String Fluid from Unstable D-branes

TL;DR

This paper analyzes the classical dynamics of unstable D-branes using Sen's effective action, revealing a string fluid behavior in the true vacuum and establishing a dual Lagrangian linked to Nielsen-Olesen string theory.

Contribution

It provides an exact classical analysis of unstable D-branes, demonstrating a relativistic string fluid description and deriving a dual Lagrangian with a key constraint.

Findings

Hamiltonian dynamics remains well-defined in the true vacuum

Energy density equals flux density in co-moving frame

A finite dual Lagrangian relates to Nielsen-Olesen string theory

Abstract

We consider Sen's effective action for unstable D-branes, and study its classical dynamics exactly. In the true vacuum, the Hamiltonian dynamics remains well-defined despite a vanishing action, and is that of massive relativistic string fluid of freely moving electric flux lines. The energy(tension) density equals the flux density in the local co-moving frame. Furthermore, a finite dual Lagrangian exists and is related to the Nielsen-Olesen field theory of ``dual'' strings, supplemented by a crucial constraint. We conclude with discussion on the endpoint of tachyon condensation.