Scale independent spin effects in D-brane dynamics

TL;DR

This paper investigates spin interactions between moving D-branes, revealing scale-invariant effects governed by zero modes, and provides a field theory interpretation including gyromagnetic ratio and quadrupole moment for D0-branes.

Contribution

It introduces a detailed analysis of spin effects in D-brane dynamics, highlighting their scale invariance and providing new field theory insights into D0-brane properties.

Findings

Spin effects are scale-invariant and dominated by zero modes.

The gyromagnetic ratio for D0-branes is g=1.

D0-branes possess a quadrupole moment.

Abstract

We study spin interactions between two moving D-branes using the Green-Schwarz formalism of boundary states. We focus our attention on the leading terms for small velocities v, of the form v^{4-n}/r^{7-p+n} (v^{2-n}/r^{3-p+n}) for p-p (p-p+4) systems, with 16 (8) supercharges. In analogy with standard G-S computations of massless four-point one-loop amplitudes in Type I theory, the above terms are governed purely by zero modes, massive states contributions cancelling as expected by the residual supersymmetry. This implies the scale invariance of these leading spin-effects, supporting the relevant matrix model descriptions of supergravity interactions; in this context, we also discuss similar results for more general brane configurations. We then give a field theory interpretation of our results, that allows in particular to deduce the gyromagnetic ratio g=1 and the presence of a quadrupole moment for D0-branes.