arXiv subjects

Camille Bonvin

Publications and source records attributed to Camille Bonvin.

76 records · Page 5Linked to original sources

arXiv2007

Generalized Einstein-Aether theories and the Solar System

It has been shown that generalized Einstein-Aether theories may lead to significant modifications to the non-relativistic limit of the Einstein equations. In this paper we study the effect of a general class of such theories on the Solar System. We consider corrections to the gravitational potential in negative and positive powers of distance from the source. Using measurements of the perihelion shift of Mercury and time delay of radar signals to Cassini, we place constraints on these corrections. We find that a subclass of generalized Einstein-Aether theories are compatible with these constraints.

astro-ph↗

arXiv2007

Superluminal motion and closed signal curves

We discuss some properties of Lorentz invariant theories which allow for superluminal motion. We show that, if signals are always sent forward in time, closed curves along which signals propagate can be formed. This leads to problems with causality and with the second law of thermodynamics. Only if one singles out one frame with respect to which all signals travel forward in time, the formation of 'closed signal curves' can be prevented. However, the price to pay is that in some reference frames perturbations propagate towards the past or towards the future, depending on the direction of emission.

astro-ph↗

arXiv2006

No-go theorem for k-essence dark energy

We demonstrate that if k-essence can solve the coincidence problem and play the role of dark energy in the universe, the fluctuations of the field have to propagate superluminally at some stage. We argue that this implies that successful k-essence models violate causality. It is not possible to define a time ordered succession of events in a Lorentz invariant way. Therefore, k-essence cannot arise as low energy effective field theory of a causal, consistent high energy theory.

astro-ph↗

arXiv2006

Dipole of the luminosity distance: a direct measure of H(z)

We show that the dipole of the luminosity distance is a useful observational tool which allows us to determine the Hubble parameter as a function of the redshift H(z). We determine the number of supernovae needed to achieve a given precision for H(z) and to distinguish between different models for dark energy. We analyse a sample of nearby supernovae and find a dipole consistent with the cosmic microwave background at a significance of more than 2 sigma.

astro-ph↗