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Category: physics – Page 129

Recently, a research team led by Prof. Guo Guangcan from the University of Science and Technology of China (USTC) constructed a non-Hermiticity (NH) synthetic orbital angular momentum (OAM) dimension in a degenerate optical cavity and observed the exceptional points (EPs). This study was published in Science Advances.

In topological physics, the NH systems depict open systems with complex spectra. Exceptional points are one of the unique features of NH systems. To study EPs, the team had constructed synthetic one-dimensional lattices and established topological simulation platform in a degenerate optical cavity. Based on this platform, an additional pseudomomentum was introduced as a parameter to construct the Dirac point in the two-dimensional momentum space. A pair of EPs can be obtained by introducing non-Hermitian perturbation around the Dirac point.

The detection of complex energy spectra in NH systems can be troublesome for traditional means. The research group developed a method which is referred to as wave front angle–resolved band structure spectroscopy to investigate complex energy spectra based on synthetic OAM. Using this method, the team not only detected EPs in momentum space, but also the key features of EPs like bulk Fermi arcs, parity-time symmetry-breaking transition, energy swapping and half-integer band windings.

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Simulations show that nonlinear spacetime dynamics manifest in the postmerger gravitational-wave signal of binary black hole coalescence.

“Spacetime tells matter how to move; matter tells spacetime how to curve.” This statement by physicist John Wheeler captures a defining feature of general relativity: its prediction of nonlinear spacetime dynamics. Such nonlinear evolution should be most evident in energetic spacetime events such as merging black holes, prompting the question of whether we can test for it using observations of gravitational waves emitted during such mergers. Two independent teams, led by Keefe Mitman at the California Institute of Technology [1] and Mark Ho-Yeuk Cheung at Johns Hopkins University in Maryland [2], show that this is the case. Using numerical simulations, they show the presence of nonlinearity in postmerger gravitational-wave signals.

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A pair of worlds that are just around the corner in cosmic terms look to be in the right spot to potentially host life as we know it.

A report in the February issue of the journal Astronomy and Astrophysics details the discovery of two exoplanets the orbit the red M-dwarf star GJ (or Gliese) 1002 in its habitable zone and are not far off from the mass of Earth.

These two characteristics top the list of things that make another planet worth getting excited about in terms of the odds it might have some sort of critters or even just primitive microorganisms hanging out.

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Dr. Tamar Gutnick, first author and former postdoctoral researcher in the Physics and Biology Unit at the Okinawa Institute of Science and Technology (OIST), said, “If we want to understand how the brain works, octopuses are the perfect animal to study as a comparison to mammals. They have a large brain, an amazingly unique body, and advanced cognitive abilities that have developed completely differently from those of vertebrates.”

“Octopuses have eight powerful and ultra-flexible arms, which can reach anywhere on their body. If we tried to attach wires to them, they would immediately rip it off, so we needed to get the equipment out of their reach by placing it under their skin.”

Scientists settled on small and lightweight data loggers as the solution, initially designed to track the brain activity of birds during flight. The team modified the devices to be waterproof and compact enough to slip inside the octopuses easily. Up to 12 hours of continuous recording were possible with the batteries, which had to operate in a low-air condition.

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