Ohio State Department of Physics

HEP/Astro Seminar - Wednesday, 30 April 2003

Comments on Cosmological Singularities in String Theory

Dr. Govindan Rajesh (University of Chicago)


We compute string scattering amplitudes in an orbifold of Minkowski space by a boost, and show how certain divergences in the four point function are associated with graviton exchange near the singularity. These divergences reflect large tree-level backreaction of the gravitational field. Near the singularity, all excitations behave like massless fields on a 1+1 dimensional cylinder. For excitations that are chiral near the singularity, we show that divergences are avoided and that the backreaction is milder. We discuss the implications of this for some cosmological spacetimes. Finally, in order to gain some intuition about what happens when backreaction is taken into account, we study an open string rolling tachyon background as a toy model that shares some features with R1,1/Z.

15:30, Smith Lab 4079

Last updated 21 April 2003, Matthew Wingate

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