Gravitino dark matter from Q-ball decays

TL;DR

This paper explores how Q-ball decays in the early universe can produce gravitino dark matter, potentially explaining the observed baryon-to-dark-matter ratio and affecting small-scale cosmic structures.

Contribution

It demonstrates that gravitino dark matter from Q-ball decay is consistent with observations and can account for the baryon-to-dark-matter ratio across various models.

Findings

Gravitinos around 1 GeV fit observational bounds.

Q-ball decay can dominate gravitino production at low reheat temperatures.

Light gravitinos (50 eV - 100 keV) can serve as warm dark matter affecting small-scale structures.

Abstract

Affleck-Dine baryogenesis, accompanied by the formation and subsequent decay of Q-balls, can generate both the baryon asymmetry of the universe and dark matter in the form of gravitinos. The gravitinos from Q-ball decay dominate over the thermally produced population if the reheat temperature is less than 10^7 GeV. We show that a gravitino with mass around 1 GeV is consistent with all observational bounds and can explain the baryon-to-dark-matter ratio in the gauge-mediated models of supersymmetry breaking for a wide range of cosmological and Q-ball parameters. Moreover, decaying Q-balls can be the dominant production mechanism for m_{3/2} < 1 GeV gravitinos if the Q-balls are formed from a (B-L) = 0 condensate, which produces no net baryon asymmetry. Gravitinos with masses in the range (50 eV - 100 keV) produced in this way can act as warm dark matter and can have observable imprint on the small-scale structure.