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Category: cosmology – Page 109

Beyond Gravity: UC Berkeley’s Quantum Leap in Dark Energy Research

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Researchers at UC Berkeley have enhanced the precision of gravity experiments using an atom interferometer combined with an optical lattice, significantly extending the time atoms can be held in free fall. Despite not yet finding deviations from Newton’s gravity, these advancements could potentially reveal new quantum aspects of gravity and test theories about exotic particles like chameleons or symmetrons.

Twenty-six years ago physicists discovered dark energy — a mysterious force pushing the universe apart at an ever-increasing rate. Ever since, scientists have been searching for a new and exotic particle causing the expansion.

Pushing the boundaries of this search, University of California, Berkeley physicists have now built the most precise experiment yet to look for minor deviations from the accepted theory of gravity that could be evidence for such a particle, which theorists have dubbed a chameleon or symmetron.

Brian Greene: The Most Important Question in Science

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What would Brian Greene do if he could travel through time, and which future technology is he most excited about?

After our full interview, I had the privilege to sit down with Brian and ask him a few more questions. Enjoy this exclusive Q\&A with one of the most renowned physicists of our time!

And if you haven’t already, check out our full interview: • Brian Greene: The Truth About String…

Brian Greene is an American theoretical physicist and mathematician. He’s a professor at Columbia University and the director of Columbia’s Center for Theoretical Physics. He has gained a lot of popularity through his books that bring complex physical issues closer to general audiences: The Elegant Universe (1999), Icarus at the Edge of Time (2008), The Fabric of the Cosmos (2004), and The Hidden Reality (2011), a book he promoted in the TV show The Big Bang Theory!

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Epic Expansion: The Case for Inflationary Cosmology

For decades, inflation has been the dominant cosmological scenario, but recently the theory has been subject to competition and critique. Two renowned pioneers of inflation — Alan Guth and Andrei Linde — join Brian Greene to make their strongest case for the inflationary theory.

This program is part of the Big Ideas series, supported by the John Templeton Foundation.

Participants:
Alan Guth.
Andrei Linde.

Moderator:
Brian Greene.

00:00 — Introduction.
05:58 — Participant introductions.
08:23 — Problems with the Big Bang.
28:07 — Realizing the Inflationary Paradigm.
42:13 — Observational Support for the Inflationary Theory.
56:37 — Eternal Inflation and the Measure Problem.
01:17:09-The Future of Cosmology.

Quantum effects forbid the formation of black holes from high concentrations of intense light, say physicists

For the last seven decades, astrophysicists have theorized the existence of “kugelblitze,” black holes caused by extremely high concentrations of light.

These special black holes, they speculated, might be linked to astronomical phenomena such as , and have even been suggested as the power source of hypothetical spaceship engines in the far future.

However, new research by a team of researchers at the University of Waterloo and Universidad Complutense de Madrid demonstrates that kugelblitze are impossible in our current universe. Their research, titled “No black holes from ,” is published on the arXiv preprint server and is forthcoming in Physical Review Letters.

Scientists are getting closer to proving the multiverse exists

The universe is a massive place, with galaxies well beyond our own. However, some also hypothesize that there may be more than one universe. The multiverse theory essentially suggests that our universe is just one of many branching and infinite universes. These universes are believed to have appeared just after the Big Bang, and now, scientists may be closer than ever to proving this theory is correct.

The idea of a multiverse existing has gained a lot of following over the past several years—not only in entertainment avenues like the Marvel Cinematic Universe but also in the scientific community, especially since the 1980s when inflation—a period when the universe suddenly expanded—was invented. Inflation is the main explanation for why the universe is so smooth and flat. It also predicts the existence of several independent universes beyond our own.

But inflation isn’t the only route that scientists have looked at to prove the multiverse theory. Others have looked at alternatives called cyclic universes, which basically say the universe is on an unending cycle of ballooning and then compressing. It still focuses on that multiple universe prospect—though it focuses on them appearing at different times.

Black Holes and Dark Revelations: Gravitational Waves Provide New Clues to the Composition of Dark Matter

Note that this does not involve Planck mass fermionic black holes!

A population of massive black holes whose origin is one of the biggest mysteries in modern astronomy has been detected by the LIGO and Virgo gravitational wave detectors.

According to one hypothesis, these objects may have formed in the very early Universe and may compose dark matter, a mysterious substance filling the Universe. A team of scientists has announced the results of nearly 20-year-long observations indicating that such massive black holes may comprise at most a few percent of dark matter. Therefore, another explanation is needed for gravitational wave sources.

The results of the study were published in two articles, in Nature and the Astrophysical Journal Supplement Series. The research was conducted by scientists from the OGLE (Optical Gravitational Lensing Experiment) survey from the Astronomical Observatory of the University of Warsaw.

Various astronomical observations indicate that ordinary matter, which we can see or touch, comprises only 5% of the total mass and energy budget of the Universe. In the Milky Way, for every pound of ordinary matter in stars, there are 15 pounds of “dark matter,” which does not emit any light and interacts only through its gravitational pull.

The surprising behavior of black holes in an expanding universe

A physicist investigating black holes has found that, in an expanding universe, Einstein’s equations require that the rate of the universe’s expansion at the event horizon of every black hole must be a constant, the same for all black holes. In turn this means that the only energy at the event horizon is dark energy, the so-called cosmological constant. The study is published on the arXiv preprint server.

“Otherwise,” said Nikodem Popławski, a Distinguished Lecturer at the University of New Haven, “the pressure of matter and curvature of spacetime would have to be infinite at a horizon, but that is unphysical.”

Black holes are a fascinating topic because they are about the simplest things in the universe: their only properties are mass, electric charge and angular momentum (spin). Yet their simplicity gives rise to a fantastical property—they have an event horizon at a critical distance from the black hole, a nonphysical surface around it, spherical in the simplest cases. Anything closer to the black hole, that is, inside the event horizon, can never escape the black hole.

Experiment captures atoms in free fall to look for gravitational anomalies caused by dark energy

Dark energy—a mysterious force pushing the universe apart at an ever-increasing rate—was discovered 26 years ago, and ever since, scientists have been searching for a new and exotic particle causing the expansion.

Pushing the boundaries of this search, University of California, Berkeley physicists have now built the most precise experiment yet to look for minor deviations from the accepted theory of that could be evidence for such a particle, which theorists have dubbed a chameleon or symmetron. The results are published in the June 11, 2024, issue of Nature Physics.

The experiment, which combines an for precise gravity measurements with an to hold the atoms in place, allowed the researchers to immobilize free-falling atoms for seconds instead of milliseconds to look for gravitational effects, besting the current most precise measurement by a factor of five.

From the Dawn of Time: Hunting for Primordial Black Holes With NASA’s Roman Space Telescope

New studies suggest the Nancy Grace Roman Space Telescope could detect primordial black holes from the early universe, potentially confirming their role in cosmic inflation and as components of dark matter.

When astrophysicists observe the cosmos, they see different types of black holes. They range from gargantuan supermassive black holes with billions of solar masses to difficult-to-find intermediate-mass black holes (IMBHs) all the way down to smaller stellar-mass black holes.

But there may be another class of these objects: primordial black holes (PBHs) that formed in the very early Universe. If they exist, the Nancy Grace Roman Space Telescope should be able to spot them.

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