BPS Nature of 3-String Junctions

TL;DR

This paper investigates BPS-saturated solutions representing 3-string junctions on D-strings, confirming their stability and tension balance through explicit angle calculations and supporting Schwarz's conjecture.

Contribution

It provides a detailed analysis of classical BPS solutions for 3-string junctions on D-strings, validating their BPS nature and tension balance.

Findings

Angles of junctions computed and match BPS conditions

Vector sum of tensions confirmed to be zero

Supports Schwarz's conjecture on BPS states

Abstract

We study BPS-saturated classical solutions for the world-sheet theory of a D-string in the presence of a point charge. These solutions are interpreted as describing planar 3-string junctions, which arise because the original D-string is deformed by the presence of the inserted charge. We compute the angles of the junctions and show that the vector sum of string tensions is zero, confirming a conjecture of Schwarz that such configurations are BPS states.