Archive for the ‘cosmology’ category: Page 169

Jun 12, 2022

Imaging Milky Way’s black hole: The exciting story began 100 years ago!

Posted by in category: cosmology

Jun 12, 2022

A collision that shook the universe! The first detection of a black hole gulping a neutron star

Posted by in category: cosmology

Jun 11, 2022

Contrasting the fuzzball and wormhole paradigms for black holes

Posted by in categories: cosmology, evolution, quantum physics

Circa 2021 Evidence of string theory by black holes as fuzzballs.

Abstract: We examine an interesting set of recent proposals describing a ‘wormhole paradigm’ for black holes. These proposals require that in some effective variables, semiclassical low-energy dynamics emerges at the horizon. We prove the ‘effective small corrections theorem’ to show that such an effective horizon behavior is not compatible with the requirement that the black hole radiate like a piece of coal as seen from outside. This theorem thus concretizes the fact that the proposals within the wormhole paradigm require some nonlocality linking the hole and its distant radiation. We try to illustrate various proposals for nonlocality by making simple bit models to encode the nonlocal effects. In each case, we find either nonunitarity of evolution in the black hole interior or a nonlocal Hamiltonian interaction between the hole and infinity; such an interaction is not present for burning coal. We examine recent arguments about the Page curve and observe that the quantity that is argued to follow the Page curve of a normal body is not the entanglement entropy but a different quantity. It has been suggested that this replacement of the quantity to be computed arises from the possibility of topology change in gravity which can generate replica wormholes. We examine the role of topology change in quantum gravity but do not find any source of connections between different replica copies in the path integral for the Rényi entropy. We also contrast the wormhole paradigm with the fuzzball paradigm, where the fuzzball does radiate like a piece of coal. Just as in the case of a piece of coal, the fuzzball does not have low-energy semiclassical dynamics at its surface at energies $E\sim T$ (effective dynamics at energies $E\gg T$ is possible under the conjecture of fuzzball complementarity, but these $E\gg T$ modes have no relevance to the Page curve or the information paradox).

From: Marcel Hughes [view email]

Jun 11, 2022

A ‘ghost’ black hole is moving around relatively nearby, scientists say

Posted by in category: cosmology

Scientists may have found the first “free-floating” black hole, as it moves around our Milky Way galaxy.

When large stars collapse, they are thought to leave behind black holes. If that is the case, there should be hundreds of millions scattered throughout the Milky Way, left behind after the death of those stars.

But scientists have struggled to find them. Isolated black holes are invisible.

Jun 10, 2022

Synapse Study Explores the “Dark Matter of the Brain”

Posted by in categories: biological, chemistry, cosmology, neuroscience

They are part of the brain of almost every animal species, yet they remain usually invisible even under the electron microscope. “Electrical synapses are like the dark matter of the brain,” says Alexander Borst, director at the MPI for Biological Intelligence, in foundation (i.f). Now a team from his department has taken a closer look at this rarely explored brain component: In the brain of the fruit fly Drosophila, they were able to show that electrical synapses occur in almost all brain areas and can influence the function and stability of individual nerve cells.

Neurons communicate via synapses, small contact points at which chemical messengers transmit a stimulus from one cell to the next. We may remember this from biology class. However, that is not the whole story. In addition to the commonly known chemical synapses, there is a second, little-known type of synapse: the electrical synapse. “Electrical synapses are much rarer and are hard to detect with current methods. That’s why they have hardly been researched so far,” explains Georg Ammer, who has long been fascinated by these hidden cell connections. “In most animal brains, we therefore don’t know even basic things, such as where exactly electrical synapses occur or how they influence brain activity.”

An electrical synapse connects two neurons directly, allowing the electrical current that neurons use to communicate, to flow from one cell to the next without a detour. Except in echinoderms, this particular type of synapse occurs in the brain of every animal species studied so far. “Electrical synapses must therefore have important functions: we just do not know which ones!” says Georg Ammer.

Jun 10, 2022

Scientists discovered a never-before-seen particle and it could be dark matter

Posted by in categories: cosmology, particle physics

Extremely interested to hear some of your opinions on this. Published in the journal Nature.

Scientists have discovered a new, mysterious particle. Of course, making new discoveries is exciting. But, perhaps the most exciting thing about this particle is that it could be a candidate for dark matter.

Incredibly, the never-before-seen particle was discovered using an experiment small enough to fit on a kitchen counter.

Continue reading “Scientists discovered a never-before-seen particle and it could be dark matter” »

Jun 8, 2022

Weather satellite sheds light on ‘Great Dimming’ of Betelgeuse star

Posted by in category: cosmology

Chance observations corroborate hybrid explanation for drop in brightness.

A weather satellite has helped explain why the red supergiant star Betelgeuse experienced an unprecedented dimming in 2019–20.

Its findings corroborate earlier studies that concluded the dimming was the consequence of a lower-temperature spot on the star, which reduced the heat going to a nearby gas cloud. This, astronomers believe, allowed the cloud to cool and condense into dust that blocked some of Betelgeuse’s light.

Continue reading “Weather satellite sheds light on ‘Great Dimming’ of Betelgeuse star” »

Jun 8, 2022

Elusive particle discovered in a material through tabletop experiment

Posted by in categories: cosmology, particle physics, quantum physics

An interdisciplinary team led by Boston College physicists has discovered a new particle—or previously undetectable quantum excitation—known as the axial Higgs mode, a magnetic relative of the mass-defining Higgs Boson particle, the team reports in the online edition of the journal Nature.

The detection a decade ago of the long-sought Higgs Boson became central to the understanding of mass. Unlike its parent, axial Higgs mode has a , and that requires a more complex form of the theory to explain its properties, said Boston College Professor of Physics Kenneth Burch, a lead co-author of the report “Axial Higgs Mode Detected by Quantum Pathway Interference in RTe3.”

Theories that predicted the existence of such a mode have been invoked to explain “,” the nearly invisible material that makes up much of the universe, but only reveals itself via gravity, Burch said.

Jun 7, 2022

Scientists found a new way to show us how the early universe formed

Posted by in categories: cosmology, information science, robotics/AI

Understanding the early universe has been a goal for scientists for decades. And, now with NASA’s James Webb space telescope, and other technology, we’re finally making some decent strides. A new simulation on early galaxy formation could be another key stepping stone, too.

Researchers created the simulation using machine learning. It then completed over 100,000 hours of computations to create the one-of-a-kind simulation. The researchers named the algorithm responsible for the project Hydo-BAM. They published a paper with the simulation’s findings earlier this year.

Creating a simulation of early galaxy formation has allowed researchers to chart the earliest moments of our universe. These important moments began just after the Big Bang set everything into motion. Understanding these key moments of the formation of the early universe could help us better understand how galaxies form in the universe today.

Jun 6, 2022

How the universe got its magnetic field?

Posted by in category: cosmology

All cosmic objects are embedded in magnetic fields. However, these fields are weak, but they are dynamically significant because they have profound effects on the dynamics of the universe.

The origin of these cosmic magnetic fields remains one of the most fundamental mysteries in cosmology, despite decades of intensive attention and inquiry.

By studying the dynamics of plasma turbulence, scientists from MIT are helping to solve one of the mysteries of the origins of cosmological magnetic fields.