After a successful commissioning run, GRETA is ready to give researchers an unprecedented look into the hearts of atoms.
Category: particle physics – Page 24
Trembling Photons in Non-Abelian Electric Fields
A ring of optical fiber can be made to host phenomena that originated in the realm of high-energy physics.
In non-Abelian gauge theories, particles interact with each other; operation order matters; and a so-called gauge symmetry ensures the invariance of physical laws under local transformations via fields mediated by photons, gluons, and the W and Z bosons. Such theories describe the strong and weak forces; provide the mathematical backbone of the standard model; and underpin efforts to understand the early Universe, quantum gravity, and exotic topological phases of matter. For decades, subjecting these theories to direct experimental scrutiny often meant resorting to enormous particle accelerators. Recently, an experimental approach known as photonic synthetic dimensions has offered a tabletop alternative. Applications of the approach have already realized a non-Abelian magnetic field [1]. Now Shu Yang of the University of Hong Kong and his colleagues have synthesized the corresponding non-Abelian electric field [2].
Water’s local asymmetry drives proton hopping between molecules, simulations reveal
Complex simulations—the most intricate of their kind to date—carried out by an international research team led by scientists at Heidelberg University’s Institute for Physical Chemistry, have revealed how water governs the way protons move through it. Using their modeling, researchers from Cambridge (U.K.), Bochum, Dijon (France) and Heidelberg were able to trace, in full quantum detail, the movements of a proton shared among six water molecules. At its core, the work addresses how a proton moves through water: not as a single particle drifting along, but by “hopping” from one molecule to the next.
This “hopping” motion has been known since the 19th century. When an acid dissolves in water, the released proton—a positively charged hydrogen ion—does not remain bound to a single water molecule. It is highly mobile and constantly jumps from one molecule to the next.
New thermodynamic framework explains pressure and edge currents in spinning active particles
Physicists from Heinrich Heine University Düsseldorf (HHU), the Technical University of Darmstadt, Sapienza University in Rome and the University of Camerino (both in Italy) have calculated the fundamental laws of thermodynamics for a gas composed of spinning particles. In the scientific journal Proceedings of the National Academy of Sciences (PNAS), they demonstrate that the pressure of this gas is similar to that of a normal gas but at an elevated temperature. In addition, localized surface currents arise that can be used for targeted particle transport.
The so-called ideal gas law is one of the fundamentals of thermodynamics and states that the pressure of a gas is proportional to its density and temperature. From a microscopic perspective, pressure is the average force per unit area exerted by incoming particles on impact and reflection. At a higher temperature, the particles move more quickly and therefore exert greater pressure on impact.
A research team led by Dr. Hartmut Löwen from the Institute for Theoretical Physics II at HHU asked whether the ideal gas law also applies to self-propelled, so-called “active” particles or whether the nonequilibrium state results in significant differences. In addition to the physicists in Düsseldorf, colleagues from Rome, Camerino and Darmstadt were also involved.
CarbonationEmpowered Offshore Deep Cement Mixing Enables Undredged Land
A new study in Communications Engineering reports a construction strategy that could change how offshore reclaimed land is stabilized—using carbonation to strengthen deep cement mixing from microscopic reactions to full in-situ performance.
Conventional deep cement mixing relies on mechanically blending cement and soil, but its long-term durability in waterlogged, newly dredged environments remains a challenge. The researchers propose mixing: a process that uses carbon dioxide to drive mineral formation within the cemented soil matrix, improving both strength and stability.
At the micro-scale, carbonation converts reactive components in the cement into carbonate minerals. This reaction can refine the pore structure, reduce permeability, and bind loose particles more effectively than ordinary curing alone. In practical terms, the cement-soil composite becomes less vulnerable to water ingress and chemical attack.
AI extracts hidden material rules from microscopic data to predict large-scale behavior
Researchers from the National University of Singapore (NUS) have developed artificial intelligence (AI) methods that learn the large-scale behavior of complex materials from microscopic data. By automatically identifying a small number of hidden variables that capture the collective behavior of a system, the methods can predict how materials evolve over time while reducing the need for costly simulations.
Understanding the behavior of materials at the macroscopic scale is essential for designing new technologies, from energy-efficient electronics to advanced alloys. However, material properties emerge from the interactions of vast numbers of atoms, and simulating every atom over long periods is often computationally impossible, even on modern supercomputers.
A major challenge in materials science is connecting these microscopic processes, such as atomic motion, to observable material properties. Existing approaches often require large-scale simulations that are prohibitively expensive.
Physicists say quantum mechanics may not need imaginary numbers after all
Physicists from Heinrich Heine University Düsseldorf (HHU) have examined a fundamental property of quantum mechanics in collaboration with the German Aerospace Center (DLR). In the scientific journal Physical Review Letters, they show that this theory does not necessarily need to be formulated with imaginary numbers – real numbers can in fact also be used.
Quantum mechanics is the branch of physics that explains how matter and energy behave at the atomic and subatomic scale. Developed in the early 1900s by pioneers including Max Planck, Niels Bohr, Werner Heisenberg, and Erwin Schrödinger, it has become one of the most successful scientific theories ever created.
The theory accurately describes a wide range of microscopic phenomena. These include the famous double slit experiment, in which particles also display wave like behavior, and quantum tunneling, where particles have a probability of passing through a barrier even when they do not have enough energy to overcome it in the classical sense. Other key quantum effects, such as entanglement and coherence, now form the foundation of emerging technologies including quantum computing and quantum communication.
When It Comes to Fusion, Materials Matter
In the experiment, researchers used two different methods to pack deuterium, a heavy form of hydrogen atoms that is often used in fusion, into thin foils of palladium and titanium. They then fired a beam of deuterium ions at the foils at different energies and measured how often fusion happened. Then they compared the rates from the different materials and methods with the “bare” fusion reaction (not in a material).
The team found that fusion rates depended on how the deuterium was loaded into the metal foils. The biggest effect was at the lowest energies, below 2.5 kiloelectronvolts (keV), where theory predicts fusion rates drop off sharply. Instead, researchers found a surprising plateau: Some samples showed elevated fusion rates roughly a quintillion times higher than bare fusion reactions. (A quintillion is a 1 followed by 18 zeroes.)
Researchers are not exactly sure why that’s happening, though they have some ideas and ways to test them. The electrons and defects within the material might partially shield repulsive electrostatic forces between deuterium nuclei, making it easier for them to get close together and fuse. Tuning the electronic structure, defects, and composition of materials could help make nuclear reactions happen more readily.