Technically natural dark energy from Lorentz breaking

Monday June 6, 14:30hs -  Seminar room

Speaker: Serguey Sibiryakov (INR, Moscow)

Abstract:

I will present a model of dark energy with a technically natural small contribution to cosmic acceleration, i.e. this contribution does not receive corrections from other scales in the theory.

The proposed acceleration mechanism appears generically in the low-energy limit of gravity theories with violation of Lorentz invariance that contain a derivatively coupled scalar field -- Theta. The latter may be the Goldstone field of a broken global symmetry. The model, that we call Theta-CDM, is a valid effective field theory up to a high cutoff just a few orders of magnitude below the Planck scale. Furthermore, it can be ultraviolet-completed in the context of Horava gravity. I will discuss the observational predictions of the model. Even in the absence of a cosmological constant term, the expansion history of the Universe is essentially indistinguishable from that of Lambda-CDM. The difference between the two theories appears at the level of cosmological perturbations. In Theta-CDM the matter power spectrum is enhanced at subhorizon scales compared to Lambda-CDM. This property can be used to discriminate the model from Lambda-CDM with current cosmological data.

 

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