A change of vacuum in string theory?

[bcrowell]

As I understand it, string theory only has one coupling constant, but there is a whole discrete landscape of false vacua, each of which gives different values to the quantities, such as coupling constants, that are taken to be fixed inputs to the standard model. Since the false vacua are metastable, presumably the theory allows transitions from one false vacuum to another, but the half-life is extremely long -- what fixes this time-scale? If such a transition occurred, would we get a bubble of spacetime with different properties that would spread outward from some point at c? Would the new vacuum's properties differ dramatically from the old one's, or would you be more likely to get a relatively small change?

The motivation for this question is that if you believe (which I don't) Webb et al.'s claim that the fine structure constant varies over spacetime, then it would be interesting to understand whether string theory could accommodate such a change.

Is the choice of a false vacuum in string theory essentially synonymous with the choice of a background?

 

[atyy]

http://arxiv.org/abs/hep-th/0505232
Observational Consequences of a Landscape
Ben Freivogel, Matthew Kleban, Maria Rodriguez Martinez, Leonard Susskind

http://arxiv.org/abs/hep-th/0612083
Transitions Between de Sitter Minima
Puneet Batra, Matthew Kleban

http://arxiv.org/abs/0807.1104
Evidence for a bound on the lifetime of de Sitter space
Ben Freivogel, Matthew Lippert

http://arxiv.org/abs/0805.3705
Field dynamics and tunneling in a flux landscape
Matthew C Johnson, Magdalena Larfors

 

[bcrowell]

Thanks, atyy -- much appreciated!

My (probably totally inaccurate) characterization of the Freivogel paper is that absolutely nothing is known about the lifetime of false vacua in string theory. Is this totally inaccurate?

 

[Fra]

Since the false vacua are metastable, presumably the theory allows transitions from one false vacuum to another, but the half-life is extremely long -- what fixes this time-scale? If such a transition occurred, would we get a bubble of spacetime with different properties that would spread outward from some point at c? Would the new vacuum's properties differ dramatically from the old one's, or would you be more likely to get a relatively small change?

As far as I know these are key problems of ST, that are still formally unsolved. The vacuum selection principle is missing. Ie. the mechanism for somehow unambigously incorporating excitations around a background, into the background, is as far as I know still not known in ST.

IMHO, there are at least two different generals ways to interpret such a situation where the laws of nature changes. Different "universes" is only one of them. A more radical(more radical than smolins CNS) form of evolving law (within one universe) is the other.

This tangents to the discussion in the other thread.

/Fredrik