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Category: physics

Physicists figure out how to reduce formation of ‘viscous fingers’

When they reach the bottom of a soap dispenser, frugal handwashers might try adding water to the bottle to push out the last bit of soap. But usually, the water drills right through the soap and jets out an only slightly sudsy splash.

This happens because when you push a less viscous fluid like water into a more viscous fluid like soap in a confined space, the place where the two fluids meet can be unstable, and the runnier liquid might find a path of least resistance.

If you look very closely, you might see tiny protuberances form at the place where the fluids touch, in a phenomenon physicists call “viscous fingering.” In certain types of confined spaces, the fingers form a branching pattern.

Using pulsars as ultra-precise gravitational probes to ‘weigh’ neighboring galaxies

Researchers at The University of Alabama in Huntsville (UAH), a part of The University of Alabama System, have identified a promising new method for measuring the mass of galaxies orbiting the Milky Way by using pulsars, some of the universe’s most precise natural clocks, to detect tiny gravitational effects across our galaxy.

The work, published on the arXiv preprint server, offers a novel approach for studying the hidden dark matter contained within nearby satellite galaxies. The findings could have broad implications for astrophysics and cosmology.

The study was authored by UAH astrophysicists Dr. Thomas Donlon, postdoctoral research assistant II, and Dr. Sukanya Chakrabarti, a professor and Pei-Ling Chan Endowed Chair in the College of Science, in collaboration with Dr. Jason A. S. Hunt, an astrophysicist at the University of Surrey, U.K. The research examines how the gravitational pull of neighboring dwarf galaxies subtly disturbs the Milky Way.

Better helium reporting to improve fission and fusion materials modeling

Standardizing calculations of the helium byproducts generated in advanced fission and fusion energy system materials can increase reactor safety and longevity, according to a study led by University of Michigan Engineering with collaborators at Oak Ridge National Laboratory and its management contractor UT-Battelle.

Through a series of simulations, the researchers found that modeling assumptions and key alloy elements—like carbon, nitrogen and nickel—significantly influence helium generation predictions. If left unaddressed, excess helium in real-world reactors could lead to faster component failure as materials swell and become brittle.

“If used, our reporting methods will improve the experimental and modeling fidelity of the nuclear materials databases being generated both domestically and internationally, driving the rapid deployment of advanced nuclear,” said Kevin Field, a professor of nuclear engineering and radiological sciences at U-M and corresponding author of the study published in the Journal of Physics: Energy.

Researchers solve longstanding problem in measuring semiconductor defects

Researchers at Sandia National Laboratories and Auburn University have developed a new method to more accurately detect atomic-scale defects in electronic materials, an advance that could help improve technologies ranging from electric vehicles to high-power electronics. The study, appearing in the Journal of Applied Physics, addresses a longstanding challenge in understanding what happens at the critical boundary where a semiconductor meets an insulating layer.

At this interface, microscopic defects can trap electrical charge and quietly reduce device performance, even when the device otherwise appears to function normally. These defects can limit efficiency, increase electrical losses, and reduce the performance of advanced semiconductor devices.

Scientists commonly study these defects by comparing how a device responds to slow and fast electrical signals. However, the technique depends on knowing a key device property, the insulator capacitance, with very high accuracy. Even tiny errors can produce misleading results, sometimes making it appear that far more defects exist than are actually present.

Busseiron and the formation of a discipline in Japanese physics

The middle of the twentieth century was a period of significant scientific advancement, particularly in the realm of physics. Within this rapidly changing landscape, academic disciplines emerged and evolved to keep pace with scientific discoveries. The new subdiscipline of solid-state physics gained prominence in the United States, but it was later subsumed by the broader category of condensed matter physics.

In Japan, however, physics research since the 1940s has included a unique branch called Busseiron—a discipline concerning the study of matter that has no direct English equivalent but that has remained in use nonetheless.

A new article by Hiroto Kono in Isis: A Journal of the History of Science Society explores the historical formation of Busseiron and how it was shaped by its specific national context.

Gleaning Information from Noise

Researchers derive a universal limit linking noise and response to perturbations in systems far from equilibrium.

Noise comes in many forms. A microscopic bead twitches in an optical trap; voltage fluctuations flicker through a circuit. But it’s not only a nuisance. Since 1966, physicists have understood that for systems in thermal equilibrium, such randomness also gives valuable information: Spontaneous fluctuations and the system’s response to external perturbations are locked together, frequency by frequency, according to the so-called fluctuation–dissipation theorem (FDT) [1]. That link is the basis of noise-based thermometry, microrheology, and many calibration methods. But thermal equilibrium is rare in the real world. Rather, most physical and biological systems are driven by an external force, fed, or alive, with energy continually flowing through them.

Dark lunar craters could host ultrastable lasers for moon navigation

They rank among the darkest and coldest places in the solar system: Hundreds of lunar craters, many of them at the moon’s south pole, never receive direct sunlight and lie in permanent shadow. That’s exactly why physicist Jun Ye and his colleagues suggest that these craters are the perfect place to build a critical component for an ultrastable laser.

On the moon, a highly stable laser—a source of coherent light that has a nearly unwavering frequency, or color—could provide a master time signal and offer GPS-like lunar navigation, said Ye, who is affiliated with both the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder. Multiple copies of these lunar lasers could precisely measure the distances between objects and potentially detect exotic physics phenomena such as ripples in spacetime.

To construct a lunar laser, astronauts would first install a key component known as an optical silicon cavity —a block of silicon that permits only certain frequencies of light to bounce back and forth between mirrors on each end of the block. The distance between the two mirrors determines the frequencies that are allowed to resonate; for a highly stable optical cavity, that distance, and therefore those frequencies, does not vary.

Learning physics can derail some students: New research shows the best way to keep them on track

For many undergraduate students, exploring the complexities of physics for the first time, from wading through advanced mathematics, to absorbing information in a large lecture format, can be a daunting endeavor—one that dissuades many students from continuing their studies.

Educators have known for some time that students tend to learn these subjects better in hands-on, or “active learning,” environments—but some are more effective than others.

AI shapes the design of the electron-ion collider

Artificial intelligence and machine learning are shaping major design and research decisions for the planned Electron-Ion Collider (EIC), a next-generation nuclear physics research facility that will collide electrons with protons or nuclei to probe matter’s structure.

The EIC—being built at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory in partnership with DOE’s Thomas Jefferson National Accelerator Facility (Jefferson Lab)—will reveal the inner structure of matter in unprecedented detail. It is the world’s first collider designed with AI and machine learning integrated into both its accelerator and detector systems.

“EIC is a new facility that can take advantage of AI and machine learning from the start,” said Tanja Horn, a professor of physics at The Catholic University of America, and co-chair of AI4EIC, a working group devoted to developing AI for the EIC. “A wide array of AI tools is now available—perfectly timed for the EIC.”

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