Reheating constraints to inflationary models

Liang Dai; Marc Kamionkowski; Junpu Wang

doi:10.1103/PhysRevLett.113.041302

paper

Reheating constraints to inflationary models

arXiv:1404.6704 · doi:10.1103/PhysRevLett.113.041302

Abstract

Evidence from the BICEP2 experiment for a significant gravitational-wave background has focussed attention on inflaton potentials $V (ϕ) \propto ϕ^{α}$ with $α = 2$ ("chaotic" or " $m^{2} ϕ^{2}$ " inflation) or with smaller values of $α$ , as may arise in axion-monodromy models. Here we show that reheating considerations may provide additional constraints to these models. The reheating phase preceding the radiation era is modeled by an effective equation-of-state parameter $w_{re}$ . The canonical reheating scenario is then described by $w_{re} = 0$ . The simplest $α = 2$ models are consistent with $w_{re} = 0$ for values of $n_{s}$ well within the current $1 σ$ range. Models with $α = 1$ or $α = 2/3$ require a more exotic reheating phase, with $- 1/3 < w_{re} < 0$ , unless $n_{s}$ falls above the current $1 σ$ range. Likewise, models with $α = 4$ require a physically implausible $w_{re} > 1/3$ , unless $n_{s}$ is close to the lower limit of the $2 σ$ range. For $m^{2} ϕ^{2}$ inflation and canonical reheating as a benchmark, we derive a relation $lo g_{10} (T_{re} /1 0^{6} GeV) ≃ 2000 (n_{s} - 0.96)$ between the reheat temperature $T_{re}$ and the scalar spectral index $n_{s}$ . Thus, if $n_{s}$ is close to its central value, then $T_{re} ≲ 1 0^{6}$ ~GeV, just above the electroweak scale. If the reheat temperature is higher, as many theorists may prefer, then the scalar spectral index should be closer to $n_{s} ≃ 0.965$ (at the pivot scale $k = 0.05 Mpc^{- 1}$ ), near the upper limit of the $1 σ$ error range. Improved precision in the measurement of $n_{s}$ should allow $m^{2} ϕ^{2}$ , axion-monodromy, and $ϕ^{4}$ models to be distinguished, even without precise measurement of $r$ , and to test the $m^{2} ϕ^{2}$ expectation of $n_{s} ≃ 0.965$ .

arXiv comment5 pages, 5 figures. Revised version clarifies the dependence of the result on the pivot scale

Reheating constraints to inflationary models

Abstract

References in corpus (31)

Cited by in corpus (200)