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Category: physics

Nearby pulsar offers insights into emission physics near the death line

Using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), astronomers from the Chinese Academy of Sciences (CAS) and elsewhere have observed a nearby pulsar known as PSR J2129+4119. Results of the observational campaign, published October 30 on the arXiv pre-print server, deliver important insights into the behavior and properties of this pulsar.

Radio emission from pulsars exhibits a variety of phenomena, including subpulse drifting, nulling, or mode changing. In the case of subpulse drifting, radio emission from a pulsar appears to drift in spin phase within the main pulse profile. When it comes to nulling, the emission from a pulsar ceases abruptly from a few to hundreds of pulse periods before it is restored.

Discovered in 2017, PSR J2129+4119 is an old and nearby pulsar located some 7,500 light years away. It has a pulse period of 1.69 seconds, dispersion measure of 31 cm/pc3, and characteristic age of 342.8 million years. The pulsar lies below the so-called “death line”—a theoretical boundary in the period-period derivative diagram below which the coherent radio emission is sustained.

Chasing and splashing molecules create resilient order from apparent chaos, study shows

In nature, ordered structures are essential to maintain both stability and functionality in living systems, as observed in repeating structures or the formation of complex molecules. Yet, the creation of this order is based on universal physical principles which eventually allow the creation of living matter and organic structures.

One of these principles is non-reciprocal interactions: one type of molecule is attracted by another which, on the contrary, is repelled. This phenomenon can give rise to interesting structures and .

Scientists from the department of Living Matter Physics at MPI-DS have now discovered that non-reciprocal interactions can also induce stable collective movement in living systems. The study is published in the journal Physical Review Letters.

What Is a Manifold?

Standing in the middle of a field, we can easily forget that we live on a round planet. We’re so small in comparison to the Earth that from our point of view, it looks flat.

The world is full of such shapes — ones that look flat to an ant living on them, even though they might have a more complicated global structure. Mathematicians call these shapes manifolds. Introduced by Bernhard Riemann in the mid-19th century, manifolds transformed how mathematicians think about space. It was no longer just a physical setting for other mathematical objects, but rather an abstract, well-defined object worth studying in its own right.

This new perspective allowed mathematicians to rigorously explore higher-dimensional spaces — leading to the birth of modern topology, a field dedicated to the study of mathematical spaces like manifolds. Manifolds have also come to occupy a central role in fields such as geometry, dynamical systems, data analysis and physics.

Mindscape 334 | Daniel Whiteson on the Physics of and by Aliens

Patreon: https://www.patreon.com/seanmcarroll.
Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2025/11/03/334-…by-aliens/

The universe as revealed by physics is objective: it’s out there, existing and behaving in ways that are completely independent of human thought. But the process by which we learn about the universe, and the language with which we talk about it, is extremely human-dependent. Does that mean that aliens would do science differently, and even think differently about physics, even if we all live in the same universe? Physicist Daniel Whiteson has teamed with cartoonist Andy Warner to investigate these questions in their new book Do Aliens Speak Physics?

Daniel Whiteson received his Ph.D. in physics from the University of California at Berkeley. He is currently a professor of physics at the University of California, Irvine. He is a Fellow of the American Physical Society and recipient of an Emmy nomination. He is the author of several books, often with co-author Jorge Cham. He is the co-host (with Kelly Weinersmith) of the podcast Daniel and Kelly’s Extraordinary Universe.

Mindscape Podcast playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxY_fRExpDXr87tzRbPCaA5x.
Sean Carroll channel: https://www.youtube.com/c/seancarroll.

#podcast #ideas #science #philosophy #culture

Strong magnetic field helps answer a question about the ‘new duality’ in materials physics

As someone who studies materials, Lu Li knows people want to hear about the exciting new applications and technologies his discoveries could enable. Sometimes, though, what he finds is just too weird or extreme to have any immediate use.

Working with an international team of researchers, Li has made one of those latter types of discoveries, detailed in Physical Review Letters.

“I would love to claim that there’s a great application, but my work keeps pushing that dream further away,” said Li, professor of physics at the University of Michigan. “But what we’ve found is still really bizarre and exciting.”

Unit-free theorem pinpoints key variables for AI and physics models

Machine learning models are designed to take in data, to find patterns or relationships within those data, and to use what they have learned to make predictions or to create new content. The quality of those outputs depends not only on the details of a model’s inner workings but also, crucially, on the information that is fed into the model.

Some models follow a brute force approach, essentially adding every bit of data related to a particular problem into the model and seeing what comes out. But a sleeker, less energy-hungry way to approach a problem is to determine which variables are vital to the outcome and only provide the model with information about those key variables.

Now, Adrián Lozano-Durán, an associate professor of aerospace at Caltech and a visiting professor at MIT, and MIT graduate student Yuan Yuan, have developed a theorem that takes any number of possible variables and whittles them down, leaving only those that are most important. In the process, the model removes all units, such as meters and feet, from the underlying equations, making them dimensionless, something scientists require of equations that describe the physical world. The work can be applied not only to machine learning but to any .

What If Einstein Was Only Half Right? NASA’s New Test for Dark Energy

New strategies may soon allow scientists to test dark energy theories within our own solar system, linking cosmic-scale physics to local observation. Science advances through a cycle of proposing theories and rigorously testing them in search of contradictions. This process is especially challeng

Gravitational wave events hint at ‘second-generation’ black holes

In a paper published in The Astrophysical Journal Letters, the international LIGO-Virgo-KAGRA Collaboration reports on the detection of two gravitational wave events in October and November of 2024 with unusual black hole spins. This observation adds an important new piece to our understanding of the most elusive phenomena in the universe.

Gravitational waves are “ripples” in that result from cataclysmic events in deep space, with the strongest waves produced by the collision of black holes.

Using sophisticated algorithmic techniques and mathematical models, researchers are able to reconstruct many physical features of the detected black holes from the analysis of gravitational signals, such as their masses and the distance of the event from Earth, and even the speed and direction of their rotation around their axis, called spin.

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