Apr 23, 2021 03:35 AM
(This post was last modified: Apr 23, 2021 05:09 PM by C C.)
How Maxwell’s demon continues to startle scientists
https://www.quantamagazine.org/how-maxwe...-20210422/
EXCERPT: . . . In 1982, the American physicist Charles Bennett put the pieces of the puzzle together. He realized that Maxwell’s demon was at core an information-processing machine: It needed to record and store information about individual particles in order to decide when to open and close the door. Periodically it would need to erase this information. According to Landauer’s erasure principle, the rise in entropy from the erasure would more than compensate for the decrease in entropy caused by the sorting of the particles. “You need to pay,” said Gonzalo Manzano, a physicist at the Institute for Quantum Optics and Quantum Information in Vienna. The demon’s need to make room for more information inexorably led to a net increase in disorder... (MORE - details)
'Exotic compact objects' could soon break physics, new study suggests
https://www.livescience.com/exotic-compa...ysics.html
EXCERPT: . . . The term "exotic compact object" encompasses a variety of different theoretical entities. Among the possibilities are gravastars, which would appear quite similar to an ordinary black hole but would be filled with dark energy, a mysterious substance causing the accelerated expansion of the universe. Another compact object that could lurk in the universe is a fuzzball, a black-hole-like knot of fundamental one-dimensional strings proposed in string theory, which attempts to unify and replace the current accepted theories in physics.
The thing that connects exotic compact objects is that, unlike a black hole, they should lack a region known as an event horizon, Longo said. According to Albert Einstein's theory of relativity, the event horizon is a sphere surrounding a black hole beyond which any trip becomes one-way. Objects can slip inside the event horizon but nothing can come out of it — not even light.
But scientists know that Einstein's theory of relativity will one day have to be replaced. Though the theory is extraordinarily successful at describing gravity and massive cosmic entities, it says nothing about the behavior of subatomic particles. For that, physicists turn to quantum mechanics.
The hope is to eventually have a theory of quantum gravity that supersedes both relativity and quantum mechanics. Exotic compact objects, which would be like a black hole but lack an event horizon, could help provide the necessary information to start constructing this future theory.
"They will break with general relativity because they won't give rise to one of its key predictions," Longo said, referring to the event horizon. "In this sense we would be testing Einstein's theory of gravitation."
As two black holes crash and merge, they spin around one another, warping space-time and sending out gravitational waves, which can ring LIGO's detectors on Earth. After they meet, the event horizon prevents additional waves from escaping outward, Longo said.
But because exotic compact objects would lack an event horizon, some gravitational waves could fall inward towards the object's center and then bounce back, creating gravitational echoes that leak outward, he added. These echoes are too faint for LIGO and Virgo to detect right now, but the facilities are currently being upgraded for increased sensitivity, and they’ve been joined by the Kamioka Gravitational Wave Detector (KAGRA) in Japan, which became operational last year.
Longo and his colleagues have calculated that during the gravitational wave detectors' next observation run, set to begin in the summer of 2022, LIGO and its counterparts could be sensitive enough to pick up the signal from one or two exotic compact objects, if they exist. Longo will present his team's findings at the American Physical Society's April meeting on April 19... (MORE - details)
https://www.quantamagazine.org/how-maxwe...-20210422/
EXCERPT: . . . In 1982, the American physicist Charles Bennett put the pieces of the puzzle together. He realized that Maxwell’s demon was at core an information-processing machine: It needed to record and store information about individual particles in order to decide when to open and close the door. Periodically it would need to erase this information. According to Landauer’s erasure principle, the rise in entropy from the erasure would more than compensate for the decrease in entropy caused by the sorting of the particles. “You need to pay,” said Gonzalo Manzano, a physicist at the Institute for Quantum Optics and Quantum Information in Vienna. The demon’s need to make room for more information inexorably led to a net increase in disorder... (MORE - details)
'Exotic compact objects' could soon break physics, new study suggests
https://www.livescience.com/exotic-compa...ysics.html
EXCERPT: . . . The term "exotic compact object" encompasses a variety of different theoretical entities. Among the possibilities are gravastars, which would appear quite similar to an ordinary black hole but would be filled with dark energy, a mysterious substance causing the accelerated expansion of the universe. Another compact object that could lurk in the universe is a fuzzball, a black-hole-like knot of fundamental one-dimensional strings proposed in string theory, which attempts to unify and replace the current accepted theories in physics.
The thing that connects exotic compact objects is that, unlike a black hole, they should lack a region known as an event horizon, Longo said. According to Albert Einstein's theory of relativity, the event horizon is a sphere surrounding a black hole beyond which any trip becomes one-way. Objects can slip inside the event horizon but nothing can come out of it — not even light.
But scientists know that Einstein's theory of relativity will one day have to be replaced. Though the theory is extraordinarily successful at describing gravity and massive cosmic entities, it says nothing about the behavior of subatomic particles. For that, physicists turn to quantum mechanics.
The hope is to eventually have a theory of quantum gravity that supersedes both relativity and quantum mechanics. Exotic compact objects, which would be like a black hole but lack an event horizon, could help provide the necessary information to start constructing this future theory.
"They will break with general relativity because they won't give rise to one of its key predictions," Longo said, referring to the event horizon. "In this sense we would be testing Einstein's theory of gravitation."
As two black holes crash and merge, they spin around one another, warping space-time and sending out gravitational waves, which can ring LIGO's detectors on Earth. After they meet, the event horizon prevents additional waves from escaping outward, Longo said.
But because exotic compact objects would lack an event horizon, some gravitational waves could fall inward towards the object's center and then bounce back, creating gravitational echoes that leak outward, he added. These echoes are too faint for LIGO and Virgo to detect right now, but the facilities are currently being upgraded for increased sensitivity, and they’ve been joined by the Kamioka Gravitational Wave Detector (KAGRA) in Japan, which became operational last year.
Longo and his colleagues have calculated that during the gravitational wave detectors' next observation run, set to begin in the summer of 2022, LIGO and its counterparts could be sensitive enough to pick up the signal from one or two exotic compact objects, if they exist. Longo will present his team's findings at the American Physical Society's April meeting on April 19... (MORE - details)