Lifeboat Foundation

Scientists have yet to obtain a complete microscopic understanding of how a supercooled liquid behaves as it turns into a glass. Different theories can capture different aspects of the spatial and temporal dynamics of this process, but the assumptions behind these theories are, in some cases, mutually exclusive. Now Yoshihiko Nishikawa at Tohoku University, Japan, and Ludovic Berthier at the University of Montpellier, France, reconcile two competing descriptions of this glass-transition behavior using a recently developed lattice model [1].

A prominent glass-transition theory known as random first-order transition theory holds that a cooling glass-forming liquid adopts a mosaic-like static structure with finite-range order. In this framework, so-called dynamic fluctuations—reorganizations of a material’s particles—occur when boundaries between mosaic “tiles” collectively rearrange. These fluctuations are fundamentally tied to static, region-to-region variations in a material’s structure. A competing theory known as dynamic-facilitation theory contains no assumptions about the system’s static structure or region-to-region variations. This theory postulates that dynamic fluctuations occur via local, small-scale particle rearrangements that trigger a reorganizational chain reaction that then propagates through the material.

For their study, Nishikawa and Berthier used a different theory to probe the glass transition of a supercooled liquid. Their three-dimensional lattice theory exhibits mosaic-like structural variations that are consistent with those from random first-order transition theory. However, the researchers found that the model’s predictions for the dynamic fluctuations more closely resemble those of the dynamic-facilitation framework. Nishikawa says that no current experiments can directly confirm the occurrence of these behaviors in real glass-forming materials. But he hopes to use the three-dimensional lattice model to reproduce some recently observed indirect experimental data.

Researchers have made a landmark discovery in quantum physics by observing and quantitatively characterizing the many-body pairing pseudogap in unitary Fermi gases, a topic of debate for nearly two decades. This finding not only resolves long-standing questions about the nature of the pseudogap in these gases but also suggests a potential link to the pseudogap observed in high-temperature superconductors. Credit: SciTechDaily.com.

Researchers have conclusively observed the many-body pairing pseudogap in unitary Fermi gases, advancing our understanding of superconductivity mechanisms.

A research team led by Professors Jianwei Pan, Xingcan Yao, and Yu’ao Chen from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, has for the first time observed and quantitatively characterized the many-body pairing pseudogap in unitary Fermi gases.

Launching rockets into space with atomic bombs is a crazy idea that was thankfully discarded many decades ago. But as Richard Corfield discovers, the potential of using the energy from nuclear-powered engines to drive space travel is back on NASA’s agenda.

In 1914 H G Wells published The World Set Free, a novel based on the notion that radium might one day power spaceships. Wells, who was familiar with the work of physicists such as Ernest Rutherford, knew that radium could produce heat and envisaged it being used to turn a turbine. The book might have been a work of fiction, but The World Set Free correctly foresaw the potential of what one might call “atomic spaceships”

The idea of using nuclear energy for space travel took hold in the 1950s when the public – having witnessed the horrors of Hiroshima and Nagasaki – gradually became convinced of the utility of nuclear power for peaceful purposes. Thanks to programmes such as America’s Atoms for Peace, people began to see that nuclear power could be used for energy and transport. But perhaps the most radical application lay in spaceflight.

Big plans at CERN! With a £12bn colossal atom-smasher on the drawing board, we’re one step closer to unlocking the cosmic secrets that surround us. Is this a worthy investment?

Explore the Future Circular Collider plans, a £12bn project. Will this supercollider be the key to unlocking the missing 95% of the universe?

It’s possible to start a subscale deployment in just a few years. The climate effects would be tiny, but the geopolitical impact could be significant.

Tokamak fusion plasmas benefit from high pressures but are then susceptible to modes of instability. These magnetohydrodynamic (MHD) modes are macroscopic distortions of the plasma, but certain collective motions of individual particles can provide stabilizing effects opposing them. The presence of a resistive wall slows the mode growth, converting a kink to a resistive wall mode (RWM). A kinetic MHD model includes Maxwell’s equations, ideal MHD constraints, and kinetic effects included through the pressure tensor, calculated with the perturbed drift-kinetic distribution function of the particles. The kinetic stabilizing effects on the RWM arise through resonances between the plasma rotation and particle drift motions: precession, bounce, and transit. A match between particle motions and the mode allows efficient transfer of energy that would otherwise drive the growth of the mode, thus damping the growth. The first approach to calculating RWM stability is to write a set of equations for the complex mode frequency in terms of known quantities and then to solve the system. The “energy principle” approach, which has the advantage of clarity in distinguishing the various stabilizing and destabilizing effects, is to change the force balance equation into an equation in terms of changes of kinetic and potential energies, and then to write a dispersion relation for the mode frequency in terms of those quantities. These methods have been used in various benchmarked codes to calculate kinetic effects on RWM stability. The theory has illuminated the important roles of plasma rotation, energetic particles, and collisions in RWM stability.

The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we use it as motivation for a broader review of the ways that baryon number violation, be it real or apparent, and dark sectors can intertwine and how neutron star observables, both present and future, can constrain them.

NASA’s Parker Solar Probe is crashing through a hailstorm of dust as it hurtles towards the sun at awe-inspiring speed.

The probe’s team members found that high-speed impacts with dust particles are not only more common than expected, they’re making tiny plumes of superhot plasma on the surface of the craft, according to an announcement for a new study.

The probe’s main mission goals are to measure the electric and magnetic fields near the sun and learn more about the solar wind—the stream of particles coming off of the sun, says David Malaspina, a space plasma physicist at the University of Colorado Boulder Astrophysical and Planetary Sciences Department and Laboratory for Atmospheric and Space Physics. Malaspina led the study, which the team will present at a conference this week.

DUNE, a neutrino research project, seeks to unravel the matter-antimatter imbalance mystery by tracking neutrino transformations.