Far out cosmology: string theory and inflation fight (Introduction)

by David Turell , Friday, March 27, 2020, 18:21 (1700 days ago) @ David Turell

Inflation won't fit into string theory:

https://www.scientificamerican.com/article/will-string-theory-finally-be-put-to-the-exp...

"Theorists have had difficulty, though, showing how, or if, inflation works in string theory. The most promising road to doing so—the so-called KKLT construction—does not convince everyone. “It depends who you ask,” says Suddhasattwa Brahma, a cosmologist at McGill University. “It has been a lingering doubt in the back of the minds of many in string theory: Does it really work?”
In 2018 a group of string theorists took a series of suggestive results and argued that this difficulty reflected an impossibility—that perhaps inflation just cannot happen in the theory.

"This so-called de Sitter swampland conjecture claimed that any version of the concept that could describe de Sitter space—a term for the kind of universe in which we expect inflation to take place—would have some kind of technical flaw that put it in a “swampland” of rejected theories.

"No one has proved the swampland conjecture, and several string theorists still expect that the final form of the theory will have no problem with inflation. But many believe that although the conjecture might not hold up rigidly, something close to it will. Brahma hopes to refine the swampland conjecture to something that would not bar inflation entirely.

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"These kinds of questions led Vafa and his Harvard collaborator Alek Bedroya to seek out a physics-based reason that could justify the swampland conjecture. They found a candidate in a surprising place. It turns out that inflation already has an unsolved problem looking for a solution: theorists have not all agreed on what happens to the very tiniest quantum details when expansion occurs and magnifies the static of the vacuum.

"Physicists lack a working theory that describes the world below the level of the so-called Planck length, an extremely minute distance where they expect the quantum side of gravity to appear. Proponents of inflation have typically had to assume that they can one day work those “trans-Planckian” details into it and that they will not make a big difference to any predictions. But how that step will happen remains an open question.

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From Rob Sheldon at uncommon descent: "Our physics color commentator, Rob Sheldon, author of The Long Ascent I and The Long Ascent II, offers, “This article explains precisely why thousands of theoretical physicists have not made any progress in 40 years. One hopelessly ad hoc and unsupported theory (inflation) conflicts with another hopelessly unphysical theory (string theory) and then others purport to resolve the difficulty by resorting to highly questionable phenomena (gravity waves)."

https://uncommondescent.com/intelligent-design/has-a-way-been-found-to-test-string-theo...

Comment: Still fun and games in theoretical cosmology with no good theory in sight. God created and evolved the universe in His own hidden way.