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Category: particle physics

The persistence of gravitational wave memory

Neutron stars are ultra-dense remnants of massive stars that collapsed after supernova explosions and are made up mostly of subatomic particles with no electric charge (i.e., neutrons). When two neutron stars collide, they are predicted to produce gravitational waves, ripples in the fabric of spacetime that travel at the speed of light.

Gravitational waves typically take the form of oscillations, periodically and temporarily influencing the universe’s underlying fabric (i.e., spacetime). However, general relativity suggests that for some cosmological events, in addition to the oscillatory displacement of test masses (as produced by the passage of a gravitational wave train), there exists a final permanent displacement of them via a phenomenon referred to as “gravitational wave memory.”

Researchers at the University of Illinois at Urbana-Champaign, the Academy of Athens, the University of Valencia and Montclair State University recently carried out a study exploring the gravitational wave memory effects that would arise from neutron star mergers.

Atom-thin electronics withstand space radiation, potentially surviving for centuries in orbit

Atom-thick layers of molybdenum disulfide are ideally suited for radiation-resistant spacecraft electronics, researchers in China have confirmed. In a study published in Nature, Peng Zhou and colleagues at Fudan University put a communications system composed of the material through a gauntlet of rigorous tests—including the transmission of their university’s Anthem—confirming that its performance is barely affected in the harsh environment of outer space.

Beyond the protection of Earth’s magnetic field, the electronic components of modern spacecraft are extremely vulnerable to constant streams of cosmic rays and heavy ions. While onboard systems can be shielded with radiation-protective materials, this approach takes up valuable space and adds weight to spacecraft.

That extra mass drives up launch costs and can limit the payload available for scientific instruments or communications hardware. A far better solution would be to fabricate the electronics themselves from materials that are intrinsically resistant to radiation damage.

Neutron scattering helps clarify magnetic behavior in altermagnetic material

Scientists at the U.S. Naval Research Laboratory (NRL) have identified the true source of a magnetic effect seen in the material ruthenium dioxide (RuO₂), helping resolve an active debate in the rapidly growing field of altermagnetism. The study is published in the journal ACS Applied Materials & Interfaces.

RuO₂ has drawn global attention as a possible “altermagnetic” material, a newly predicted class of materials that could enable faster, more energy-efficient computing technologies. The excitement has been fueled by theory and early experimental reports suggesting that RuO₂ might host an unusual magnetic state with major implications for spintronics and high-speed electronics.

“Altermagnets are a hot field of research right now,” said Steven Bennett, Ph.D., an NRL materials scientist and co-author of the study. “There’s been a rush to experimentally demonstrate what theorists predicted, because the impact on high-speed, energy-efficient computing could be significant.”

Quantum trembling: Why there are no truly flat molecules

Traditional chemistry textbooks present a tidy picture: Atoms in molecules occupy fixed positions, connected by rigid rods. A molecule such as formic acid (methanoic acid, HCOOH) is imagined as two-dimensional—flat as a sheet of paper. But quantum physics tells a different story. In reality, nature resists rigidity and forces even the simplest structures into the third dimension.

Researchers led by Professor Reinhard Dörner of the Institute for Nuclear Physics at Goethe University have now determined the precise spatial structure of the “flat” formic acid molecule using an X-ray beam from the PETRA III synchrotron radiation source at the DESY accelerator center in Hamburg. They collaborated with colleagues from the universities of Kassel, Marburg and Nevada, the Fritz Haber Institute, and the Max Planck Institute for Nuclear Physics. The study is published in Physical Review Letters.

To accomplish this, they made use of two effects that occur when X-ray radiation strikes a molecule. First, the radiation ejects several electrons from the molecule (photoelectric effect and Auger effect). As a result, the atoms become so highly charged that the molecule bursts apart in an explosion (Coulomb explosion). The scientists succeeded in measuring these processes sequentially, even though they take place within femtoseconds—millionths of a billionth of a second.

Webb maps the mysterious upper atmosphere of Uranus

For the first time, an international team of astronomers have mapped the vertical structure of Uranus’s upper atmosphere, uncovering how temperature and charged particles vary with height across the planet. Using Webb’s NIRSpec instrument, the team observed Uranus for nearly a full rotation, detecting the faint glow from molecules high above the clouds.

These unique data provide the most detailed portrait yet of where the planet’s auroras form, how they are influenced by its unusually tilted magnetic field, and how Uranus’s atmosphere has continued to cool over the past three decades. The results, published in Geophysical Research Letters, offer a new window into how ice-giant planets distribute energy in their upper layers.

Led by Paola Tiranti of Northumbria University in the United Kingdom, the study mapped out the temperature and density of ions in the atmosphere extending up to 5,000 kilometers above Uranus’s cloud tops, a region called the ionosphere where the atmosphere becomes ionized and interacts strongly with the planet’s magnetic field. The measurements show that temperatures peak between 3,000 and 4,000 kilometers, while ion densities reach their maximum around 1,000 kilometers, revealing clear longitudinal variations linked to the complex geometry of the magnetic field.

Could a recently reported high-energy neutrino event be explained by an exploding primordial black hole?

The KM3NeT collaboration is a large research group involved in the operation of a neutrino telescope network in the deep Mediterranean Sea, with the aim of detecting high-energy neutrino events. These are rare and fleeting high-energy interactions between neutrinos, particles with an extremely low mass that are sometimes referred to as “ghost particles.”

Recently, the KM3NeT collaboration reported an extremely high-energy neutrino event, which carried an energy of approximately 220 PeV (peta-electron volts). This is one of the most energetic events recorded to date and its cosmological origin has not yet been identified.

Researchers at Universidade de São Paulo and Universidad Autónoma de Madrid carried out a theoretical study exploring one proposed explanation for this remarkable neutrino event, namely that it originated from the explosion of a primordial black hole near Earth.

Quantum entanglement pushes optical clocks to new precision

By replacing single atoms with an entangled pair of ions, physicists in Germany have demonstrated unprecedented stability in an optical clock. Publishing their results in Physical Review Letters, a team led by Kai Dietze at the German National Metrology Institute, hope their approach could help usher in a new generation of optical clocks—opening up new possibilities in precision experiments and metrology.

To measure the passing of time, every clock works by counting oscillations of some reference frequency—whether it’s the swinging pendulum of a clocktower, or the vibrations of an electrified quartz crystal in a modern digital clock. Timekeeping accuracy is directly tied to how reliable these oscillations are: while a pendulum can accrue noticeable variations in its swing, vibrating quartz is far more reliable, making quartz clocks far more accurate.

Today, optical clocks are the most precise timekeepers ever achieved. In these devices, atoms are first “probed” by an ultra-stable laser tuned close to a specific optical transition. When the laser frequency matches the energy difference between two electronic states, an electron is excited to a higher energy level.

Lab-in-the-loop framework enables rapid evolution of complex multi-mutant proteins

The search space for protein engineering grows exponentially with complexity. A protein of just 100 amino acids has 20100 possible variants—more combinations than atoms in the observable universe. Traditional engineering methods might test hundreds of variants but limit exploration to narrow regions of the sequence space. Recent machine learning approaches enable broader searches through computational screening. However, these approaches still require tens of thousands of measurements, or 5–10 iterative rounds.

With the advent of these foundational protein models, the bottleneck for protein engineering swings back to the lab. For a single protein engineering campaign, researchers can only efficiently build and test hundreds of variants. What is the best way to choose those hundreds to most effectively uncover an evolved protein with substantially increased function? To address this problem, researchers have developed MULTI-evolve, a framework for efficient protein evolution that applies machine learning models trained on datasets of ~200 variants focused specifically on pairs of function-enhancing mutations.

Published in Science, this work represents Arc Institute’s first lab-in-the-loop framework for biological design, where computational prediction and experimental design are tightly integrated from the outset, reflecting a broader investment in AI-guided research.

Particles don’t always go with the flow (and why that matters)

It is commonly assumed that tiny particles just go with the flow as they make their way through soil, biological tissue, and other complex materials. But a team of Yale researchers led by Professor Amir Pahlavan shows that even gentle chemical gradients, such as a small change in salt concentration, can dramatically reshape how particles move through porous materials. Their results are published in Science Advances.

How small particles known as colloids, like fine clays, microbes, or engineered particles, move through porous materials such as soil, filters, and biological tissue can have significant and wide-ranging effects on everything from environmental cleanups to agriculture.

It’s long been known that chemical gradients—that is, gradual changes in the concentration of salt or other chemicals—can drive colloids to migrate directionally, a phenomenon known as diffusiophoresis. But it was often assumed that this effect would matter only when there was little or no flow, because phoretic speeds are typically orders of magnitude smaller than average flow speeds in porous media. Experiments set up in Pahlavan’s lab demonstrated a very different outcome.

Microscopic mirrors for future quantum networks: A new way to make high-performance optical resonators

Researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Faculty of Arts and Sciences have devised a new way to make some of the smallest, smoothest mirrors ever created for controlling single particles of light, known as photons. These mirrors could play key roles in future quantum computers, quantum networks, integrated lasers, environmental sensing equipment, and more.

A team from the labs of Marko Lončar, the Tiantsai Lin Professor of Electrical Engineering at SEAS; Mikhail Lukin, the Joshua and Beth Friedman University Professor in the Department of Physics; and Kiyoul Yang, assistant professor of electrical engineering at SEAS; have described their new method for making high-performance, curved optical mirrors in a study published in Optica.

Using two such mirrors to trap light between them, the team demonstrated state-of-the-art optical resonators that can control light at near-infrared wavelengths, which is important for manipulating single atoms in quantum computing applications.

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