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Piezoelectric materials enable a new approach to searching for axions

Dark matter, a type of matter that does not emit, reflect or absorb light, is predicted to account for most of the matter in the universe. As it eludes common experimental techniques for studying ordinary matter, understanding the nature and composition of dark matter has so far proved very challenging. One hypothesis is that it is made up of hypothetical particles known as quantum chromodynamics (QCD) axions. These are theoretical elementary particles that would interact very weakly with ordinary matter and are predicted to be extremely light, highly stable and electrically neutral.

While several large-scale studies have searched for small signals or effects that would indicate the presence of these particles or their interaction with ordinary matter, their existence has not yet been confirmed experimentally. In a paper recently published in Physical Review Letters, researchers at Perimeter Institute, University of North Carolina, Kavli Institute and New York University have introduced a new approach to search for QCD axions using a class of materials that generate electric fields when deformed, called piezoelectric materials.

“The axion was proposed in the late 1970s by Weinberg and Wilczek, as a solution to the strong CP (Charge-Parity) problem, a long-standing puzzle in the theory of the strong nuclear force,” Amalia Madden, co-senior author of the paper, told Phys.org.

Black Holes May Not Be What We Thought

Brian Greene and physicist Samir Mathur explore one of the deepest puzzles in modern physics, the true nature of black holes and the fate of information in the universe.

Their conversation centers on the black hole information paradox, a problem that has challenged physicists for decades. If quantum mechanics says information can never be destroyed, how can black holes once thought to erase everything that falls into them be reconciled with that principle? Mathur introduces the fuzzball theory, a proposal from string theory suggesting that black holes are not empty regions but complex structures that preserve information.

Greene and Mathur also revisit key developments in black hole physics, from entropy and Hawking radiation to modern ideas like firewalls and wormholes. They reflect on why certain approaches may fall short and whether recent theoretical insights are bringing the paradox closer to resolution. This conversation offers an engaging look at how physicists are rethinking black holes, quantum gravity, and the fundamental structure of reality.

This program is part of the Rethinking Reality series, supported by the John Templeton Foundation.

Participant: Samir Mathur.
Moderator: Brian Greene.

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How a One-in-a-Billion Mistake Made the Universe Possible

Huge thanks to KiwiCo for sponsoring today’s video! Go to https://www.kiwico.com/spacetime and use code SPACETIME for 50% off your first monthly crate.

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• Why Norway’s Osmosis Power Plant Failed.

At one-one-thousandth of a second after the Big Bang, the great annihilation event should have wiped out all matter, leaving a universe of only radiation. Why still don’t know why any matter survived. Well, a new finding from the LHC brings us one step closer to understanding why there’s something rather than nothing.

Dr. Caplan Paper for Review:
https://arxiv.org/abs/2312.

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Unusual signal may prove existence of primordial black holes

It may well take years to prove, but a pair of University of Miami astrophysicists could be on the verge of a cosmic breakthrough that will confirm the existence of primordial black holes and the role they play in one of cosmology’s greatest mysteries.

Believed to have formed within the first fraction of a second after the Big Bang, primordial black holes are purely theoretical. But if confirmed, these hypothetical cosmic phenomena, which could range from asteroid-sized to massive, could explain a lot, including the nature of dark matter—the invisible substance that constitutes about 85% of all matter in the universe, acting as “gravitational glue” that holds galaxies together.

“We believe our study will aid in confirming that they actually do exist,” Nico Cappelluti, an associate professor in the College of Arts and Sciences’ Department of Physics, said of the research he and Ph.D. student Alberto Magaraggia have conducted.

XRISM clocks hot wind of galaxy M82 at 2 million mph

For the first time, astronomers have directly measured the speed of superheated gas billowing from a cauldron of stellar activity at the heart of M82, a nearby galaxy undergoing an extraordinary burst of star formation. The material is moving more than 2 million miles (over 3 million kilometers) per hour and appears to be the primary force driving a cooler, well-studied, galaxy-scale wind.

Researchers made the calculations using data from the Resolve instrument aboard the XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft.

“The classic model of starburst galaxies like M82 suggests that shock waves from star formation and supernovae near the center heat gas, kick-starting a powerful wind,” said Erin Boettcher, an astrophysicist at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Astronomers Detect Strange “Chirp” From a Supernova, Revealing Hidden Physics

Astronomers studying a distant superluminous supernova uncovered a strange pattern hidden in its light: a rapidly accelerating “chirp.” For decades, astronomers have used distant supernova explosions as cosmic beacons to study fundamental physics and measure properties of the universe. While exam

New ultra-fast particle detector could help unmask dark matter

The CMS experiment at CERN is building a new detector that will unravel the chaotic particle collisions at the Large Hadron Collider, helping scientists identify particles based on their speeds.

What if Olympic officials could record sprinters’ times only to the nearest minute? “We would know who started the race, and who finished the race, but that’s it,” said Bryan Cardwell, a postdoctoral researcher at the University of Virginia. “There’s no way to know who arrived first and who arrived last.”

Cardwell and his colleagues on the CMS experiment are currently tackling a similar problem. The CMS experiment records the tracks and properties of subatomic particles created by the Large Hadron Collider, the world’s most powerful particle accelerator. As it stands, physicists get a picture of all the particles produced in a collision, but they have insufficiently detailed information about when the particles were produced or how fast they were traveling, making it difficult to tell them apart.

Distant galaxy fades 20-fold in just two decades, challenging how supermassive black holes evolve

An international team led by a researcher at the Chiba Institute of Technology has discovered an extremely rare phenomenon: a galaxy about 10 billion light-years away whose brightness dropped to one-twentieth of its original level in just 20 years. By combining multiwavelength observations with archival data spanning several decades, the researchers concluded that the fading was caused by a rapid decrease in the gas flowing into the supermassive black hole at the galaxy’s center. The discovery shows that the activity of supermassive black holes can change dramatically on timescales short enough to be observed within a human lifetime.

Most galaxies host at their centers a supermassive black hole, with a mass hundreds of millions of times that of the sun. In some cases, surrounding gas is pulled inward by the black hole’s strong gravity. As the gas spirals toward the black hole, it forms a structure known as an accretion disk. Friction in the disk heats the gas to extremely high temperatures, producing enormous amounts of energy. As a result, the center of the galaxy shines very brightly (see left image below). Such luminous regions are known as active galactic nuclei (AGN).

However, if the flow of gas into the accretion disk weakens for some reason, the emitted radiation decreases and the galactic center becomes dimmer (see right image below). The new observations suggest that this galaxy has entered exactly such a phase—one in which the activity of its central black hole has rapidly declined.

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