Graviton production from D-string recombination and annihilation

TL;DR

This paper investigates graviton production from D-string processes in the early Universe, finding that recombination is weak but annihilation could produce detectable gravitational modes from decay of massive remnants.

Contribution

It introduces the analysis of graviton production via D-string annihilation and decay, highlighting potential observable gravitational signatures.

Findings

D-string recombination is too weak to produce significant gravitons.

D-string annihilation results in massive remnants that decay into gravitational modes.

Potential for observable gravitational signals from stable massive modes.

Abstract

Fundamental superstrings (F-strings) and D-strings may be produced at high temperature in the early Universe. Assuming that, we investigate if any of the instabilities present in systems of strings and branes can give rise to a phenomenologically interesting production of gravitons. We focus on D-strings and find that D-string recombination is a far too weak process for both astrophysical and cosmological sources. On the other hand if D-strings annihilate they mostly produce massive closed string remnants and a characteristic spectrum of gravitational modes is produced by the remnant decay, which may be phenomenologically interesting in the case these gravitational modes are massive and stable.