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I Lorentz violation, multiple preferred frames, vacuum energy

  1. Jan 16, 2017 #1
    Hi all - hope I'm not beating a dead horse here, but I'm following up on at least two other threads (made sense to consolidate):

    There are theories of quantum gravity (or the Standard Model Extension) that allow for local Lorentz violation. So, my first question: is there any reason why there has to be one preferred frame (across the whole universe). Could there not be multiple preferred frames, if, e.g., the values of fundamental 'constants' changed in both space and time?

    My second question follows from another thread in which I asked whether, in a universe where Lorentz symmetry is broken, one would expect to see different vacuum energies when moving in different directions. The relevant thread is here:

    https://www.physicsforums.com/threads/lorentz-violation-and-the-physical-vacuum.900243/

    Now, if one did see different vacuum energies (non-zero vacuum expectation values), one would expect to see particles when moving in certain directions, while not in others, no? Haelfix kindly commented on this:

    I'm wondering if anyone has any input on this? Final question: given the constraints on Lorentz violation established so far, it must the be case that, were it true that differences in vacuum energy existed, these differences must be very small or they would have been detected in laboratory experiments (i.e., I should not expect that, by moving in a certain direction, I run into a bunch of electrons or protons, etc.).

    Thanks all - sorry for the lengthy post. It seems the more you dig, the more interesting things become.
     
    Last edited: Jan 16, 2017
  2. jcsd
  3. Jan 16, 2017 #2
    Or perhaps just the first question, if there's no clear answer to the second?
     
  4. Jan 16, 2017 #3

    PeterDonis

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    Can you give some specific references? The answer to your question will depend on which specific theory you want to ask about.

    If they do, they can give it in the other thread.

    Yes, this is correct.
     
  5. Jan 16, 2017 #4
    Thanks PeterDonis - let me find a couple of candidate theories to ask about.

    Regarding the last response - from current constraints on Lorentz possible violation, if vacuum energy did have a directional component, would it be possible to place a bound on the magnitude of that component? In turn, based on the (directional) vacuum expectation value, could one then estimate the expected number of low energy photons, electrons, etc. encountered when moving in that direction (per unit time)? (which might inform how long a laboratory experiment would have to make observations in order to identify the directional component)
     
  6. Jan 16, 2017 #5

    PeterDonis

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    I'm not sure how one would do this; I haven't seen this question treated in any discussion of Lorentz violations.
     
  7. Jan 17, 2017 #6
    I wonder if Prof. Neumaier might have any thoughts? It seems like this would be one question to ask, so given that PeterDonis hasn't seen this in any discussion of Lorentz violation, perhaps there's a reason why the vacuum energy must be the same in all directions.
     
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