Talk detail

Participant	Arai, Shun
Institution	Nagoya University - Furocho - Nagoya - Aichi - Japan

Session	EU2C	Accepted		Order	Time
Talk	Oral abstract	Title	Inflationary perturbations with Lifshitz scaling
Coauthors
Abstract	We consider primordial perturbations with a single inflaton field in the framework of 4d-Horava-Lifshitz gravity. For the sake of Lorentz violation in the Horava Lifshitz gravity, all the components obey the dispersion relations with Lifshitz scaling and one additional scalar degree of freedom appears, this is called “Khonon”. Since the Khronon gravitationally couples to the inflaton, the generation of an isocurvature perturbation could be expectable. However, we show that the curvature perturbation is preserved at super-horizon scales and the isocurvature is irrelevant to the primordial spectra at linear approximation. This is due to the mass acquisition of the Khronon before the horizon exit. Consequently, we reveal that the primordial fluctuations at Lifshitz regime are consistent with cosmological observations. Moreover, we found that the detection of primordial gravitational waves can test Lorentz symmetry of the gravity sector at the inflationary energy scale, where it is the highest energy scale for the experimental test of Lorentz symmetry in gravity. This talk is based on the paper arXiv: 1803.01352.
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Session	DE1	Accepted		Order	Time
Talk	Oral abstract	Title	Generalized criterion of thawing and freezing models in Horndeski theory
Coauthors
Abstract	The thawing and freezing criterion is well known as the division of the dark energy models with a quintessence field, depending on the signature of the time derivative of the equation of state of dark energy (EoSofDE). Not only the criterion well traces the shapes of a potential of the field, but also it is able to be investigated by cosmological observations. We generalize the thawing and freezing criterion for the model-classification in Horndeski theory. We consider the cases when matters minimally couple with gravity and the EoSofDE is defined in terms of the Freedman equations previously provided in Bellini and Sawicki 2014. In this set-up, we numerically confirm that the criterion we made significantly partitions the EFT parameters given in Bellini and Sawicki 2014. In particular, the models whose gravitational couplings deviate from the Newton constant, we find there is a tight correlation between the sign of the time derivative of EoSofDE and that of the Planck mass run rate at low redshifts below z=1. In the end, we discuss the consequences of our criterion for the observational constraints on the Horndeski theory.
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