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Is gravity deterministic or probabilistic in String Theory?

  1. May 7, 2015 #1
    Layman question here: When discussing the difficulties in merging GR and Quantum theory, it is often mentioned that a main issue is that GR is continuous while quantum theory is discrete. A less commented point is the fact that GR is a deterministic theory while quantum theory is probabilistic.
    Since the probabilistic nature of quantum mechanics seems indisputable and string theory claims to be able to merge both, I assume that string theory is a probabilistic theory too, right?. Does this mean that gravity becomes also probabilistic in nature in string theory?
  2. jcsd
  3. May 7, 2015 #2


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    Yes, gravity is probabilistic in string theory.
  4. May 7, 2015 #3


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    Even more generally, any theory of quantum gravity in which the gravitational force is mediated by one or more fundamental particles (called by convention, "gravitons") such as the spin-2 massless graviton of string theory, or the spin-2 massive graviton of massive graviton theories is probabilistic also known as "stochastic".

    The stochastic nature of gravity in quantum gravity theories, however, usually has much less phenomenological relevance in quantum gravity phenomenology than it does in other parts of quantum physics, because there are very few situations where gravitons are encountered in isolation or in small numbers, and quantum tunneling is far less often relevant in quantum gravity than in other areas of quantum physics.
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