Warped reheating in multi-throat brane inflation

Abstract

We investigate in some quantitative details the viability of reheating in multi-throat brane inflationary scenarios by estimating and comparing the time scales for the various processes involved. We also calculate within perturbative string theory the decay rate of excited closed strings into KK modes and compare with that of their decay into gravitons; we find that in the inflationary throat the former is preferred. We also find that over a small but reasonable range of parameters of the background geometry, these KK modes will preferably tunnel to another throat (possibly containing the Standard Model) instead of decaying to gravitons due largely to their suppressed coupling to the bulk gravitons. Once tunneled, the same suppressed coupling to the gravitons again allows them to reheat the Standard Model efficiently. We also consider the effects of adding more throats to the system and find that for extra throats with small warping, reheating still seems viable.

Kähler moduli inflation

“…If the standard model lies elsewhere, the inflaton will couple to standard model fields through higher dimension operators and a more detailed analysis is required. (For a recent analysis of reheating in brane-antibrane inflation see [32]). …”

Inflation and String Theory

“…When the inflationary energy is also localized on a brane, one can take a modular approach, in which the inflationary sector and the visible sector constructed separately, in local geometries approximating regions of some unspecified compactification, and their interactions are then computed or parameterized. This strategy has been fruitful in extensive explorations [545][546][547][548][549][550][551][552][553][554][555][556] in the context of warped D-brane inflation [41], as we review in §5.1. Reheating in other models involving D-branes has been studied in e.g.…”

“…The reheating stage of warped D-brane inflation was carefully examined in [545,546,548,551,553], revealing a complex cascade of energy from the inflaton to the visible sector and to invisible relics. To set the stage, we remark that a modular approach to reheating is very natural in this context: because the inflaton sector involves a D3-brane in a local geometry, it is reasonable to identify the warped throat where inflation occurs as one module, and to situate the Standard Model on D-branes in a different region of the geometry, either in another warped throat or in the unwarped bulk region.…”

“…On the other hand, their couplings to Kaluza-Klein zero modes, including the graviton, are suppressed by M pl . The warping creates a gravitational potential barrier that confines massive particles to the infrared region: access to other throats is via tunnelling 11 through the bulk of the compactification, which is very slow compared to perturbative decays [545,546,548,550,649]. As a result, the characteristic timescales typically obey τ therm τ graviton τ tunnel , (5.70) where τ therm denotes the thermalization time for Kaluza-Klein modes of the inflationary throat, τ graviton is the timescale for decay to gravitons, and τ tunnel is the tunnelling timescale.…”

Stringy effects during inflation and reheating

“…Therefore, this decay should occur at the local string time scale ' inf and should result in KK gravitons localized in the inflationary throat. The next step is then the transfer of these gravitons to the SM throat by tunneling, as has been discussed in [56]-see related discussion in [57,58].…”