Open string decoupling and tachyon condensation

TL;DR

This paper investigates how open string modes decouple at tachyon potential minima and explores the emergence of closed string sectors through tachyon condensation, revealing insights into non-perturbative string dynamics.

Contribution

It demonstrates open string decoupling at tachyon minima using boundary state formalism and clarifies the generation of closed strings during tachyon condensation.

Findings

Open string modes decouple at tachyon minima.

Closed string sector emerges from open string condensation.

Coupling constants become independent at the minima.

Abstract

The amplitudes in perturbative open string theory are examined as functions of the tachyon condensate parameter. The boundary state formalism demonstrates the decoupling of the open string modes at the non-perturbative minima of the tachyon potential via a degeneration of open world-sheets and identifies an independence of the coupling constants $g_s$ and $g_{YM}$ at general values of the tachyon condensate. The closed sector is generated at the quantum level; it is also generated at the classical level through the condensation of the propagating open string modes on the D-brane degrees of freedom.