Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is spacetime needed in QG ?

  1. Jun 5, 2012 #1
    Hello forum!

    I would like to begin by stating that I am no expert in general relativity, nor in physics or mathematics, although I have some basic understanding of calculus and linear algebra. So if you can keep the math simple, I would appreciate. Also, please correct me if I'm wrong.

    As I understand so far, tensors are used to describe the curvature of spacetime due to the presence of mass. But this would imply that quantum effects are taking place on a manifold.
    My question is the following : Could tensors be used to describe the direction of quantum interactions on a macroscopic scale without the need of a spacetime with it's own geometry in the background?

    Thank you for your time.

    P.S : If this is in the wrong sub-forum and should be in ''Quantum Physics'', I apologize.
  2. jcsd
  3. Jun 5, 2012 #2


    User Avatar
    Science Advisor
    Gold Member

    Tensors exist on a manifold. The manifold in GR is spacetime. If you still want to use tensors, then you have to have a manifold. You could replace the spacetime manifold with something else if you want, but as long as you want tensors around, you need to have a manifold.

    If you want to try to formulate a quantum gravity without a manifold, then you will be without tensors. Nobody says that this is impossible. Nobody has found a consistent and compelling theory of quantum gravity yet, so I don't think we can rule things out at this point.
  4. Jun 6, 2012 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

  5. Jun 6, 2012 #4
    Thank you robphy! Very interesting indeed.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook