Mar 17, 2022 11:24 PM
(This post was last modified: Mar 18, 2022 07:08 PM by C C.)
Our universe may have a twin that runs backward in time
https://www.livescience.com/mirror-unive...ark-matter
EXCERPTS: A wild new theory suggests there may be another "anti-universe," running backward in time prior to the Big Bang. The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward.
If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe. And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang.
If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists.
Physicists have identified a set of fundamental symmetries in nature. [...] physicists have never observed a violation of a combination of all three symmetries at the same time. If you take every single interaction observed in nature and flip the charges, take the mirror image, and run it backward in time, those interactions behave exactly the same.
[...] In a new paper recently accepted for publication in the journal Annals of Physics, scientists propose extending this combined symmetry. Usually this symmetry only applies to interactions — the forces and fields that make up the physics of the cosmos. But perhaps, if this is such an incredibly important symmetry, it applies to the whole entire universe itself. In other words, this idea extends this symmetry from applying to just the "actors" of the universe (forces and fields) to the "stage" itself, the entire physical object of the universe.
[...] We would never have access to our twin, the CPT-mirror universe, because it exists "behind" our Big Bang, before the beginning of our cosmos. But that doesn't mean we can't test this idea. The researchers found a few observational consequences of this idea... (MORE - missing details)
‘Quantum hair’ could resolve Hawking’s black hole paradox, say scientists
https://www.theguardian.com/science/2022...scientists
EXCERPTS: Stephen Hawking’s black hole information paradox has bedevilled scientists for half a century and led some to question the fundamental laws of physics. Now scientists say they may have resolved the infamous problem by showing that black holes have a property known as “quantum hair”. If correct, this would mark a momentous advance in theoretical physics.
[...] the quantum hair theorem claims to resolve the paradox by bridging the gap between general relativity and quantum mechanics using a new mathematical formulation.
The name is a nod to the view, based on classical physics, that black holes can be viewed as surprisingly simple objects, defined only by their mass and speed of rotation. The prediction of bald, featureless black holes has been nicknamed the “no-hair theorem” since the 1970s.
Calmet and his collaborators think the black hole is more complex – or hairy. As matter collapses into a black hole, they suggest, it leaves a faint imprint in its gravitational field. This imprint is referred to as “quantum hair” and, the authors say, would provide the mechanism by which information is preserved during the collapse of a black hole. Under this theory, two black holes with identical masses and radii, but with different internal composition, would have very subtle differences in their gravitational fields.
“Our solution doesn’t require any speculative idea; instead our research demonstrates that the two theories can be used to make consistent calculations for black holes and explain how information is stored without the need for radical new physics,” said Calmet.
There is no obvious way to test the theory through astronomical observations – the gravitational fluctuations would be too tiny to be measurable. But the theory is likely to come under robust scrutiny from the theoretical community... (MORE - missing details)
https://www.livescience.com/mirror-unive...ark-matter
EXCERPTS: A wild new theory suggests there may be another "anti-universe," running backward in time prior to the Big Bang. The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward.
If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe. And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang.
If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists.
Physicists have identified a set of fundamental symmetries in nature. [...] physicists have never observed a violation of a combination of all three symmetries at the same time. If you take every single interaction observed in nature and flip the charges, take the mirror image, and run it backward in time, those interactions behave exactly the same.
[...] In a new paper recently accepted for publication in the journal Annals of Physics, scientists propose extending this combined symmetry. Usually this symmetry only applies to interactions — the forces and fields that make up the physics of the cosmos. But perhaps, if this is such an incredibly important symmetry, it applies to the whole entire universe itself. In other words, this idea extends this symmetry from applying to just the "actors" of the universe (forces and fields) to the "stage" itself, the entire physical object of the universe.
[...] We would never have access to our twin, the CPT-mirror universe, because it exists "behind" our Big Bang, before the beginning of our cosmos. But that doesn't mean we can't test this idea. The researchers found a few observational consequences of this idea... (MORE - missing details)
‘Quantum hair’ could resolve Hawking’s black hole paradox, say scientists
https://www.theguardian.com/science/2022...scientists
EXCERPTS: Stephen Hawking’s black hole information paradox has bedevilled scientists for half a century and led some to question the fundamental laws of physics. Now scientists say they may have resolved the infamous problem by showing that black holes have a property known as “quantum hair”. If correct, this would mark a momentous advance in theoretical physics.
[...] the quantum hair theorem claims to resolve the paradox by bridging the gap between general relativity and quantum mechanics using a new mathematical formulation.
The name is a nod to the view, based on classical physics, that black holes can be viewed as surprisingly simple objects, defined only by their mass and speed of rotation. The prediction of bald, featureless black holes has been nicknamed the “no-hair theorem” since the 1970s.
Calmet and his collaborators think the black hole is more complex – or hairy. As matter collapses into a black hole, they suggest, it leaves a faint imprint in its gravitational field. This imprint is referred to as “quantum hair” and, the authors say, would provide the mechanism by which information is preserved during the collapse of a black hole. Under this theory, two black holes with identical masses and radii, but with different internal composition, would have very subtle differences in their gravitational fields.
“Our solution doesn’t require any speculative idea; instead our research demonstrates that the two theories can be used to make consistent calculations for black holes and explain how information is stored without the need for radical new physics,” said Calmet.
There is no obvious way to test the theory through astronomical observations – the gravitational fluctuations would be too tiny to be measurable. But the theory is likely to come under robust scrutiny from the theoretical community... (MORE - missing details)
