Reheating from Tachyon Condensation

TL;DR

The paper investigates reheating after D-brane inflation via tachyon condensation, proposing that a time-dependent tachyon background $T(t,\mathbf{x})$ couples to massless gauge fields and can convert the energy of the rolling tachyon into radiation. It analyzes a simplified, kink-based tachyon background and solves gauge-field dynamics region by region, using matching conditions and a lattice discretization to obtain Bogoliubov coefficients that determine particle production. The results show that, with a large enough extra dimension $L$, a steep kink slope $q$, and a smoothing scale $\Lambda$, the produced radiation density $\rho_r$ can reach or exceed a critical threshold $\rho_c$, enabling efficient reheating and a transition to a radiation-dominated era. This supports the viability of reheating in brane-antibrane inflation scenarios where the standard model resides on a descendant brane, though it relies on simplifying assumptions that warrant further numerical and analytical refinement.

Abstract

We argue that it may be possible to reheat the universe after inflation driven by D-brane annihilation, due to the coupling of massless fields to the time-dependent tachyon condensate which describes the annihilation process. This mechanism can work if the original branes annihilate to a stable brane containing the standard model. Given reasonable assumptions about the shape of the tachyon background configuration and the size of the relevant extra dimension, the reheating can be efficient enough to overcome the problem of the universe being perpetually dominated by cold dark tachyon matter. In particular, reheating is most efficient when the final brane codimension is large, and when the derivatives of the tachyon background are large.