Thermal lepton pairs are ideal probes for the temperature of quark-gluon plasma. Here, the STAR Collaboration uses thermal electron-positron pair production to measure quark-gluon plasma average temperature at different stages of the evolution.
Category: particle physics – Page 5
Climate intervention may lower protein content in major global food crops
A new study in Environmental Research Letters reports that cooling the planet by injecting sulfur dioxide into the stratosphere, a proposed climate intervention technique, could reduce the nutritional value of the world’s crops.
Scientists at Rutgers University used global climate and crop models to estimate how stratospheric aerosol intervention (SAI), one type of solar geoengineering, would impact the protein level of the world’s four major food crops: maize, rice, wheat, and soybeans. The SAI approach, inspired by volcanic eruptions, would involve releasing sulfur dioxide into the stratosphere. This gas would transform into sulfuric acid particles, forming a persistent cloud in the upper atmosphere that reflects a small part of the sun’s radiation, thereby cooling Earth.
While these cereal crops are primarily sources of carbohydrates, they also provide a substantial share of dietary protein for large portions of the global population. Model simulations suggested that increased CO2 concentrations tended to reduce the protein content of all four crops, while increased temperatures tended to increase the protein content of crops. Because SAI would stop temperatures from increasing, the CO2 effect would not be countered by warming, and protein would decrease relative to a warmer world without SAI.
Physicists Take the Imaginary Numbers Out of Quantum Mechanics
A century ago, the strange behavior of atoms and elementary particles led physicists to formulate a new theory of nature. That theory, quantum mechanics, found immediate success, proving its worth with accurate calculations of hydrogen’s emission and absorption of light. There was, however, a snag. The central equation of quantum mechanics featured the imaginary number i, the square root of −1.
Physicists knew i was a mathematical fiction. Real physical quantities like mass and momentum never yield a negative amount when squared. Yet this unreal number that behaves as i2 = −1 seemed to sit at the heart of the quantum world.
After deriving the i-riddled equation — essentially the law of motion for quantum entities — Erwin Schrödinger expressed the hope that it would be replaced by an entirely real version. (“There is undoubtedly a certain crudeness at the moment” in the equation’s form, he wrote in 1926.) Schrödinger’s distaste notwithstanding, i stuck around, and new generations of physicists took up his equation without much concern.
Spins influence solid oxygen’s crystal structure under extreme magnetic fields, study finds
Placing materials under extremely strong magnetic fields can give rise to unusual and fascinating physical phenomena or behavior. Specifically, studies show that under magnetic fields above 100 tesla (T), spins (i.e., intrinsic magnetic orientations of electrons) and atoms start forming new arrangements, promoting new phases of matter or stretching a crystal lattice.
One physical effect that can take place under these extreme conditions is known as magnetostriction. This effect essentially prompts a material’s crystal structure to stretch out, shrink or deform.
When magnetic fields above 100 T are produced experimentally, they can only be maintained for a very short time, typically for only a few microseconds. This is because their generation poses great stress on the wires used to produce the fields (i.e., coils), causing them to break almost immediately.
New holography-inspired reconfigurable surface developed for wireless communication
Reconfigurable intelligent surfaces (RIS) are engineered structures comprised of several elements known as ‘meta-atoms,’ which can reshape and control electromagnetic waves in real-time. These surfaces could contribute to the further advancement of wireless communications and localization systems, as they could be used to reliably redirect, strengthen and suppress signals.
In conventional applications of RIS for wireless communication, each meta-atom is controlled by a system known as the ‘base-station,’ which is connected to the surface via electrical cables. While surfaces following this design can attain good results, their reliance on wires and a base station could prevent or limit their real-world deployment.
Researchers at Tsinghua University and Southeast University recently developed a new RIS that controls itself and does not need to be connected to a base station. This new surface, introduced in a paper published in Nature Electronics, draws inspiration from holography, a well-known method to record and reconstruct an object’s light pattern to produce a 3D image of it.
Table salt enables new metallic nanotubes with potential for faster electronics
For the first time, researchers have made niobium sulfide metallic nanotubes with stable, predictable properties, a long-sought goal in advanced materials science. According to the international team, including a researcher at Penn State, that made the accomplishment, the new nanomaterial that could open the door to faster electronics, efficient electricity transport via superconductor wires and even future quantum computers was made possible with a surprising ingredient: table salt.
They published their research in ACS Nano.
Nanotubes are structures so small that thousands of them could fit across the width of a human hair. The tiny hollow cylinders are made by rolling up sheets of atoms; nanotubes have an unusual size and shape that can cause them to behave very differently from 3D, or bulk, materials.
Single organic molecule triggers Kondo effect in molecular-scale ‘Kondo box’
A research group led by Prof. Li Xiangyang from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, has made a new discovery: a single organic molecule can induce the Kondo effect in a magnetic atom, challenging the long-standing belief that this quantum phenomenon requires a vast sea of metallic electrons.
The research results were published in Physical Review Letters.
The Kondo effect is a quantum many-body phenomenon where conduction electrons in a metal collectively screen the magnetic moment of a localized impurity atom. It has been helping to explain strongly correlated electron behavior and inspiring advances in nanoscience, molecular electronics, and quantum information research.
Identical particles as a genuine non-local resource
npj Quantum Inf ormation volume 11, Article number: 171 (2025) Cite this article.
Quantum “Pinball” State of Matter: Electrons That Conduct and Insulate at the Same Time
Physicists at Florida State University (FSU) have uncovered a fascinating new phase of matter — a “ quantum pinball state” in which electrons act both as conductors and insulators at the same time. In this bizarre quantum regime, some electrons freeze into a rigid crystalline lattice while others move freely around them, much like balls ricocheting around fixed pins in a pinball machine. The discovery offers a new perspective on how quantum materials behave and could pave the way for breakthroughs in quantum computing, spintronics, and superconductivity.
The research, published in npj Quantum Materials, was led by Dr. Aman Kumar, Prof. Hitesh Changlani, and Prof. Cyprian Lewandowski of FSU’s National High Magnetic Field Laboratory. Their study explores how electrons in a two-dimensional “moiré lattice” can transition between solid-like and liquid-like states under certain conditions, forming what physicists call a generalized Wigner crystal.