String Motion in Fivebrane Geometry

TL;DR

This paper analyzes the classical motion of a test string in heterotic fivebrane backgrounds, revealing unique orbital behaviors and long-distance inverse cubic law deviations that could test string theory effects.

Contribution

It provides a detailed analysis of string trajectories in fivebrane geometries, including singular cases and the impact of instanton size, highlighting novel orbital dynamics.

Findings

Orbits are circular or open, analogous to electron-monopole systems.

At long distances, the geometry obeys an inverse cubic law.

Potential for experimental tests of stringy effects if fivebranes exist.

Abstract

The classical motion of a test string in the transverse space of two types of heterotic fivebrane sources is fully analyzed, for arbitrary instanton scale size. The singular case is treated as a special case and does not arise in the continuous limit of zero instanton size. We find that the orbits are either circular or open, which is a solitonic analogy with the motion of an electron around a magnetic monopole, although the system we consider is quantitatively different. We emphasize that at long distance this geometry does not satisfy the inverse square law, but satisfies the inverse cubic law. If the fivebrane exists in nature and this structure survives after any proper compactification, this last result can be used to test classical ``stringy'' effects.