Closed Superstrings in Magnetic Field: Instabilities and Supersymmetry Breaking

Abstract

We consider a 2-parameter class of solvable closed superstring models which ‘interpolate’ between Kaluza-Klein and dilatonic Melvin magnetic flux tube backgrounds. The spectrum of string states has similarities with the Landau spectrum for a charged particle in a uniform magnetic field. The presence of spin-dependent ‘gyromagnetic’ interaction implies breaking of supersymmetry and possible existence of tachyonic instabilities (for certain values of magnetic parameters). We study in detail the simplest example of the Kaluza-Klein Melvin model describing superstring moving in a flat but non-trivial 10-dimensional space containing a 3d factor which is a ‘twisted’ product of a 2-plane and an internal circle. We also discuss the compact version of this model constructed by ‘twisting’ the product of SU(2) and U(1) in SU(2) × U(1) WZNW theory without changing the local group-space geometry (and the central charge). We explain how the supersymmetry is broken by continuous ‘magnetic’ twist parameters and comment on possible implications for internal space compactification models.KeywordsPartition FunctionOpen StringSupersymmetry BreakingClosed StringMagnetic Flux TubeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.