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RHIC data reveal intriguing dip in momentum fluctuations in high-density nuclear matter

Scientists using the STAR detector to study particle collisions at the Relativistic Heavy Ion Collider (RHIC) have found an intriguing dip in their data in a relatively unexplored region of the nuclear phase diagram—a map of how nuclear matter behaves under various conditions of temperature and density. The dip appears in data tracking collision-by-collision variations in the momenta of particles emerging from collisions between gold nuclei at RHIC, near RHIC’s lowest collision energies. These collisions create the highest-density nuclear matter and may indicate that something interesting is happening in that dense region of the phase diagram. The findings are described in a paper just published in Physical Review Letters.

RHIC, which operated as a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at DOE’s Brookhaven National Laboratory from 2000 to 2026, was designed to create exotic forms of matter, including the quark-gluon plasma that existed in the very early universe and matter that approaches the density of neutron stars. A dip in the momentum fluctuations—which are closely tied to the temperature of the matter—may be a sign that the way nuclei transform into these exotic substances changes character at RHIC’s lower energies.

Exploring whether such a change in transition behavior exists—and, if so, where a hypothesized “critical point” demarcating this change is located on the nuclear phase diagram—has been a long-sought goal of physicists conducting research at RHIC.

Carbon nanotube foams reveal a new kind of mechanical memory

In their earliest years of development, computers used mechanical gears and levers to store information. Today, researchers are exploring whether a material itself can hold onto information, storing memory in how it bends and springs back to its original shape.

Through new research published in Physical Review X, Ramathasan Thevamaran and colleagues at the University of Wisconsin–Madison have discovered a material that takes this concept a step further: a foam made of carbon nanotubes that remembers exactly how hard it was squeezed, then returns to its original shape with no lasting damage.

Electrical control method tunes magnetic properties for next-generation spintronic memory

A research team led by Professor Jung-Il Hong of the Department of Physics and Chemistry at DGIST has successfully used current pulses to alter the spin configuration within a ferrimagnetic material, lowering its “compensation temperature”—the temperature at which opposing magnetizations cancel each other out—by up to approximately 110 K.

The research is published in the journal Advanced Functional Materials.

The team controlled the material’s magnetic properties using only electrical signals, without changing the composition or thickness of the alloy. The technology could have applications in next-generation spintronic memory devices.

The secret to a perfect crystal may be a precisely calibrated extra turn

Creating a perfect crystal sounds straightforward: Arrange identical building blocks into a repeating, orderly structure. At the microscopic scale, though, even subtle biases in how particles interact can push them in preferred directions, making it harder to form uniform crystalline materials.

A Rice University-led study offers a way around that problem. Tanaka Tatsuya, a visiting Rice research scientist from Kao Corp. in Japan, has developed a theoretical strategy for eliminating an unintended directional bias that can arise when magnetic particles are assembled using rotating magnetic fields. The work, published in Physical Review Research, shows the solution can be surprisingly simple: Rotate the magnetic field slightly more than one full turn before reversing its direction.

“When we rotate the magnetic field, the magnetic response of the particle is always slightly behind,” said Sibani Lisa Biswal, chair of chemical and biomolecular engineering and the William M. McCardell Professor in Chemical Engineering at Rice and the corresponding author of the study. “That tiny delay turns out to matter. It can create a preferred direction for assembly even when the applied field appears perfectly symmetric.”

Physicists crack the math connecting ultraslow quantum magnetism to ultrafast black-hole physics

A team led by University at Buffalo physicists has found a mathematical solution that shows how a frustrated quantum magnet can transition from ultraslow behavior to ultrafast, highly entangled behavior resembling that of a black hole.

Their solution connects spin glasses—states of matter in which atomic magnets point in disordered directions and become effectively frozen in place—to the fast, entangled states of matter described by the Sachdev-Ye-Kitaev (SYK) model that’s been used to study black hole physics, quantum chaos and other exotic phenomena.

“We’ve essentially found the math that describes how matter can go from among the slowest states in quantum dynamics to among the fastest,” says Jamir Marino, Ph.D., assistant professor of physics in the UB College of Arts and Sciences and senior author of the team’s study, which was published Sept. 17 in Physical Review Letters.

From swarming bacteria to tissue cells, living matter defies classic physical models of motion

A new study led by researchers from Ben-Gurion University of the Negev (BGU) reveals that living matter violates previously known physical principles of symmetry when cellular flows form and break down collective patterns. The research, published in Nature Physics, challenges conventional liquid-crystal physics by showing that moving single-celled bacteria and human respiratory cells spontaneously break mirror symmetry, moving in curved, irreversible spiral paths.

The collaborative study was led by Professors Avraham Be’er and Victor Yashunsky from BGU’s Jacob Blaustein Institutes for Desert Research (Sede Boqer Campus) and Department of Physics, alongside Professor Gil Ariel from Bar-Ilan University and Professor D. J. G. Pearce from the University of Geneva.

Astronomers Just Caught a Giant Planet in the Act of Forming

Astronomers have confirmed the youngest known planet, a Jupiter-size baby world less than a million years old that formed far faster than expected.

Astronomers have confirmed the youngest known planet ever observed, a world less than 1 million years old that is still surrounded by the material from which it formed. Known as Elias 2–24 b, the young planet remains embedded in a swirling disk of gas and dust around its host star.

Its extreme youth is forcing researchers to reconsider how quickly large planets can take shape.

Two Dead Stars Are Racing Around Each Other Every 6.2 Minutes

A pair of white dwarfs race around each other every 374 seconds, creating a rhythmic X-ray beacon that could reveal powerful gravitational waves.

Every 6.2 minutes, two dead stars complete an entire orbit around each other.

The system, eRASSU J060839.5–704014, or eRASSU J0608, is so compact that material from one white dwarf appears to strike the other directly, producing a strong X-ray pulse on every orbit. Astronomers have now found that the orbit is also shrinking unusually fast, making the system a promising target for future gravitational wave observatories.

Stress Hormone Cortisol Rewires the Brain to Strengthen Emotional Memories

Cortisol strengthens emotional memories by reshaping how brain networks for emotion and memory work together.

Stress does not strengthen every memory equally. New research suggests that cortisol, a hormone released during stressful situations, changes brain activity in ways that strengthen memories of experiences a person finds emotionally intense.

Yale researchers found that cortisol affected two distinct brain networks, one associated with emotional intensity and another with memory formation. It also increased coordination between them, offering a more detailed explanation for how stress can strengthen emotional memories.

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