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

Non-perturbative theory and perturbative theory

  1. Aug 18, 2010 #1
    Why is the string theory said to be a perturbative theory, while the LQG is a non-perturbative theory?
  2. jcsd
  3. Aug 18, 2010 #2
  4. Aug 18, 2010 #3
    I do not think string theory is perturbative. Many crucial phenomena in string theory like the existence of D-branes, S-duality, AdS/CFT and so on are non-perturbative.
  5. Aug 18, 2010 #4
    String theory is perturbative, S-Duality, D-branes and AdS/CFT Correspondence stem from Superstring Theory - a Perturbation Theory
  6. Aug 18, 2010 #5
    Look at this review,

    "An Introduction to Non-perturbative String Theory", Ashoke Sen


    It reviewed the non-perturbative part of string theory which was new at that time and now becomes the familiar parts of textbooks.
  7. Aug 18, 2010 #6
    For example, by using perturbative series, you will never get S-duality because one side has coupling g and the other side has coupling 1/g, so perturbative series can at most work on one side and cannot see the equivalence.

  8. Aug 18, 2010 #7
  9. Aug 18, 2010 #8
    My viewpoint is that now things change. 20 years ago, we only knew that string theory was describing the perturbation around a fixed background and it is true that before 1995, majority of string theory formulation was perturbative. But now with the dramatic developments, especially AdS/CFT, we see that string theory describes both the perturbative region and the non-perturbative region. The string perturbative series loses its importance in string theory.
  10. Aug 18, 2010 #9
    Yes, I absolutely agree that Superstring Theory is becoming more non-perturbative with the development of M-Theory, Gauge-Gravity Dualities (AdS/CFT, dS/CFT, Kerr/CFT...), Symmetries in nature/mathematics as well as various String Dualities. What I'm trying to say is that the core of Superstring theory, pre-1995/1997, was mostly perturbative.
  11. Aug 18, 2010 #10
    stupid question: why a perturbative theory cannot be background independant? thx.
  12. Aug 18, 2010 #11
  13. Aug 18, 2010 #12
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook