Orbifolds as Melvin Geometry

TL;DR

This paper demonstrates that various noncompact abelian orbifolds can be realized as limits of parameters in Melvin backgrounds, revealing connections between different string theories and providing insights into background decay and tachyon condensation.

Contribution

It explicitly shows the realization of orbifolds as limits of Melvin backgrounds and establishes dualities between type II and type 0 string theories through marginal deformations.

Findings

Orbifolds are special limits of Melvin backgrounds.

Supersymmetric and nonsupersymmetric orbifolds are connected via marginal deformation.

Includes discussion on decay of unstable backgrounds and closed string tachyons.

Abstract

In this paper we explicitly show that the various noncompact abelian orbifolds are realized as special limits of parameters in type II (NSNS) Melvin background and its higher dimensional generalizations. As a result the supersymmetric ALE spaces (A-type C^2/Z_N) and nonsupersymmetric orbifolds in type II and type 0 theory are all connected with each other by the exactly marginal deformation. Our results provide new examples of the duality between type II and type 0 string theory. We also discuss the decay of unstable backgrounds in this model which include closed string tachyons.