The Gravitational Field of String Matter

TL;DR

This paper investigates the gravitational deflection of particles by string-based matter configurations, revealing smaller deflection angles than classical predictions and deriving exact solutions for the associated spacetime metrics.

Contribution

It provides a perturbative and exact analysis of the gravitational field of string matter, highlighting differences from general relativity and exploring the role of superstring fields.

Findings

Deflection angles are smaller than in general relativity.

Exact solutions for string star metrics without horizons.

Superstring fields influence scattering contributions.

Abstract

We study the scattering of a massless and neutral test particle in the gravitational field of a body (the string star) made of a large number of scalar states of the superstring. We consider two cases, the one in which these states are neutral string excitations massive already in ten dimensions and the one in which their masses (and charges) originate in the process of compactification on tori. A perturbative calculation based on superstring amplitudes gives us the deflection angle up to the second order in Newton's constant. A comparison with field theory explicitly shows which among the various massless fields of the superstring give a contribution to the scattering process. In both cases, the deflection angle is smaller than the one computed in general relativity. The perturbative series can be resummed by finding the exact solution to the classical equations of motion of the corresponding low-energy action. The space-time metric of our two examples of string stars has no horizon.