Quantum effects in gravitational wave signals from cuspy superstrings

Abstract

We study the gravitational emission, in superstring theory, from fundamental stringsexhibiting cusps. The classical computation of the gravitational radiation signal from cuspystrings features strong bursts in the special null directions associated with the cusps. Weperform a quantum computation of the gravitational radiation signal from a cuspy string,as measured in a gravitational wave detector using matched filtering and locatedin the special null direction associated with the cusp. We study the quantumstatistics (expectation value and variance) of the measured filtered signal and findthat it is very sharply peaked around the classical prediction. Ultimately, thisresult follows from the fact that the detector is a low-pass filter which is blind tothe violent high-frequency quantum fluctuations of both the string worldsheetXμ(τ,σ) and the incominggravitational field hμνin(x).