Models of non-relativistic quantum gravity: the good, the bad and the healthy

By D. Blas, O. Pujolàs, S. Sibiryakov. 2010

334 citations recorded by the source corpus.

Hořava’s proposal for non-relativistic quantum gravity introduces a preferred time foliation of space-time which violates the local Lorentz invariance. The foliation is encoded in a dynamical scalar field which we call ‘khronon’. The dynamics of the khronon field is sensitive to the symmetries and other details of the particular implementations of the proposal. In this paper we examine several consistency issues present in three non-relativistic gravity theories: Hořava’s projectable theory, the healthy non-projectable extension, and a new extension related to ghost condensation. We find that the only model which is free from instabilities and strong coupling is the non-projectable one. We elaborate on the phenomenology of the latter model including a discussion of the couplings of the khronon to matter. In particular, we obtain the parameters of the post-Newtonian expansion in this model and show that they are compatible with current observations.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/9753b6e25e6b78652db284702a8d0be6f93ae9b0

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Citations in the corpus

Hořava-Lifshitz gravity from dynamical Newton-Cartan geometry (2015, methodology): “More precisely the Khronon field φ of [31] corresponds to what we call τ and what is called uμ in [31] corresponds to what we call τμ.”
Exploring gravitational theories beyond Horndeski (2014, methodology): “Such an approach has already been used in the past to study, for instance, the behavior of specific models of Horava’s gravity [29].”
Maximal freedom at minimum cost: linear large-scale structure in general modifications of gravity (2014, positive): “This is to allow for direct implementation of our formulation in codes as CAMB [13] or CLASS [14, 15].”
Tests of Lorentz invariance: a 2013 update (2013, background): “The emission from radio to low-energy γ -rays (E 1 GeV) is thought to be synchrotron radiation from relativistic electrons, whereas IC scattering by these electrons is the favoured explanation for the higher energy γ -rays.”
Dark Energy in Light of Multi-Messenger Gravitational-Wave Astronomy (2018, background): “The special case of Einstein-Aether theories in which the vector field is the gradient of a scalar is known as Khronometric [54].”
The effective field theory of dark energy (2012, background): “The invariant object under this symmetry is the unit vector perpendicular to the constant time hypersurfaces n—defined in (5)—and to lowest order in derivatives the action can be written as [71, 74]”
Imperfect Dark Energy from Kinetic Gravity Braiding (2010, result): “In fact, in this sense the situation in the present model quite similar to ghost condensation [3] and Hořava gravity [71, 72, 73]”
Bouncing Cosmologies: Progress and Problems (2016, background): “One of them is called the “projectable version”, another is the original version [89] extended by terms which were only implicit in the original version - the “healthy extension” [94].”
Degenerate higher order scalar-tensor theories beyond Horndeski and disformal transformations (2016, background): “Indeed, the Lagrangians that remain invariant under a field redefinition of the scalar field correspond to khronometric theories [20], which are a subset of Einstein-Aether theories [21].”
Modified Gravity and Cosmology (2011, background): “HL gravity in its various guises has been reviewed in a number of articles [1016, 1166, 1266, 926, 170].”