A New Action for Superstring Field Theory

TL;DR

This paper introduces a new background-independent superstring field theory action that maintains the same physical amplitudes as Sen's theory but exhibits standard diffeomorphism invariance and a shift symmetry, improving theoretical consistency.

Contribution

A novel superstring field theory action is proposed that is background independent and preserves physical amplitudes, addressing key limitations of Sen's original formulation.

Findings

The new action reduces to Sen's action in a certain limit.

It exhibits background independence and diffeomorphism invariance.

It describes two superstrings with separate self-interactions, each with a graviton.

Abstract

Sen's superstring field theory successfully formulates perturbative superstring theory but has a number of unusual features. The action is not background independent and the resulting effective field theory does not appear to have standard diffeomorphsim symmetry - instead there is an exotic gauge symmetry that acts on some fields but not others. A new action is found that reduces to Sen's action in a certain limit and gives the same results as Sen's theory for physical superstring amplitudes. However, the new theory is background independent: there is a shift symmetry so that a change in the background can be compensated for by a corresponding shift in the string fields. Sen's theory has two string fields leading to the physical interacting superstring plus a free superstring that decouples from the physical superstring. The new terms in the action give self-interactions to the second superstring which remains decoupled from the physical superstring. The two superstrings each have a graviton and the effective action for the two gravitons coupled to a background metric is studied and shown to be background independent and diffeomorphism invariant, and the origin of further diffeomorphism-like symmetries is explained.