Testing string theory via black hole space-times

TL;DR

This paper compares charged black holes in string theory and general relativity, proposing experiments involving gyromagnetic ratios and light propagation to distinguish between the theories and test stringy effects.

Contribution

It provides new theoretical predictions for observable differences in black hole properties in string theory versus general relativity, including gyromagnetic ratios and electromagnetic damping effects.

Findings

Different gyromagnetic ratios in Einstein and String frames.

Predicted electromagnetic damping in star-black hole systems.

Potential experimental tests for string theory effects.

Abstract

Charged black holes, both spherically symmetric and rotating, in the low energy limit of string theory (Einstein-Maxwell-dilaton theory) are compared to analogous geometries in pure general relativity. We describe various physical differences and investigate some experiments which can distinguish between the two theories. In particular we discuss the gyro-magnetic ratios of rotating black holes and the propagation of light on black hole backgrounds. For the former we obtain an expression in the Einstein frame (EF) which is different from the one in the String frame (SF). This (and other results) can be used to test the stringy nature of matter. For a binary system consisting of a star and a rotating black hole, we give estimates of the damping of electro-magnetic radiation coming from the star due to the existence of a scalar component of gravity.