Talk detail

Participant	Hees, Aurelien
Institution	Royal Observatory of Belgium - Avenue Circulaire, 3 - Bruxelles - Bruxelles - Belgium

Session	AT2	Accepted	Yes	Order	9	Time		20'
Talk	Oral abstract	Title	Combined cosmological and solar system constraints on Chameleon mechanism
Co-authors	A. Füzfa
Abstract	The chameleon mechanism appearing in massive tensor-scalar theory of gravity can effectively reduce the effect of the nonminimal coupling between the scalar field and matter. This mechanism is invoked to reconcile cosmic acceleration produced by a departure from General Relativity on large-scales and the stringent constraints on General Relativity on small-scales. In this communication, we will briefly review the Chameleon mechanism before considering its efficiency to explain cosmic acceleration on one hand and solar system constraints on the other. It is found that the non-minimal coupling considerably extends the range of parameters allowing to explain cosmic acceleration compared with quintessence. We then discuss how solar system constraints on PPN parameters further reduce the parameter space of chameleon theories, leaving no overlap in parameter space for the usual Ratra-Peebles inverse law potential.

Session	SG1	Accepted	Yes	Order	4	Time	15:05
Talk	Oral abstract	Title	Simulations of solar system observations in alternative theories of gravity
Co-authors	B. Lamine, S. Reynaud, M.T. Jaekel, C. Le Poncin-Lafitte, V. Lainey, A. Füzfa, J.M. Courty, V. Dehant, P. Wolf
Abstract	There is still a great interest to test General Relativity. Within the solar system, the gravitational observations are always related to radio science measurements (Range and Doppler) or to angular measurements of light (position of body in the sky, VLBI). In order to have an idea of the signature and of the order of magnitude that an hypothetical theory of gravitation can have on solar system observations, we developed a new software that simulates range/Doppler/angular signals. We will present this new tool that simulates radio science observations directly from the space-time metric . We will present range/Doppler simulations of Cassini spacecraft in an alternative theory of gravity going beyond standard Post-Newtonian formalism and we will show how it is possible to derive constraint on this alternative gravitation theory.