We show that , by adding a gauge singlet scalar S to the Standard Model which is non-minimally coupled to gravity , S can act both as the inflaton and as thermal relic dark matter .
We obtain the allowed region of the ( m _ { s } ,~ { } m _ { h } ) 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 non-perturbativity 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 m _ { h } .
The range of Higgs mass compatible with the constraints is 145 { GeV } \lesssim m _ { h } \lesssim 170 GeV .
The S mass lies in the range 45 { GeV } \lesssim m _ { s } \lesssim 1 TeV for the case of a real S scalar with large quartic self-coupling \lambda _ { s } , with a smaller upper bound for smaller \lambda _ { s } .
A region of the parameter space is accessible to direct searches at the LHC via h \rightarrow SS , while future direct dark matter searches should be able to significantly constrain the model .