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Category: physics

Astrophysicists test a new piece of the sky to probe dark matter and dark energy

In the leading model of cosmology, most of the universe is invisible: a combined 95% is made of dark matter and dark energy. Exactly what these dark components are remains a mystery, but they have a tremendous impact on our universe, with dark matter exerting a gravitational pull and dark energy driving the universe’s accelerating expansion.

What scientists know about dark matter and dark energy comes from observing their effects on the visible universe. Astrophysicists from the University of Chicago have measured those effects on a new patch of sky to illuminate the invisible cosmos.

Lightning channels reveal hidden bursts: Lateral negative re-discharges observed for first time

A new study led by researchers from the Institute of Atmospheric Physics of the Chinese Academy of Sciences (CAS) has uncovered the first observational evidence of lateral negative re-discharges occurring on negative leader channels. Published recently in Geophysical Research Letters, the findings offer new insights into how lightning channels remain electrically active and how their structures evolve before and after a return stroke.

Prior to this research, negative-polarity lateral breakdowns had only been observed near the tips of positive leaders—never documented along negative leader channels.

Scientists develop a glasses-free 3D system with a little help from AI

Watching 3D movies and TV shows is a fun and exciting experience, where images leap out of the screen. To get this effect, you usually have to wear a special pair of glasses. But that could soon be a thing of the past as scientists have developed a new display system that delivers a realistic 3D experience without the need for any eyewear.

The main reason why we’ve waited so long for a screen like this is a tough physics rule called the Space-Bandwidth Product (SBP). To get a perfect 3D image, you need a big screen (the “space”) and a wide viewing area (the “bandwidth”) so the picture looks good even when you turn your head. Unfortunately, according to the rule, you can’t have both at the same time. If you make the screen big, the viewing angle shrinks. If you increase the viewing area, the TV must get smaller. All previous attempts to break this trade-off have failed. But not this time.

Frequent flares from TRAPPIST-1 could impact habitability of nearby planets

Like a toddler right before naptime, TRAPPIST-1 is a small yet moody star. This little star, which sits in the constellation Aquarius about 40 light-years from Earth, spits out bursts of energy known as “flares” about six times a day.

New research led by the University of Colorado Boulder takes the deepest look yet at the physics behind TRAPPIST-1’s celestial temper tantrums. The team’s findings could help scientists search for habitable planets beyond Earth’s solar system.

The researchers used observations from NASA’s James Webb Space Telescope and computer simulations (models) to understand how TRAPPIST-1 produces its flares—first building up magnetic energy, then releasing it to kick off a chain of events that launches radiation deep into space. The results could help scientists unravel how the star has shaped its nearby planets, potentially in drastic ways.

High-energy-density barocaloric material could enable smaller, lighter solid-state cooling devices

A collaborative research team from the Institute of Solid State Physics, the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, has discovered a high-energy-density barocaloric effect in the plastic superionic conductor Ag₂Te₁₋ₓSₓ

“This material shows a volumetric barocaloric performance far beyond that of most known inorganic materials,” said Prof. Tong Peng, who led the team, “Its high energy density makes it well-suited for smaller and lighter cooling devices.”

The findings were published online in Advanced Functional Materials.

A direct leap into terahertz: Dirac materials enable efficient signal conversion at room temperature

Highspeed Internet, autonomous driving, the Internet of Things: data streams are proliferating at enormous speed. But classic radio technology is reaching its limits: the higher the data rate, the faster the signals need to be transmitted.

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have now demonstrated that weak radio signals can be efficiently converted into significantly higher frequencies using this material that is just several tens of nanometers thick. And at room temperature, at that. The results open up prospects for future generations of mobile communications and high-resolution sensor technology. The paper is published in the journal Communications Physics.

The more data to be transmitted simultaneously, the higher the carrier frequency must be. As a result, research is now delving into the terahertz range. This frequency spectrum lies outside the microwave range currently used and, so far, has been difficult to access technologically.

Long-standing puzzle in electron scattering deepens with new measurement

Why does lead behave so differently from every other atomic nucleus when struck by electrons? A team of physicists at Johannes Gutenberg University Mainz (JGU) has taken an important step toward answering this question, only to find that the mystery is even deeper than previously thought. The findings were published in the journal Physical Review Letters.

Electrons usually scatter from atomic nuclei in ways that can be predicted with remarkable accuracy. One well-tested feature is that flipping the spin of the incoming electrons should slightly change the scattering pattern, an effect driven by the exchange of two “virtual photons” between the electron and the nucleus.

For most nuclei, theory predicts exactly how large this tiny effect should be, and decades of experiments have confirmed those predictions. Lead, however, has always stood out. Earlier measurements performed at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility showed that, for lead, this spin-dependent effect seemed to vanish entirely, a result that no existing theory could explain.

I was asked to keep this confidential

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I want to read you an email that I was asked to keep confidential because I think it explains some of my worries about academia.

The Nature Physics comment is here: https://www.nature.com/articles/nphys4079

I knew that physicists would go on to argue I should have tried to solve the problem internally (within the community) before drawing public attention to it. The reason I published this comment was so that I could later demonstrate that I did this. This is why it’s a paywalled publication that you don’t find on the arxiv. But just by accident and totally unrelated here is another link:

https://www.dropbox.com/scl/fi/5o31k2jovu4nmyy219tzh/nphys40…22uph&dl=0

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Continue reading “I was asked to keep this confidential” | >

How Ramanujan’s formulae for pi connect to modern high energy physics

Most of us first hear about the irrational number π (pi)—rounded off as 3.14, with an infinite number of decimal digits—in school, where we learn about its use in the context of a circle. More recently, scientists have developed supercomputers that can estimate up to trillions of its digits.

Now, physicists at the Center for High Energy Physics (CHEP), Indian Institute of Science (IISc) have found that pure mathematical formulas used to calculate the value of pi 100 years ago has connections to fundamental physics of today—showing up in theoretical models of percolation, turbulence, and certain aspects of black holes.

The research is published in the journal Physical Review Letters.

Seeing physics as a mountain landscape for classification of nonlinear systems

Imagine standing on top of a mountain. From this vantage point, we can see picturesque valleys and majestic ridges below, and streams wind their way downhill. If a drop of rain falls somewhere on this terrain, gravity guides it along a path until it settles in one of the valleys. The trajectory traced by this droplet is known as a flow line, a path that indicates the direction of movement determined by the landscape’s gradient.

The complete network of valleys, ridges, and flow lines forms a topographic (or cartographic) map that captures the organization of the landscape. This organization, which remains stable as long as the terrain does not change, corresponds to a kind of “topological invariant,” as physicists would call it: It characterizes the global structure of the flows without reference to local details.

Now imagine that a jolt goes through the landscape and it changes, with new valleys appearing, others merging and ridges shifting. The flow lines reorganize accordingly, forming a new pattern of connections. Comparing these patterns—like two maps placed next to each other—reveals how the system’s topology evolves when its underlying conditions change.

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