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Category: physics – Page 92

A strange pair of galaxies several billion light-years away could be evidence of a hypothetical ‘crease’ in the Universe’s fabric known as a cosmic string.

According to an analysis of the properties of the pair, the two galaxies may not be distinct objects, but a duplicate image caused by a trick of the light. And the reason the light is duplicated could be because of a scar in the space between us and the galaxy, creating a gravitational lens.

A paper describing this cosmic string candidate, led by Margarita Safonova of the Indian Institute of Astrophysics, has been accepted in the Bulletin de la Société Royale des Sciences de Liège, and is available on preprint server arXiv.

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For those still holding out hope that antimatter levitates rather than falls in a gravitational field, like normal matter, the results of a new experiment are a dose of cold reality.

Physicists studying antihydrogen—an anti-proton paired with an antielectron, or positron—have conclusively shown that gravity pulls it downward and does not push it upward.

At least for antimatter, antigravity doesn’t exist.

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Every so often, astronomers glimpse an intense flash of radio waves from space—a flash that lasts only instants but puts out as much energy in a millisecond as the sun does in a few years. The origin of these “fast radio bursts” is one of the greatest mysteries in astronomy today.

There is no shortage of ideas to explain the cause of the bursts: a catalog of current theories shows more than 50 potential scenarios. You can take your pick from highly magnetized , collisions of incredibly dense stars or many more extreme or exotic phenomena.

How can we figure out which theory is correct? One way is to look for more information about the bursts, using other channels: specifically, using ripples in the fabric of the universe called .

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The study’s authors compared the influence of two components of the brain’s physical structure: the outer folds of the cerebral cortex — the area where most higher-level brain activity occurs — and the connectome, the web of nerves that links distinct regions of the cerebral cortex. The team found that the shape of the outer surface was a better predictor of brainwave data than was the connectome, contrary to the paradigm that the connectome has the dominant role in driving brain activity. “We use concepts from physics and engineering to study how anatomy determines function,” says study co-author James Pang, a physicist at Monash University in Melbourne, Australia.

A model of the brain’s geometry better explains neuronal activity than a model based on the ‘connectome’.

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Imagine a juggler tossing balls into the air. The art of juggling is a dance between motion and pause, where the ball’s speed slows as it ascends, and then quickens on the way down. This dance reveals one of the core tenets of physics: conservation laws.

Simply put, these laws tell us that certain features of our world, like energy, don’t just vanish; they transform from one form to another. In our juggling example, the energy of motion (kinetic energy) morphs into the energy of position (potential energy) and back again.

Conservation laws aren’t just limited to juggling, or even Earth for that matter. They’re universal principles, true across various fields of physics. Yet, they aren’t always straightforward.

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The results of the Chi-Nu physics experiment at Los Alamos National Laboratory have contributed essential, never-before-observed data for enhancing nuclear security applications, understanding criticality safety and designing fast-neutron energy reactors. The Chi-Nu project, a years-long experiment measuring the energy spectrum of neutrons emitted from neutron-induced fission, recently concluded the most detailed and extensive uncertainty analysis of the three major actinide elements—uranium-238, uranium-235 and plutonium-239.

“Nuclear and related nuclear chain reactions were only discovered a little more than 80 years ago, and experimenters are still working to provide the full picture of fission processes for the major actinides,” said Keegan Kelly, a physicist at Los Alamos National Laboratory. “Throughout the course of this project, we have observed clear signatures of fission processes that in many cases were never observed in any previous experiment.”

The Los Alamos team’s final Chi-Nu study, on the isotope uranium-238, was recently published in Physical Review C. The experiment measured uranium-238’s prompt fission spectrum: the energy of the neutron inducing the fission—the neutron that crashes into a nucleus and splits it—and the potentially wide-ranging energy distribution (the spectrum) of the neutrons released as a result. Chi-Nu focuses on “fast-neutron-induced” fission, with incident neutron energies in millions of electron volts, where there have typically been very few measurements.

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In this episode, we explore how a triple-lens supernova observed by the James Webb Space Telescope could help solve the mystery of the Hubble tension, which is the discrepancy between different measurements of the expansion rate of the Universe. We also learn about the details of the supernova and the galaxy cluster that caused the gravitational lensing effect, and how JWST and other telescopes can use this supernova to test various cosmological models and parameters.

Paper Link:
https://arxiv.org/abs/2309.

Chapters:
00:00 Introduction.
01:10 How JWST Discovered a Rare and Triple-Lens Supernova.
04:13 How H0pe Can Measure the Expansion Rate in a New Way.
09:00 How hOpe can test various cosmological models.
11:26 Outro.
12:24 Enjoy.

Best Telescopes for beginners:

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