Magnetic backgrounds and tachyonic instabilities in closed superstring theory and M-theory

TL;DR

This paper explores magnetic flux backgrounds in superstring and M-theory, revealing how they interpolate between different string theories and addressing tachyonic instabilities through novel models and dualities.

Contribution

It introduces new magnetic flux backgrounds in string and M-theory, and provides a framework to understand tachyonic instabilities and the type 0 string theory within M-theory.

Findings

Exact solvability of models in magnetic flux backgrounds

Identification of tachyonic instabilities in these models

Proposal of M-theory description for type 0B theory

Abstract

Models of closed superstrings in certain curved NS-NS magnetic flux backgrounds are exactly solvable in terms of free fields. They interpolate between free superstring theories with periodic and antiperiodic boundary conditions for fermions around some compact direction, and, in particular, between type 0 and type II string theories. Using ``9-11 flip'', this interpolation can be extended to M-theory and provides an interesting setting for a study of tachyon problem in closed string theory. Starting with a general 2-parameter family of such Melvin-type models, we present several new magnetic flux backgrounds in 10-d string theory and 11-d M-theory and discuss their tachyonic instabilities. In particular, we suggest a description of type 0B theory in terms of M-theory in curved magnetic flux background, which supports its conjectured SL(2,Z) symmetry, and in which the type 0 tachyon appears to correspond to a state in 11-d supergravity multiplet. In another ``T-dual'' description, the tachyon is related to a winding membrane state.