Garchinger Maier-Leibnitz-Kolloquium: Reheating the Universe and Role of Effective Gravitational Interactions

by Dr Simon Clery (Physik Department, TUM)

Thursday 22 May 2025, 16:15 → 17:15 Europe/Berlin

Lecture hall, ground floor (west) (LMU building, Am Coulombwall 1, campus Garching)

Cosmic inflation is currently the most promising theory for depicting the initial conditions in the early Universe. In the simplest models, a scalar field, the inflaton, is slowly rolling down its potential with high energy density, making the Universe to expand exponentially. Inflationary predictions for large-scale cosmological perturbations originating from inflaton quantum fluctuations match perfectly with the observation of the Cosmic Microwave Background (CMB) temperature anisotropy.  However, for an inflationary model to be successful, it also needs to include a viable mechanism to transfer energy to produce the particles of the Standard Model (SM) and possibly a dark matter sector. In the standard reheating scenario, the inflaton field falls towards the potential minimum, ending the accelerated expansion and oscillates around this minimum. It can then dissipate its energy while oscillating, and convert it into particles through its coupling to other fields. In this presentation, I explore the phenomenology of reheating through perturbative effects. I especially study the production of particles during inflaton oscillations, mediated by Planck-suppressed effective gravitational interactions. I consider the graviton portals and generalize these results to non-minimal couplings to gravity. This framework is applied to the  production of heavy dark matter (DM) particles, as well as the production of relativistic particles of the SM. I show that the right relic abundance of DM could be produced through these gravitational portals and that such unavoidable gravitational effects may highly impact the early radiation production from the inflaton. We finally propose a minimal scenario in which both the DM relic abundance and the asymmetry between baryons and anti-baryons, are generated by the gravitational portals during reheating, relying on the process of non-thermal leptogenesis. This involves a Beyond Standard Model (BSM) scenario with additional heavy right-handed neutrinos.

Hybrid access via ZOOM:
https://lmu-munich.zoom.us/j/98457332925?pwd=TWc3V1JkSHpyOTBPQVlMelhuNnZ1dz09
Meeting ID: 984 5733 2925
Passcode: 979953

 

 

kolloquium-22-05-25.pdf