BPS Limit of Multi- D- and DF-strings in Boundary String Field Theory

TL;DR

This paper derives a BPS limit for multi D- and DF-strings in boundary superstring field theory, revealing exact relations and charge distributions in the thin-string limit, and providing insights into their static solutions and energy configurations.

Contribution

It systematically establishes the BPS limit for multi D- and DF-strings, including the derivation of the BPS sum rule and the exact charge-energy distribution relations.

Findings

BPS limit obtained in the thin-string regime.

BPS sum rule fulfilled with Gaussian tachyon potential.

Fundamental string charge density matches energy density in DF-strings.

Abstract

A BPS limit is systematically derived for straight multi- D- and DF-strings from the D3D3bar system in the context of boundary superstring field theory. The BPS limit is obtained in the limit of thin D(F)-strings, where the Bogomolnyi equation supports singular static multi-D(F)-string solutions. For the BPS multi-string configurations with arbitrary separations, BPS sum rule is fulfilled under a Gaussian type tachyon potential and reproduces exactly the descent relation. For the DF-strings ((p,q)-strings), the distribution of fundamental string charge density coincides with its energy density and the Hamiltonian density takes the BPS formula of square-root form.