Gauge singlet scalar as inflaton and thermal relic dark matter

We show that, by adding a gauge singlet scalar S to the standard model which is nonminimally coupled to gravity, S can act both as the inflaton and as thermal relic dark matter. We obtain the allowed region of the (mₛ,mₕ) parameter space which gives a spectral index in agreement with observational bounds and also produces the observed dark matter density while not violating vacuum stability or nonperturbativity constraints. We show that, in contrast to the case of Higgs inflation, once quantum corrections are included the spectral index is significantly larger than the classical value ($n=0.966$ for $N=60$) for all allowed values of the Higgs mass mₕ. The range of Higgs mass compatible with the constraints is 145 GeVmₕ170 GeV. The S mass lies in the range 45 GeVmₛ1 TeV for the case of a real S scalar with large quartic self-coupling λₛ, with a smaller upper bound for smaller λₛ. A region of the parameter space is accessible to direct searches at the LHC via h→SS, while future direct dark matter searches should be able to significantly constrain the model.