Abstract
We extend a previous self-tuning analysis of the most general scalar-tensor theory of gravity in four dimensions with second order field equations by considering a generalized coupling to the matter sector. Through allowing a disformal coupling to matter we are able to extend the Fab Four model and construct a new class of theories that are able to tune away the cosmological constant on Friedmann-Lemaitre-Robertson-Walker backgrounds.
Highlights
Equation such that it counteracts the contribution from the particle content
We extend a previous self-tuning analysis of the most general scalar-tensor theory of gravity in four dimensions with second order field equations by considering a generalized coupling to the matter sector
Such a solution was realised through the derivation of a class of self-tuning theories, the so-called Fab-Four [26, 27], the argument here being that instead of concerning oneself over how to treat the vacuum energy contributions and radiative instability of the cosmological constant headon, one can instead mitigate the effects of the cosmological constant on the geometry seen by matter, i.e. it does not gravitate
Summary
We shall require that the geometry in both frames (Horndeski and Jordon, respectively) is FLRW To this end, in the Horndeski frame, we treat gμν, φ and ψi as the dynamical variables, with the Jordan-frame metric gμν being determined via (2.2). We assume that the Horndeski-frame metric gμν abides by the cosmological principle, i.e. we require that at any given instant in time t the geometry defined by gμν is spatially homogeneous and isotropic. This requirement is achieved by foliating spacetime into a set of spacelike. After some work we obtain the following expression for the Horndeski Lagrangian (3.1)
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