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The release of Transformers has marked a significant advancement in the field of Artificial Intelligence (AI) and neural network topologies. Understanding the workings of these complex neural network architectures requires an understanding of transformers. What distinguishes transformers from conventional architectures is the concept of self-attention, which describes a transformer model’s capacity to focus on distinct segments of the input sequence during prediction. Self-attention greatly enhances the performance of transformers in real-world applications, including computer vision and Natural Language Processing (NLP).

In a recent study, researchers have provided a mathematical model that can be used to perceive Transformers as particle systems in interaction. The mathematical framework offers a methodical way to analyze Transformers’ internal operations. In an interacting particle system, the behavior of the individual particles influences that of the other parts, resulting in a complex network of interconnected systems.

The study explores the finding that Transformers can be thought of as flow maps on the space of probability measures. In this sense, transformers generate a mean-field interacting particle system in which every particle, called a token, follows the vector field flow defined by the empirical measure of all particles. The continuity equation governs the evolution of the empirical measure, and the long-term behavior of this system, which is typified by particle clustering, becomes an object of study.

In its ground state, the helium-8 (⁸He) nucleus consists of an alpha particle (⁴He nucleus) and four neutrons. If, before its few-hundred-milliseconds life ends, an ⁸ He nucleus is nudged into its first 0⁺ excited state, the four neutrons form two pairs known as dineutron clusters. According to theory, the alpha particle and the two neutron clusters settle into a three-member nuclear analog of a Bose-Einstein condensate. That outcome has now been observed for the first time by Zaihong Yang of Peking University and his colleagues at the RIKEN Nishina Center in Japan [1].

The experiment entailed firing a high-intensity beam of ⁸ He nuclei at polyethylene and carbon targets. Some collisions excited the nuclei into the sought-after condensate state, which promptly broke up into a helium-6 (⁶He) nucleus and a single neutron pair. The ⁶ He nuclei made their way through dipole magnets to drift detectors and plastic scintillators for characterization. The neutrons struck a plastic scintillator whose layered construction made it possible to identify which neutrons were correlated—that is, members of a dineutron cluster—and which were not. The correlated neutron pairs and the scattering count rate’s dependence on energy, angle, and type of target were all consistent with theoretical predictions of the nature of the correlated ⁸ He excited state.

The ⁸ He condensate resembles the so-called Hoyle state of carbon-12, which consists of three alpha particles in the condensed state. Astronomer Fred Hoyle predicted the state in 1954 to account for the synthesis of carbon in helium-burning stars. Yang points out that nuclear condensates could also have implications for understanding the structures of exotic nuclei and neutron stars.

Purdue quantum researchers twist double bilayers of an antiferromagnet to demonstrate tunable moiré magnetism.

Twistronics isn’t a new dance move, exercise equipment, or new music fad. No, it’s much cooler than any of that. It is an exciting new development in quantum physics and material science where van der Waals materials are stacked on top of each other in layers, like sheets of paper in a ream that can easily twist and rotate while remaining flat, and quantum physicists have used these stacks to discover intriguing quantum phenomena.

Adding the concept of quantum spin with twisted double bilayers of an antiferromagnet, it is possible to have tunable moiré magnetism. This suggests a new class of material platform for the next step in twistronics: spintronics. This new science could lead to promising memory and spin-logic devices, opening the world of physics up to a whole new avenue with spintronic applications.

Bluvstein, D., Evered, S.J., Geim, A.A. et al. Logical quantum processor based on reconfigurable atom arrays. Nature (2023). https://doi.org/10.1038/s41586-023-06927-3

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In a typical battery, charged ions zip one way through a sea of other particles as the battery recharges, before racing back in the other direction to release the stored energy on cue.

Back and forth the ions go, some getting diverted along the way, until the capacity of the battery is drained, and it loses energy too quickly to be of any use.

But physicists, good on them, are imagining new ways of storing energy in handy portable devices by drawing on a strange quantum phenomenon that twists time, amongst other unusual happenings.

The combined analysis of present and upcoming atmospheric-neutrino experiments may lead to the solution of outstanding puzzles in neutrino physics.

Neutrinos are fickle. Produced with a certain leptonic flavor (electron, muon, or tau), neutrinos can change their flavor as they travel through space. In 1998, researchers discovered this beyond-standard-model neutrino-oscillation phenomenon using neutrinos from natural sources—Earth’s atmosphere and the Sun. Increasingly accurate experiments also involved artificial neutrino sources such as accelerators and nuclear reactors. These experiments have significantly advanced our understanding of neutrino oscillations but haven’t yet solved two important related questions regarding the ordering of neutrino masses and possible violations by neutrinos of a fundamental symmetry known as charge-parity (CP) symmetry. New work by Carlos Alberto Argüelles-Delgado of Harvard University and colleagues shows that atmospheric neutrino experiments, once pivotal in the discovery of neutrino oscillation, can still play a key role in answering those questions [1].

The National Institute for Materials Science (NIMS) has succeeded in directly observing the “anisotropic magneto-Thomson effect,” a phenomenon in which the heat absorption/release proportional to an applied temperature difference and charge current (i.e., Thomson effect) changes anisotropically depending on the magnetization direction in magnetic materials.

This research is expected to lead to further development of basic physics and materials science related to the fusion area of thermoelectrics and spintronics, as well as to the development of new functionalities to control thermal energy with magnetism. The study is published in the journal Physical Review Letters.

The Thomson effect has long been known as one of the fundamental thermoelectric effects in metals and semiconductors, along with the Seebeck and Peltier effects, which are driving principles of thermoelectric conversion technologies.

String theory found its origins in an attempt to understand the nascent experiments revealing the strong nuclear force. Eventually another theory, one based on particles called quarks and force carriers called gluons, would supplant it, but in the deep mathematical bones of the young string theory physicists would find curious structures, half-glimpsed ghosts, that would point to something more. Something deeper.

String theory claims that what we call particles —the point-like entities that wander freely, interact, and bind together to make up the bulk of material existence—are nothing but. Instead, there is but a single kind of fundamental object: the string. These strings, each one existing at the smallest possible limit of existence itself, vibrate. And the way those strings vibrate dictates how they manifest themselves in the larger universe. Like notes on a strummed guitar, a string vibrating with one mode will appear to us as an electron, while another vibrating at a different frequency will appear as a photon, and so on.

String theory is an audacious attempt at a theory of everything. A single mathematical framework that explains the particles that make us who and what we are along with the forces that act as the fundamental messengers among those particles. They are all, every quark in the cosmos and every photon in the field, bits of vibrating strings.

For decades, achieving controlled fusion was a physics challenge. But now, as the ITER megaproject gears up to demonstrate fusion’s potential as an energy source—and startup companies race to beat it—the practical roadblocks to fusion power plants are coming into focus. One is a looming shortage of tritium fuel. Others could prevent reactors from ever running reliably—a necessity if fusion is to provide a constant “baseload” to complement intermittent solar and wind power.

Some of fusion’s fitfulness is innate to the design of doughnut-shaped tokamak reactors. The magnetic field that confines the ultrahot, energy-producing plasma is generated in part by the charged particles themselves, as they flow around the vessel. That plasma current in turn is induced by pulses of electrical current in a coil of wire in the doughnut’s hole, each lasting a few minutes at most. In between pulses the magnetic field ebbs, interrupting tokamak operations—and power delivery. The repetitive starts and stops of the reactor’s powerful magnetic fields also generate mechanical stresses that could eventually tear the machine apart.

In theory, the beams of particles and microwaves used to heat the plasma can also drive the plasma current. So can a quirk of plasma physics called the bootstrap effect. Near the edge of the plasma, a sharp pressure gradient causes the particles to spiral in such a way that they interfere with each other and push themselves—by their own bootstraps—around the ring.