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Category: particle physics – Page 273

Researchers transform our understanding of crystals

When most people think of crystals, they picture suncatchers that act as rainbow prisms or the semi-transparent stones that some believe hold healing powers. However, to scientists and engineers, crystals are a form of materials in which their constituents—atoms, molecules, or nanoparticles—are arranged regularly in space. In other words, crystals are defined by the regular arrangement of their constituents. Common examples are diamonds, table salt, or sugar cubes.

However, in research just published in Soft Matter, a team led by Rensselaer Polytechnic Institute’s Sangwoo Lee, associate professor in the Department of Chemical and Biological Engineering, discovered that crystal structures are not necessarily always regularly arranged. The discovery advances the field of materials science and has unrealized implications for the materials used for semiconductors, solar panels, and electric vehicle technologies.

One of the most common and important classes of crystal structures is the close-packed structures of regular spheres constructed by stacking layers of spheres in a honeycomb arrangement. There are many ways to stack the layers to construct close-packed structures, and how nature selects specific stacking is an important question in materials and physics research. In the close-packing construction, there is a very unusual structure with irregularly spaced constituents known as the random stacking of two-dimensional hexagonal layers (RHCP). This structure was first observed from cobalt metal in 1942, but it has been regarded as a transitional and energetically unpreferred state.

Quantum matter breakthrough: Tuning density waves

Scientists at EPFL have found a new way to create a crystalline structure called a “density wave” in an atomic gas. The findings can help us better understand the behavior of quantum matter, one of the most complex problems in physics. The research was published May 24 in Nature.

“Cold atomic gases were well known in the past for the ability to ‘program’ the interactions between atoms,” says Professor Jean-Philippe Brantut at EPFL. “Our experiment doubles this ability.” Working with the group of Professor Helmut Ritsch at the University of Innsbruck, they have made a breakthrough that can impact not only quantum research but quantum-based technologies in the future.

Scientists have long been interested in understanding how materials self-organize into complex structures, such as crystals. In the often-arcane world of quantum physics, this sort of self-organization of particles is seen in “,” where particles arrange themselves into a regular, repeating pattern or order; like a group of people with different colored shirts on standing in a line but in a pattern where no two people with the same color shirt stand next to each other.

Curved-Laser Demonstration for a Higher-Energy Laser Accelerator

A curved “laser wakefield accelerator” could boost the acceleration potential of a multistage version of this device.

Laser wakefield accelerators (LWFAs) use laser-generated plasmas to accelerate electrons to high energies. The devices are significantly smaller than radio-frequency-based particle accelerators—centimeters versus hundreds of meters—making them less expensive, more efficient alternatives. But researchers still need to demonstrate that LWFAs can achieve particle energies that match those of their conventional counterparts. Now Xinzhe Zhu from Shanghai Jiao Tong University and colleagues have brought that goal a step closer, demonstrating a method for linking multiple LWFAs in a way that would boost their acceleration potential [1].

In an LWFA, charged particles reach relativistic speeds by surfing a wave of plasma created by a powerful laser. The particle energy achievable with a single LWFA is limited to a few GeV for two reasons: the particle bunch and the plasma wave quickly fall out of sync, and the laser energy dissipates with distance. Routing particles through multiple connected LWFAs would overcome these problems. But current techniques for combining LWFAs require refocusing the beam at each connection, lowering the efficiency of the process.

Higgs Boson: Our Passport to the Hidden Valley of New Physics in Next-Gen Particle Accelerators

It may be that the famous Higgs boson, co-responsible for the existence of masses of elementary particles, also interacts with the world of the new physics that has been sought for decades. If this were indeed to be the case, the Higgs should decay in a characteristic way, involving exotic particles. At the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow, it has been shown that if such decays do indeed occur, they will be observable in successors to the LHC currently being designed.

When talking about the ‘hidden valley’, our first thoughts are of dragons rather than sound science. However, in high-energy physics, this picturesque name is given to certain models that extend the set of currently known elementary particles. In these so-called Hidden Valley models, the particles of our world as described by the Standard Model belong to the low-energy group, while exotic particles are hidden in the high-energy region. Theoretical considerations suggest then the exotic decay of the famous Higgs boson, something that has not been observed at the LHC accelerator despite many years of searching. However, scientists at the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow argue that Higgs decays into exotic particles should already be perfectly observable in accelerators that are successors to the Large Hadron Collider – if the Hidden Valley models turn out to be consistent with reality.

“In Hidden Valley models we have two groups of particles separated by an energy barrier. The theory is that there could then be exotic massive particles that could cross this barrier under specific circumstances. The particles like Higgs boson or hypothetic Z’ boson would act as communicators between the particles of both worlds. The Higgs boson, one of the most massive particle of the Standard Model, is a very good candidate for such a communicator,” explains Prof. Marcin Kucharczyk (IFJ PAN), lead author of an article in the Journal of High Energy Physics, which presents the latest analyses and simulations concerning the possibility of detecting Higgs boson decays in the future lepton accelerators.

Bridging Quantum Theory and Relativity: Curved Spacetime in a Quantum Simulator

New techniques can answer questions that were previously inaccessible experimentally — including questions about the relationship between quantum mechanics and relativity.

Scientists at TU Wien and other institutions have developed a “quantum simulator” using ultracold atomic clouds to model quantum particles in curved spacetime, marking a major step toward reconciling quantum theory and the theory of relativity. The model system offers a tool to study gravitational lensing effects in a quantum field, which may lead to new insights in the elusive field of quantum gravity and other areas of physics.

The theory of relativity works well when you want to explain cosmic-scale phenomena — such as the gravitational waves.

Hello, Computer — Sabine Hossenfelder — A.I. going mainstream

Perspective from a very-educated layman. Er, laywoman.

This is Hello, Computer, a series of interviews carried out in 2023 at a time when artificial intelligence appears to be going everywhere, all at once.

Sabine Hossenfelder is a German theoretical physicist, science communicator, author, musician, and YouTuber. She is the author of Lost in Math: How beauty leads physics astray, which explores the concept of elegance in fundamental physics and cosmology, and of Existential Physics: A scientist’s guide to life’s biggest questions.

Sabine has published more than 80 research papers in the foundations of physics, from cosmology to quantum foundations and particle physics. Her writing has appeared in Scientific American, Nautilus, The New York Times, and The Guardian.

Sabine also works as a freelance popular science writer and runs the YouTube channel Science Without the Gobbledygook, where she talks about recent scientific developments and debunks hype, and a separate YouTube channel for music she writes and records.

Continue reading “Hello, Computer — Sabine Hossenfelder — A.I. going mainstream” | >

Physics: The big questions of our existence in under an hour

SABINE HOSSENFELDER: My name is Sabine Hossenfelder. I’m a physicist and Research Fellow at the Frankfurt Institute for Advanced Studies, and I have a book that’s called “Existential Physics: A Scientist’s Guide to Life’s Biggest Questions.”

NARRATOR: Why did you pursue a career in physics?

HOSSENFELDER: I originally studied mathematics, not physics, because I was broadly interested in the question how much can we describe about nature with mathematics? But mathematics is a really big field and I couldn’t make up my mind exactly what to study. And so I decided to focus on that part of mathematics that’s actually good to describe nature and that naturally led me to physics. I was generally trying to make sense of the world and I thought that human interactions, social systems are a pretty hopeless case. There’s no way I’ll ever make sense of them. But simple things like particles or maybe planets and moons, I might be able to work that out. In the foundations of physics, we work with a lot of mathematics and I know from my own experience that it’s really, really hard to learn. And so I think for a lot of people out there, the journal articles that we write in the foundations of physics are just incomprehensible.

Physics Breakthrough: First-Ever Measurement of a Quantum Paradox

How do quantum particles exchange information? An intriguing hypothesis regarding quantum information has recently been validated through experimental verification conducted at TU Wien.

If you were to randomly pick an individual from a crowd who stands remarkably taller than the average, it’s quite likely that this person will also surpass the average weight. This is because, statistically, knowledge about one variable often gives us some insight into another.

Quantum physics takes these correlations to another level, establishing even more potent connections between disparate quantities: distinct particles or segments of a vast quantum system can “share” a specific amount of information. This intriguing theoretical premise suggests that the calculation of this “mutual information” is surprisingly not influenced by the system’s overall volume, but only by its surface.