Paper detail

False vacuum energy dominated inflation with large $r$ and the importance of $κ_s$

We investigate to which extent and under which circumstances false vacuum energy ($V_0$) dominated slow-roll inflation is compatible with a large tensor-to-scalar ratio $r = O(0.1)$, as indicated by the recent BICEP2 measurement. With $V_0$ we refer to a constant contribution to the inflaton potential, present before a phase transition takes place and absent in the true vacuum of the theory, like e.g. in hybrid inflation. Based on model-independent considerations, we derive an upper bound on the possible amount of $V_0$ domination and highlight the importance of higher-order runnings of the scalar spectral index (beyond $α_s$) in order to realise scenarios of $V_0$ dominated inflation. We study the conditions for $V_0$ domination explicitly with an inflaton potential reconstruction around the inflaton field value 50 e-folds before the end of inflation, taking into account the present observational data. To this end, we provide the up-to-date parameter constraints within $Λ$CDM + $r$ + $α_s$ + $κ_s$ using the cosmological parameter estimation code Monte Python together with the Boltzmann code CLASS.