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Making Sense of Handedness on a Lattice

David Kaplan has developed a lattice model for particles that are left-or right-handed, offering a firmer foundation for the theory of weak interactions.

David Kaplan is on a quest to straighten out chirality, or “handedness,” in particle physics. A theorist at the University of Washington, Seattle, Kaplan has been wrestling with chirality conundrums for over 30 years. The main problem he has been working on is how to place chiral particles, such as left-handed electrons or right-handed antineutrinos, on a discrete space-time, or “lattice.” That may sound like a minor concern, but without a solution to this problem the weak interaction—and by extension the standard model of particle physics—can’t be simulated on a computer beyond low-energy approximations. Attempts to develop a lattice theory for chiral particles have run into model-dooming inconsistencies. There’s even a well-known theorem that says the whole endeavor should be impossible.

Kaplan is unfazed. He has been a pioneer in formulating chirality’s place in particle physics. One of his main contributions has been to show that some of chirality’s problems can be solved in extra dimensions. Kaplan has now taken this extra-dimension strategy further, showing that reducing the boundaries, or edges, around the extra dimensions can help keep left-and right-handed particle states from mixing [1, 2]. With further work, he believes this breakthrough could finally make the lattice “safe” for chiral particles. Physics Magazine spoke to Kaplan about the issues surrounding chirality in particle physics.

A Counterintuitive Set of Tunneling Effects Observed at Last

Graphene is the setting for the first demonstration of relativistic electrons’ paradoxical ability to whiz through a barrier, provided the barrier is high enough.

If an electron in a material has a speed that is independent of its energy and if it encounters a barrier head on, it can tunnel straight through. Derived by theorist Oskar Klein in 1929, this counterintuitive finding remained little tested in the lab because it is hard to make electrons approach a barrier head on and to stop them scattering off the edges of the sample. Now Mirza Elahi of the University of Virginia and his collaborators have observed evidence of Klein tunneling in monolayer graphene. What’s more, they also observed the opposite effect, anti-Klein tunneling, in bilayer graphene. In anti-Klein tunneling, head-on electrons do not tunnel at all, while others approaching the barrier at an intermediate angle do [1].

Graphene’s hexagonal lattice can be thought of as two identical interpenetrating triangular sublattices. One consequence of that view is that graphene’s charge carriers—electrons that hop between the two sublattices—behave as if massless and relativistic at low energies. Another consequence is that the two sublattices bestow on the electrons a chiral property, pseudospin, that resembles spin, which controls the nature of the transmission across the barrier.

Study reveals that the brain’s cerebellum can shape cognition

If you reward a monkey with some juice, it will learn which hand to move in response to a specific visual cue—but only if the cerebellum is functioning properly. So say neuroscientists at the University of Pittsburgh School of Medicine and Columbia University, who recently published findings in Nature Communications that show the brain region plays a crucial role in reward-based learning.

New focused approach can help untangle messy quantum scrambling problems

The world is a cluttered, noisy place, and the ability to effectively focus is a valuable skill. For example, at a bustling party, the clatter of cutlery, the conversations, the music, the scratching of your shirt tag and almost everything else must fade into the background for you to focus on finding familiar faces or giving the person next to you your undivided attention.

Advancements in Deep Ultraviolet Laser Technology

Researchers developed a 60-milliwatt solid-state DUV laser at 193 nm using LBO crystals, setting new benchmarks in efficiency values.

In the realm of science and technology, harnessing coherent light sources in the deep ultraviolet (DUV) region holds immense significance across various applications such as lithography, defect inspection, metrology, and spectroscopy. Traditionally, high-power 193-nanometer (nm) lasers have been pivotal in lithography, forming an integral part of systems used for precise patterning. However, the coherence limitations associated with conventional ArF excimer lasers hinder their effectiveness in applications requiring high-resolution patterns, like interference lithography.

Hybrid ArF Excimer Laser Technology

Unlocking the Secrets of Strength Through 3D Crack Analysis

The last time you dropped a favorite mug or sat on your glasses, you may have been too preoccupied to take much notice of the intricate pattern of cracks that appeared in the broken object. But capturing the formation of such patterns is the specialty of John Kolinski and his team at the Laboratory of Engineering Mechanics of Soft Interfaces (EMSI) in EPFL’s School of Engineering. They aim to understand how cracks propagate in brittle solids, which is essential for developing and testing safe and cost-effective composite materials for use in construction, sports, and aerospace engineering.

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