Avoided Deconfinement in Randall-Sundrum Models

Abstract: We study first order phase transitions in Randall-Sundrum models in the early universe dual to confinement in large-$N$ gauge theories. The transition rate to the confined phase is suppressed by a factor $\exp(-N^2)$, and may not complete for $N \gg 1$, instead leading to an eternally inflating phase. To avoid this fate, the resulting constraint on $N$ makes the RS effective field theory only marginally under control. We present a mechanism where the IR brane remains stabilized at very high temperature, so that the theory stays in the confined phase at all times after inflation and reheating. We call this mechanism avoided deconfinement. The mechanism involves adding new scalar fields on the IR brane which provide a stablilizing contribution to the radion potential at finite temperature, in a spirit similar to Weinberg's symmetry non-restoration mechanism. Avoided deconfinement allows for a viable cosmology for theories with parametrically large $N$. Early universe cosmological phenomena such as WIMP freeze-out, axion abundance, baryogenesis, phase transitions, and gravitational wave signatures are qualitatively modified.