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FQXI ARTICLE

February 7, 2023

The Black Hole Universe

Is our universe housed in a black hole? Or did it exist before the Big Bang? If so, we could solve the mystery of dark energy—surprisingly, it’s all down to the humble neutrino.

FQXi Awardees: Stephon Alexander

May 28, 2010

STEPHON ALEXANDER

Haverford College

Let’s start with a little bit more about your assumed identity as a neutrino. Your mother was a proton who met up with three other protons deep inside a star. There was some nuclear fusion, she transformed herself into a neutron, and you popped out. You didn’t stick around very long, though. You have no charge and almost no mass, so you barely interact with the other particles, zipping through space, stars, and planets almost as if they aren’t even there.

So far, that’s the standard life story of a neutrino. But Stephon Alexander, a physicist at Haverford College, Pennsylvania, is shaking up that formulaic plot. What if, he ponders, time and our universe existed before the Big Bang? What if this prior version of the cosmos contracted down to a finite size, bounced, and started to expand outwards again? In that case, neutrinos, usually dismissed as being a ghostly particles with little tangible influence, could have had an extremely profound effect on the cosmos.

Subatomic Sardines

Picture yourself as a neutrino in such a contracting universe, wedged against other neutrinos like so many subatomic sardines, one hundred of you crowding every cubic centimeter of space. Under such circumstances, you and your comrades could form a new state of matter called a

Two types of physics—

neutrinos and dark energy

—appear to be built

from the same bedrock.

neutrinos and dark energy

—appear to be built

from the same bedrock.

- Stephon Alexander

A bouncing universe is only one possibility for how a neutrino condensate might form. Another is based on the notion that a collapsing star could squeeze neutrinos into a condensate, on its way to becoming a black hole. In that case, our universe might actually have formed in the neutrino soup housed inside a black hole.

A universe in a black hole may seem like an outlandish idea, but if correct, we still live within a neutrino condensate, which could be causing the expansion of the universe to accelerate. Astronomers have observed such an acceleration, and usually attribute it to some mysterious “dark energy.”

A strange parallel between neutrinos and dark energy gives Alexander a hint that he’s on the right trail. Neutrinos come in three

NEUTRINOS—DARK ENERGY’S

SECRET INGREDIENT?

The Sudbury Neutrino Observatory

(pictured) found that neutrinos

oscillate between three flavors.

Credit: NASA

Philip Phillips at the University of Illinois at Urbana-Champaign, an expert on what happens when exotic materials are squeezed down into new states of matter, finds the idea "truly novel." "Alexander has combined ideas from my field of condensed matter and put them to use in his own," he says.

While condensed matter physicists have produced examples of superfluids and condensates of other types of exotic matter, Alexander’s neutrino condensate cannot be cooked up in the lab because neutrinos are too slippery to capture and bundle together. But Alexander hopes to make testable predictions based on his theory that link the characteristics of neutrinos to the observed properties of dark energy. "We can use the universe as a laboratory to test particle physics," he says.

Lee Smolin, a theoretical physicist at the Perimeter Institute in Ontario, is a fan of Alexander’s original thinking. "He has a very fertile creativity combined with an independence of mind," he says.

So will neutrino condensation turn out to be the right answer to these cosmic riddles? Perhaps. As Smolin puts it, "We don’t know if it is true, but it is something that, so far as we know, might be true."

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BILLIONSNBILLIONS wrote on October 8, 2017

A black hole, according to Juan Maldacena, can be described by the 2-D event horizon surrounding it, every bit of information, spin, charge, etc, is mapped onto the horizon with one bit corresponding to one planck area of the event horizon. What this means is as a black hole consumes matter or energy, that information is added to the area of the event horizon, and because the event horizon is 2-d, and because the interior of a black hole is volume, as the size of a black hole grows, the density...

A black hole, according to Juan Maldacena, can be described by the 2-D event horizon surrounding it, every bit of information, spin, charge, etc, is mapped onto the horizon with one bit corresponding to one planck area of the event horizon. What this means is as a black hole consumes matter or energy, that information is added to the area of the event horizon, and because the event horizon is 2-d, and because the interior of a black hole is volume, as the size of a black hole grows, the density...

DURGADAS DATTA. wrote on June 27, 2016

The balloon inside balloon theory of matter and antimatter universes on opposite entropy path published in year 2003 has actually predicted that the outer antimatter universe is turning into a black hole gradually due to opposite entropy path. As such our universe is inside a black hole which is turning into a black hole. See the attached paper.

The balloon inside balloon theory of matter and antimatter universes on opposite entropy path published in year 2003 has actually predicted that the outer antimatter universe is turning into a black hole gradually due to opposite entropy path. As such our universe is inside a black hole which is turning into a black hole. See the attached paper.

BASIL ALTAIE wrote on April 21, 2011

As for the Black Hole Universe it might be useful to see the following article

[record/827653]

As for the Black Hole Universe it might be useful to see the following article

[record/827653]

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