Séminaire / Seminar GReCO |
| « Field theoretical formulations of MOND-like gravity » |
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J.-P. Bruneton |
| More than twenty years ago, Milgrom made the hypothesis that the unusual dynamics of galaxies may not originates from the presence of an unknown type of (dark) matter but rather from a modification of the non relativistic limit of General Relativity. This proposal, dubbed MOND (Modification of Ordinary Newtonian Dynamics), is amazingly successful at reproducing many aspects of galactic dynamics. However, a consistent relativistic theory of gravitation reproducing this phenomenology is still lacking. We examine critically the various attempts made in the literature to derive such a modified Newtonian dynamics from relativistic field theories, and notably the TeVeS theory of Bekenstein (2004). We notably insist on hyperbolicity of field equations, causality, instabilities and fine-tuning, and derive some new experimental constraints. Finally we present a new attempt at reproducing MOND dynamics from a simple Brans-Dicke theory in vacuum, whereas non Newtonian dynamics arises from a non-minimal coupling to the matter sector. This theory may be seen as a particular realization of an extended class of scalar-tensor theories. Although the idea is appealing, asking the MOND phenomenology at low acceleration scales seems to spoil the consistency of the scalar field equation within matter, and fine-tuning may be required. |
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lundi 5 février 2007 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |