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arXiv · 1309.4782

Can non-local or higher derivative theories provide alternatives to inflation?

Ghazal Geshnizjani·Nahid Ahmadi
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Abstract

The standard mechanism for producing the observed scale-invariant power spectrum from adiabatic vacuum fluctuations relies on first order derivative of fields in the action for curvature perturbations. It has been proven \cite{Geshnizjani:2011dk} that, under this ansatz, any theory of early universe that matches cosmological observations should include a phase of accelerated expansion (i.e. inflation) or it has to break at least one of the following tenets of classical general relativity: Null Energy Conditions (NEC), subluminal signal propagation, or sub-Planckian energy densities. We extend this proof to a large class of theories with higher (spatial) derivative or non-local terms in the action. Interestingly, only theories in the neighborhood of Lifshitz points with $ω_k \propto k^0$ and $k^3$ remain viable.

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Ghazal Geshnizjani, Nahid Ahmadi. 2013-12-09. Can non-local or higher derivative theories provide alternatives to inflation?. https://doi.org/10.1088/1475-7516%2F2013%2F11%2F029

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