Alternatives to Inflation – Non-Minimal Ekpyrosis & Conflation


Fertig, A. (2015). Alternatives to Inflation – Non-Minimal Ekpyrosis & Conflation . Perimeter Institute. https://pirsa.org/15120027


Fertig, Angelika. Alternatives to Inflation – Non-Minimal Ekpyrosis & Conflation . Perimeter Institute, Dec. 15, 2015, https://pirsa.org/15120027


          @misc{ pirsa_15120027,
            doi = {10.48660/15120027},
            url = {https://pirsa.org/15120027},
            author = {Fertig, Angelika},
            keywords = {Cosmology},
            language = {en},
            title = {Alternatives to Inflation {\textendash}  Non-Minimal Ekpyrosis \& Conflation    },
            publisher = {Perimeter Institute},
            year = {2015},
            month = {dec},
            note = {PIRSA:15120027 see, \url{https://pirsa.org}}


In this talk I derive the evolution equations for two scalar fields with non-canonical field space metric up to third order in perturbation theory, employing the covariant formalism. These equations can be used to calculate the local bi- and trispectra of the non-minimal ekpyrotic model. Remarkably, the nearly scale-invariant entropy perturbations have vanishing bi- and trispectra during the ekpyrotic phase. However, an efficient conversion process to curvature perturbations induces local non-Gaussianity parameters f_NL and g_NL at levels that should be detectable by near-future observations.
In the second part of the talk I construct a new kind of cosmological model – conflation. The universe undergoes accelerated expansion, but with crucial differences compared to ordinary inflation. In particular, the potential energy is negative, which is of interest for supergravity and string theory where both negative potentials and the required scalar-tensor couplings are rather natural. A distinguishing feature of the model is that it does not amplify adiabatic scalar and tensor fluctuations, and in particular does not lead to eternal inflation and the associated infinities.