Origin of the geometric tachyon

TL;DR

This paper investigates how the background of NS5-branes influences Dp-brane dynamics, revealing that proper acceleration caused by the dilaton field induces a tachyonic instability resembling an inverted harmonic oscillator.

Contribution

It demonstrates that the proper acceleration in the NS5-brane background modifies Dp-brane motion, leading to a geometric origin of the tachyonic instability.

Findings

Proper acceleration affects Dp-brane dynamics near NS5-branes.

The radial mode behaves like an inverted harmonic oscillator.

This acceleration explains the geometric origin of the tachyon.

Abstract

The motion of a Dp-brane in the background of a stack of coincident NS5-branes is analysed as the motion of a relativistic point particle in the transverse space of the five-branes. In this system, the particle experiences a proper acceleration orthogonal to its proper velocity due to the background dilaton field which changes the dynamics from that of a simple geodesic motion. In particular, we show that in the vicinity of the five-branes, it is this acceleration which is responsible for modifying the motion of the radial mode to that of an inverted simple harmonic oscillator leading to the tachyonic instability.