The Heterotic Life of the D-particle

TL;DR

This work develops a quantum-mechanical model for D0-branes in the presence of type I' orientifolds and D8-branes and links the results to the heterotic string via dualities. It demonstrates that eight D8-branes per orientifold cancel linear potentials, yielding leading interactions $V \sim v^2/r^3$ for transverse scattering and $V \sim v^4/r^7$ for parallel scattering, consistent with supergravity and previous D-particle analyses. The study also shows that eleven-dimensional Planck-length dynamics, via $l_{11}$, governs the system and that dualities map these D-particle interactions to nine-dimensional heterotic black holes, including non-BPS bound-state possibilities tied to membranes. Overall, the paper connects I' D-particle quantum mechanics, D-brane cancellations, and heterotic/M-theory physics, highlighting sub-stringy length scales and potential non-perturbative bound states.

Abstract

We study the dynamics of D-particles (D0-branes) in type I' string theory and of the corresponding states in the dual heterotic description. We account for the presence of the two 8-orientifolds (8 dimensional orientifold planes) and sixteen D8-branes by deriving the appropriate quantum mechanical system. We recover the familiar condition of eight D8-branes for each 8-orientifold. We investigate bound states and compute the phase shifts for the scattering of such states and find that they agree with the expectations from the supergravity action. In the type I' regime we study the motion transverse to the 8-orientifold and find an interesting cancellation effect.