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Periodic time for a generic soliton solution

  1. Jul 23, 2015 #1
    Hello everyone, I have a question regarding the possible periodicity of time in a generic metric.
    Suppose that for some reason I have a solution to Einstein's equations of the kind (in Euclidean time):


    Am I always allowed to assign some periodicity to the Eucledean time ##t_E## or is there any restriction?

    For example, I know that there is a particular solution called "thermal AdS" which is nothing but the usual AdS metric (i.e. not a black hole with an horizon) to which a periodic time has been assigned.

    When can I do that?

  2. jcsd
  3. Jul 23, 2015 #2


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    A periodic euclidean time is equivalent to gluing the two ends of the path integral that prepares your state. This is then equivalent to preparing a thermal state. So periodic Euclidean time is always going to prepare a thermal state via the path integral. Whether or not it is a black hole depends on the actual path integral.

    Note when I say path integral I mean that of the boundary CFT. So yes AdS and thermal AdS are the same as far as space-time geometry is concerned but in the latter the CFT is prepared in a thermal state. Black holes in the bulk are also dual to thermal CFTs (at least in most examples e.g. BTZ).

    EDIT: I forgot to mention that the path integrals for thermal AdS and BTZ are closely related. In the former the path integral is a torus with one circle parametrized by Euclidean time and the other by the angular coordinate; the latter can be obtained simply by switching the roles of these two coordinates on the torus.
    Last edited: Jul 23, 2015
  4. Jul 23, 2015 #3
    Thanks a lot for your reply! I guess my question was: since periodic Eucledean time always means thermal state for the boundary CFT, does this mean that if I have a generic soliton solution (no horizon) and I impose the time to be periodic this is going to be a thermal state? Do I have any constrain on the solution in order to be allowed to impose periodic time conditions?

    Thanks a gain!
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