behind a new study published in the Journal of Cosmology and Astroparticle Physics, which aims to redefine how we search for dark matter, showing that it may not be necessary to find the same “clues” everywhere in order to interpret it.

In particular, the study suggests that even if we observe a certain type of signal at the center of our galaxy—an excess of gamma radiation that could result from the annihilation of dark matter particles—failing to detect the same signal in other systems, such as dwarf galaxies, is not enough to rule out this explanation.

Dark matter, in fact, may not consist of a single particle, but of multiple slightly different components, whose behavior varies depending on the cosmic environment.

Physicists zero in on the mass of the fundamental W boson particle

When fundamental particles are heavier or lighter than expected, physicists’ understanding of the universe can tip into the unknown. A particle that is just beyond its predicted mass can unravel scientists’ assumptions about the forces that make up all of matter and space. But now, a new precision measurement has reset the balance and confirmed scientists’ theories, at least for one of the universe’s core building blocks.

In a paper appearing in the journal Nature, an international team including MIT physicists reports a new, ultraprecise measurement of the mass of the W boson.

The W boson is one of two elementary particles that embody the weak force, which is one of the four fundamental forces of nature. The weak force enables certain particles to change identities, such as from protons to neutrons and vice versa. This morphing is what drives radioactive decay, as well as nuclear fusion, which powers the sun.

AI trained like a Rubik’s Cube solver simplifies particle physics equations

For years, Rutgers physicist David Shih solved Rubik’s Cubes with his children, twisting the colorful squares until the scrambled puzzle returned to order. He didn’t expect the toy to connect to his research, but recently he realized the logic behind the puzzle was exactly what he needed to solve a problem involving particle physics.

That idea led to a new artificial intelligence (AI) method that can simplify some of the extremely complex equations used in particle physics. Shih described the method in a study posted to the arXiv preprint server, a widely used site where scientists share new research.

“In reaching our solutions, we found that an analogy between mathematical simplification and solving Rubik’s Cubes was key,” said Shih, a professor in the Department of Physics and Astronomy at the Rutgers School of Arts and Sciences. “Both can be viewed as scrambling and unscrambling problems.”

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