Some Exact Results on Tachyon Condensation in String Field Theory

TL;DR

This paper introduces a natural coordinate system in string field theory that simplifies the analysis of open string tachyon condensation, allowing exact calculations of D-brane tensions and profiles.

Contribution

It proposes a coordinate system based on the worldsheet renormalization group that isolates the tachyon field, enabling exact results in tachyon condensation and D-brane physics.

Findings

Tension of the D25-brane is canceled by tachyon condensation.

Exact profiles and tensions of lower-dimensional D-branes are computed.

The coordinate system simplifies the study of D-branes as solitons.

Abstract

The study of open string tachyon condensation in string field theory can be drastically simplified by making an appropriate choice of coordinates on the space of string fields. We show that a very natural coordinate system is suggested by the connection between the worldsheet renormalization group and spacetime physics. In this system only one field, the tachyon, condenses while all other fields have vanishing expectation values. These coordinates are also well-suited to the study of D-branes as solitons. We use them to show that the tension of the D25-brane is cancelled by tachyon condensation and compute exactly the profiles and tensions of lower dimensional D-branes.