Kinetic and chemical equilibrium of the Universe and gravitino production

TL;DR

This paper investigates how flat directions in supersymmetric theories affect the Universe's thermal history and gravitino production, showing that delayed thermalization can resolve the gravitino problem.

Contribution

It provides a detailed calculation of gravitino production considering non-thermal conditions and phase space suppression effects in a novel supersymmetric scenario.

Findings

Gravitino abundance remains within cosmological limits.

Delayed thermalization due to flat directions impacts gravitino production.

Phase space suppression reduces gravitino yield in heavy gauge boson scenarios.

Abstract

Flat directions in generic supersymmetric theories can change the thermal history of the Universe. A novel scenario was proposed earlier where the vacuum expectation value of the flat directions induces large masses for all the gauge bosons and gauginos. This delays the thermalization of the Universe after inflation and solves the gravitino problem. In this article we perform a detailed calculation of the above scenario. We include the appropriate initial state particle distribution functions, consider the conditions for the feasibility of the non-thermal scenario, and investigate phase space suppression of gravitino production in the context of heavy gauge bosons and gauginos in the final state. We find that the total gravitino abundance generated is consistent with cosmological constraints.