A Note on Marginally Stable Bound States in Type II String Theory

TL;DR

This paper investigates marginally stable bound states in type II string theory, proposing a test for their existence and confirming their spectrum aligns with U-duality predictions using recent theoretical results.

Contribution

It introduces a test for marginally stable bound states in type II string theory and confirms their spectrum matches U-duality predictions.

Findings

Spectrum of bound states agrees with U-duality predictions

Proposed test supports existence of marginally stable states

Recent results of Polchinski and Witten validate the spectrum

Abstract

Spectrum of elementary string states in type II string theory contains ultra-short multiplets that are marginally stable. $U$-duality transformation converts these states into bound states at threshold of $p$-branes carrying Ramond-Ramond charges, and wrapped around $p$-cycles of a torus. We propose a test for the existence of these marginally stable bound states. Using the recent results of Polchinski and of Witten, we argue that the spectrum of bound states of $p$-branes is in agreement with the prediction of $U$-duality.