Identifying the curvaton within MSSM

TL;DR

The paper addresses how MSSM flat directions can act as curvatons by analyzing inflaton couplings and the thermal history after inflation. It shows that thermal corrections and SUSY-breaking $A$-terms substantially modify curvaton dynamics, selecting the ${\bf udd}$ direction as a viable MSSM curvaton that can start oscillating early and eventually dominate the energy density before decay. The udd condensate can convert its isocurvature perturbations into adiabatic curvature perturbations, potentially produce observable CMB fluctuations, and even generate dark matter via $Q$-ball evaporation. The work demonstrates that accounting for thermal effects in MSSM curvatons resolves previous obstacles and provides a concrete, testable link between early-universe cosmology and MSSM physics.

Abstract

We consider inflaton couplings to MSSM flat directions and the thermalization of the inflaton decay products, taking into account gauge symmetry breaking due to flat direction condensates. We then search for a suitable curvaton candidate among the flat directions, requiring an early thermally induced start for the flat direction oscillations to facilitate the necessary curvaton energy density dominance. We demonstrate that the supersymmetry breaking $A$-term is crucial for achieving a successful curvaton scenario. Among the many possible candidates, we identify the ${\bf u_1dd}$ flat direction as a viable MSSM curvaton.