CP3 Lunch - Dark Energy and Dark Matter from Gravitational Symmetry Breaking - André Füzfa

Wednesday 14 Jan 2009, 13:00 → 13:50 Europe/Brussels

Cycl. 06

Coupling dark matter (DM) to dark energy (DE) is one of the most promising way to build a unified description of the invisible sector of cosmology. It also glimpses beyond the concordance model LCDM in which they are assumed physically unrelated. However, such DM-DE couplings make the mass of the DM particles varying, therefore breaking the equivalence principle. We have developped a generalisation of tensor-scalar theories of gravitation, dubbed the Abnormally Weighting Energy (AWE) Hypothesis, that embraces all the physics of such a violation of the equivalence principle by DM. In this approach, the variation of the inertial mass of DM particles induces a running of the gravitational coupling strength on cosmological scales that is observable in the cosmic acceleration. Besides of describing both DM and DE, the AWE hypothesis also shed new light on the coincidence problem. After briefly reminding the basics of the AWE hypothesis, we will mostly focus on a natural candidate for its realisation in particle physics in terms of the explicit symmetry breaking of a U(1) symmetry. In this model, the phase of a complex scalar becomes a pseudo-Nambu-Goldstone boson after explicit symmetry breaking of U(1) and can therefore account for (axion-like) DM particles. But the novelty of this mechanism is that the vacuum expectation value of the complex scalar, which eventually stands for DE, is not stabilized through some self-interaction potential but through the gravitational dynamics associated to its non-minimal couplings. We will show how the Hubble diagram of far-away type Ia supernovae allows to measure the scales of explicit and gravitational symmetry breakings. The cosmological parameters obtained from this analysis are also in agreement with cosmic concordance. We will conclude with some enticing consequences of this interpretation, notably possible links with neutrino physics. References: ------------ J.-M. Alimi, A. Füzfa, JCAP 09, 014 (2008) A. Füzfa, J.-M. Alimi, Phys. Rev. D 75, 123007 (2007) A. Füzfa, J.-M. Alimi, Phys. Rev. Lett. 97, 061301 (2006)