Fundamental Strings in Open String Theory at the Tachyonic Vacuum

TL;DR

This work shows that the tachyonic vacuum of a D-$p$-brane hosts solitonic string solutions whose dynamics are governed by the $S_{NG}$ in $(25+1)$ dimensions, providing strong evidence that full $(25+1)$-D Poincare invariance is restored at the vacuum. It provides a concrete mapping from Nambu-Goto strings in $(25+1)$D to energy-localized solitons on the brane world-volume and explains how flux quantization fixes the fundamental string tension. The paper further argues that open string field theory at the tachyon vacuum must contain closed string excitations, with mechanisms for winding and momentum modes connected by T-duality, thereby supporting a non-perturbative, closed-string-inclusive picture of string theory from open string data.

Abstract

We show that the world-volume theory on a D-p-brane at the tachyonic vacuum has solitonic string solutions whose dynamics is governed by the Nambu-Goto action of a string moving in (25+1) dimensional space-time. This provides strong evidence for the conjecture that at this vacuum the full (25+1) dimensional Poincare invariance is restored. We also use this result to argue that the open string field theory at the tachyonic vacuum must contain closed string excitations.