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Am I correct in understanding that in string theory before the birth of the universe, fundamental strings did not interact with each other, and when the strings began to interact, space-time appeared?

Qmechanic
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Arman Armenpress
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    Where did you read/hear/watch this? – G. Smith Oct 25 '20 at 19:31
  • In Brian Green's book – Arman Armenpress Oct 25 '20 at 19:39
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    Thanks. Can you provide the quote in addition to your paraphrase? – G. Smith Oct 25 '20 at 19:40
  • the quote is too long ((( It's in the chapter "What Are Space and Time, Really, and Can We Do without Them?" – Arman Armenpress Oct 25 '20 at 19:49
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    OK. We’ll have to make do with your paraphrase. I haven’t read the book so I don’t know whether you have understood Green correctly. But I am skeptical that this view is widely accepted. – G. Smith Oct 25 '20 at 19:51
  • graviton, the smallest bundle of gravitational force, is one particular pattern of string vibration. And just as an electromagnetic field such as visible light is composed of an enormous number of photons, a gravitational field is composed of an enormous number of gravitons—that is, an enormous number of strings executing the graviton vibrational pattern.Gravitational fields, in turn, are encoded in the warping of the spacetime fabric,and hence we are led to identify the fabric of spacetime itself with a colossal number of strings all undergoing the same, orderly,graviton pattern of vibration. – Arman Armenpress Oct 25 '20 at 19:55
  • In the language of the field, such an enormous, organized array of similarly vibrating strings is known as a coherent state of strings. It's a rather poetic image—the strings of string theory as the threads of the spacetime fabric—but we should note that its rigorous meaning has yet to be worked out completely. – Arman Armenpress Oct 25 '20 at 19:55
  • But in the raw state, before the strings that make up the cosmic fabric engage in the orderly, coherent vibrational dance we are discussing, there is no realization of space or time. Even our language is too coarse to handle these ideas, for, in fact, there is even no notion of before. In a sense, it's as if individual strings are "shards" of space and time, and only when they appropriately undergo sympathetic vibrations do the conventional notions of space and time emerge. – Arman Armenpress Oct 25 '20 at 19:57
  • But can quantum particles, including strings, absolutely not interact, and then suddenly begin to interact? – Arman Armenpress Oct 25 '20 at 20:32
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    Title: What Are Space and Time, Really, and Can We Do without Them? Page 171 – Arman Armenpress Oct 25 '20 at 20:44
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    But surely the strings are the universe? So if there are strings, then the universe is there already, by definition (in an early state). – Andrew Steane Oct 25 '20 at 20:51
  • Related: Do strings propagate through space time or do they make space time? – G. Smith Oct 25 '20 at 21:00
  • The quotes are from "The Elegant Universe" of Brian Geene, Chapter 15 "Prospects", subsection "What Are Space and Time, Really, and Can We Do without Them?" – Quillo Oct 25 '20 at 22:34

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Your question cannot be answered unless you specify exactly what concrete scenario you have in mind.

We haven't reached a complete understanding of how spacetime emerge in the context of string theory; because of that, all standard string inspired cosmologies assume preexisting backgrounds over which strings can propagate.

Some scenarios such as the string gas scenario take as work hypothesis a large system of weakly coupled strings, but others, such as brane inflation provide configurations where strings can interact at finite coupling.

Further references:

  1. R. H. Brandenberger, "String gas cosmology: progress and problems", Class. Quantum Grav. 28 204005 (2011), arXiv:1105.3247.
  2. Book "The Universe Before the Big Bang: Cosmology and String Theory" by Maurizio Gasperini, Springer (2008).
  3. L. McAllister and E. Silverstein, "String cosmology: a review", Gen. Rel. Grav. 40, 565-605 (2008), arXiv:0710.2951.
Urb
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Ramiro Hum-Sah
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  • What means strings can interact at finite coupling? – Arman Armenpress Oct 26 '20 at 06:32
  • It simply means that they are aoweed to interact. Brane models of inflation introduce scalars (inflatons) and build potentials for them from $D-$brane configurations. Generic $D$-brane configurations are described by interacting open strings attached to them. – Ramiro Hum-Sah Oct 26 '20 at 17:51