Events at Physics |
Events on Thursday, June 18th, 2009
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Cosmic acceleration as the gravitational feedback of mass-varying dark matter
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Andre Fuzfa, GAMASCO, University of Namur (FUNDP); Louvain U; Paris Observatory;
- Abstract: 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 DM and DE are assumed physically unrelated. However, such DM-DE couplings make the mass of the DM particles varying, therefore breaking the universality of free fall (Galileo's equivalence principle). Doing so, the strong equivalence principle, stating the universality of gravitational binding energy, does not hold anymore, particularly where DM is profuse like in the large-scale universe. Mass-varying DM therefore induces modifications of gravity. This gravitational feedback on ordinary matter can explain cosmic acceleration, which is then interpreted as the observable signature of the violation of the equivalence principle on cosmological scales. To embrace the various physics of DM-induced violation of the equivalence principle, we have developped a generalisation of Brans-Dicke tensor-scalar theories of gravitation, dubbed the Abnormally Weighting Energy (AWE) Hypothesis. 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 late-time cosmic acceleration. Besides of describing both DM and DE, the AWE hypothesis allows measuring the density paramters of baryons and dark matter from the Hubble diagram *alone*, and its predictions are consistent with the independent cosmological tests of Cosmic Microwave Background (CMB) and Big Bang Nucleosynthesis (BBN). This interpretation also shed new light on the coincidence problem. We will end this seminar by showing how this mechanism could interestingly be applied to the physics of neutrino mass generation and mass-varying neutrinos by turning the spontaneous symmetry breaking of lepton number symmetry into a gravitational symmetry breaking.
- Host: S Mantry