Disformal Inflation

Nemanja Kaloper

doi:10.1016/j.physletb.2004.01.005

paper

Disformal Inflation

arXiv:hep-ph/0312002 · doi:10.1016/j.physletb.2004.01.005

Abstract

We show how short inflation naturally arises in a non-minimal gravity theory with a scalar field without any potential terms. This field drives inflation solely by its derivatives, which couple to the matter only through the combination $g ˉ_{μν} = g_{μν} - \frac{1}{m ^{4}} \partial_{μ} ϕ \partial_{ν} ϕ$ . The theory is free of instabilities around the usual Minkowski vacuum. Inflation lasts as long as $ϕ ˙^{2} > m^{4}$ , and terminates gracefully once the scalar field kinetic energy drops below $m^{4}$ . The total number of e-folds is given by the initial inflaton energy $ϕ ˙_{0}^{2}$ as $N ≃ \frac{1}{3} ln (\frac{ϕ ˙ _{0}}{m ^{2}})$ . The field $ϕ$ can neither efficiently reheat the universe nor produce the primordial density fluctuations. However this could be remedied by invoking the curvaton mechanism. If inflation starts when $ϕ ˙_{0}^{2} \sim M_{P}^{4}$ , and $m \sim m_{E W} \sim T e V$ , the number of e-folds is $N \sim 25$ . Because the scale of inflation is low, this is sufficient to solve the horizon problem if the reheating temperature is $T_{RH} \ga MeV$. In this instance, the leading order coupling of $ϕ$ to matter via a dimension-8 operator $\frac{1}{m ^{4}} \partial_{μ} ϕ \partial_{ν} ϕ T^{μν}$ would lead to fermion-antifermion annihilation channels $f f ˉ \to ϕϕ$ accessible to the LHC, while yielding very weak corrections to the Newtonian potential and to supernova cooling rates, that are completely within experimental limits.

19 pages, latex, 3 .eps figures, v2: references added, to appear in PLB

Disformal Inflation

Abstract

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