Is there a way to take a string theory, and produce from it a string theory which does not contain gravity?
I.e., effectively remove the graviton and it's states from the theory.
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$\begingroup$ Maybe by not allowing closed strings? But that's damaging quite a bit of the theory... In effect, it's closed strings oscillations that are associated with a spin-2 massless particle, which in turn can be understood as a graviton (and hence lead to a string theory with gravity). But it doesn't come with a "label" saying "graviton" on it. $\endgroup$– DemostheneCommented Mar 16, 2015 at 9:57
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2$\begingroup$ See "little string theory". $\endgroup$– Mitchell PorterCommented Mar 16, 2015 at 10:29
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$\begingroup$ @Mitchell Porter, That really doesn't answer my question since little string theory ( AIUI ) is particular model, whereas my question is about string theories in general. $\endgroup$– Mouse.The.Lucky.DogCommented Mar 16, 2015 at 12:59
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1$\begingroup$ wouldn't removing gravity from string theory be a bit like charging an electric car with a gas-powered generator? It might still get the job done, but you've removed a large part of what makes it an attractive option in the first place $\endgroup$– JimCommented Mar 16, 2015 at 14:16
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$\begingroup$ The general string theory contains the generic possibility of gravitons. You will always either define a different theory or go to particular model when you want no gravitons. It's the same as demanding that a generic gauge theory have only vanishing field strength, or that a generic QFT be renormalizable - you are restricting to particular models. $\endgroup$– ACuriousMind ♦Commented Mar 16, 2015 at 14:44
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1 Answer
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To my knowledge you have always a graviton in the closed string string spectrum.
The remaining option is to do a theory of only open strings. The problem now is that every loop interactions involves closed strings, so an open string theory is not consistent at the quantum level. See for instance the nice picture of p. 54, in Superstring Theory (Green, Schwarz, Witten)
Or, are you thinking something like a generalized GSO projection?
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$\begingroup$ In fact, removing the graviton was a central area of research when String Theory was first put forward as a theory of strong interactions in the 60s. It is known since then that there is no consistent way of truncating the spectrum in a way that the graviton is not present. $\endgroup$ Commented Jul 19, 2015 at 11:10