D-strings and F-strings from string loops

TL;DR

This paper explores how string loop effects can explain the emergence of background fields in string theory, supporting the duality between D-strings and F-strings through theoretical arguments and specific models.

Contribution

It proposes a string loop-based explanation for background fields and provides a rigorous justification for the SL(2,Z) duality between D-strings and F-strings in type IIB theory.

Findings

String loop effects can account for background fields in string theory.

The SL(2,Z) duality between D-strings and F-strings is supported by the arguments.

The paper discusses the relation between type IIA and 11-dimensional membranes.

Abstract

Since the background fields of the string low energy action are supposed to be the long range manifestation of a condensate of strings, the addition of world sheet actions to the low energy effective action needs some string theoretic explanation. In this paper we suggest that this may be understood, as being due to string loop effects. We first present arguments using an equation due to Tseytlin and then more rigorously in the particular case of type IIB theory by invoking the Fischler-Susskind effect. The argument provides further justification for ${\rm SL}(2,Z)$ duality between D-strings and F(fundamental)-strings. In an appendix we comment on recent attempts to relate the type IIA membrane to the 11-dimensional membrane.