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Category: physics

Old galaxies in a young universe?

The standard cosmological model (present-day version of “Big Bang,” called Lambda-CDM) gives an age of the universe close to 13.8 billion years and much younger when we explore the universe at high-redshift. The redshift of galaxies is produced by the expansion of the universe, which causes emitted wavelengths to lengthen and move toward the red end of the electromagnetic spectrum.

The further away a galaxy is, the more rapidly it is moving with respect to us, and so the greater is its redshift; and, given that the speed of light is finite, the more we travel to the past. Hence, measuring the age of very high redshift galaxies would be a way to test the cosmological model. Galaxies cannot be older than the age of the universe in which they are; it would be absurd, like a son older than his mother.

In work carried out with my colleague, Carlos M. Gutiérrez, at the Canary Islands Astrophysics Institute (IAC; Spain), we analyzed 31 galaxies with average redshift 7.3 (when the universe was 700 Myr old, according to the standard model) observed with the most powerful available telescope available: the James Webb Space Telescope (JWST).

How charges invert a long-standing empirical law in glass physics

If you’ve ever watched a glass blower at work, you’ve seen a material behaving in a very special way. As it cools, the viscosity of molten glass increases steadily but gradually, allowing it to be shaped without a mold. Physicists call this behavior a strong glass transition, and silica glass is the textbook example. Most polymer glasses behave very differently, and are known as fragile glass formers. Their viscosity rises much more steeply as temperature drops, and therefore they cannot be processed without a mold or very precise temperature control.

There are other interesting differences between different glass formers. Most glasses exhibit relaxation behavior that deviates strongly from a single-exponential decay; this means that their relaxation is characterized by a broad spectrum of relaxation times, and is often associated with dynamic heterogeneities or cooperative rearrangements.

A long-standing empirical rule links the breadth of the relaxation spectrum to the fragility of the glass: strong glass formers such as silica tend to have a narrow relaxation spectrum, while fragile glass formers such as polymers have a much broader relaxation spectrum.

Third exoplanet detected in the planetary system HD 176986

Using HARPS and HARPS-N spectrographs, astronomers have observed a nearby K-type star designated HD 176986, known to host two super-Earth exoplanets. The observations resulted in the discovery of another planet in the system at least several times more massive than Earth. The finding was detailed in a paper published January 28 in the Astronomy & Astrophysics journal.

Seeing the whole from a part: Revealing hidden turbulent structures from limited observations and equations

The irregular, swirling motion of fluids we call turbulence can be found everywhere, from stirring in a teacup to currents in the planetary atmosphere. This phenomenon is governed by the Navier-Stokes equations—a set of mathematical equations that describe how fluids move.

Despite being known for nearly two centuries, these equations still pose major challenges when it comes to making predictions. Turbulent flows are inherently chaotic, and tiny uncertainties can grow quickly over time.

In real-world situations, scientists can only observe part of a turbulent flow, usually its largest and slowest moving features. Thus, a long-standing question in fluid physics has been whether these partial observations are enough to reconstruct the full motion of the fluid.

Physicists clarify key mechanism behind energy release in molybdenum-93

A team of physicists from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences, together with collaborators, has identified the dominant physical mechanism responsible for energy release in the nuclear isomer molybdenum-93m (Mo-93m). Using high-precision experiments, the researchers showed that inelastic nuclear scattering—rather than the long-hypothesized nuclear excitation by electron capture (NEEC)—is the primary driver of isomer depletion under their experimental conditions.

The findings, published in Physical Review Letters on February 6, provide crucial experimental evidence concerning a long-debated process and shed new light on the controlled release of nuclear energy.

How fast can a microlaser switch ‘modes?’ A simple rule reveals a power-law time scaling

Modern technologies increasingly rely on light sources that can be reconfigured on demand. Think of microlasers that can quickly switch between different operating states—much like a car shifting gears—so that an optical chip can route signals, perform computations, or adapt to changing conditions in real time. The microlaser switching is not a smooth, leisurely process, but can be sudden and fast. Generally, nearly identical “candidate” lasing states compete with each other in a microcavity, and the laser may abruptly jump from one state to another when external conditions are tuned.

This raises a practical question: How fast can such a switch be, in principle? For physicists, it raises a deeper one: Does the switching follow a universal rule, like other phase transitions in nature?

A team at Peking University has now provided a clear picture of an ultrahigh-quality microcavity laser—the time the laser needs to complete a state switch follows a remarkably simple power-law rule. When the control knob is swept faster, the switch becomes faster—but not arbitrarily so. Instead, the switching time decreases with the square root of the sweep speed, corresponding to a robust exponent close to half. This result effectively sets a speed limit for how quickly such microlasers can “change gears.” The findings are published in Physical Review Letters.

Understanding the physics at the anode of sodium-ion batteries

Sodium-ion batteries (NIBs) are gaining traction as a next-generation technology to complement the widely used lithium-ion batteries (LIBs). NIBs offer clear advantages versus LIBs in terms of sustainability and cost, as they rely on sodium—an element that, unlike lithium, is abundant almost everywhere on Earth. However, for NIBs to achieve widespread adoption, they must reach energy densities comparable to LIBs.

State-of-the-art NIB designs use hard carbon (HC), a porous and amorphous type of carbon, as an anode material. Scientists believe that sodium ions aggregate into tiny quasi-metallic clusters within HC nano-pores, and this “pore filling” process remains as the main mechanism contributing to the extended reversible capacity of the HC anode.

Despite some computational studies on this topic, the fundamental processes governing sodium storage and transport in HC remain unclear. Specifically, researchers have struggled to explain how sodium ions can gather to form clusters inside HC pores at operational temperatures, and why the overall movement of sodium ions through the material is sluggish.

Scientists show how to narrow the hunt for merging giant black holes

A new detection framework explains how astronomers can isolate extremely slow gravitational wave signals.

By combining subtle distortions in spacetime with observations of unusually bright galactic centers, the study authors have demonstrated a practical method for identifying likely locations of merging supermassive black holes.

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