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New studies broaden understanding of black hole uniqueness

Physics that exist near the center of a black hole are being made to examine using the so-called "gravitational quantum loop" theory. The theory uses quantum mechanics to extend gravitational physics beyond Einstein's theory of general relativity.

It originated at Penn State and was adopted by scientists from around the world to explore new paradigms of modern physics. It is considered to be the best way to analyze extreme cosmological and astrophysical phenomena in parts of the universe, such as black holes.

New articles boost thinking

Two new documents do just that. Abhay Ashtekar and Penn Olmedo of Penn State and Parampreet Singh of Louisiana State University have published articles that span the work done that used quantum loop gravity to analyze the quantum nature of the Big Bang.

The new documents extend these results to the interiors of black holes. "The best theory of gravity we have today is general relativity, but it has limitations," said Ashtekar, Evan Pugh Professor of Physics, holder of the Eberly Family Chair in Physics, and director of the Penn State Institute of Gravitation and Cosmos.

"For example, general relativity predicts that there are places in the universe where gravity becomes infinite and space-time simply ends. We refer to these places as" singularities. "But even Einstein agreed that this limitation of general relativity results from fact of ignoring quantum mechanics ".

The theory of quantum gravitation in a loop extends the theory of relativity

Uniqueness can be understood as the result of space-time being so curved in the center of a black hole that, according to general relativity, space-time becomes curved and, ultimately, infinite.

This results in space-time with an irregular border, beyond that physical edge no longer exists and this is known as the singularity.

The Big Bang is another example of uniqueness. Under the picture of the general reality, it is impossible to ask what happened before the Big Bang because space-time ends, and there is not before.

Modifying Einstein's equations by means of loop quantum gravity allows researchers to push physics beyond the big bang to make new predictions.

Similar modifications that incorporated quantum mechanics through quantum loop gravity allowed the authors of the new articles to make new predictions for the black hole's singularity.

"The basis of looping quantum gravity is Einstein's discovery that space-time geometry is not only a stage in which cosmological events are staged but is itself a physical entity that can be folded" said Ashtekar.

"As a physical entity, space-time geometry is composed of some fundamental units, just as matter is composed of atoms. These geometry units – called "quantum excitations" – are orders of magnitude smaller than we can detect with today's technology, but we have precise quantum equations that predict their behavior, and one of the best places to look for its effects is in the center of a black hole.

The articles appear as "Editor's Tips" in the journals Physical Review Letters and Physical Review, December 10, 2018, and were also highlighted in a Viewpoint article in Physics magazine.

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