# Beyond General Relativity, Beyond Cosmological Standard Model

1-5 July 2019
Faculty of Physics, University of Warsaw
Europe/Warsaw timezone

## Could the H0 Tension be Pointing Toward the Neutrino Mass Mechanism?

1 Jul 2019, 18:10
20m
Faculty of Physics, University of Warsaw

#### Faculty of Physics, University of Warsaw

conference hall 0.03, Faculty of Physics, University of Warsaw ul. Pasteura 5, 02-093 Warszawa Poland
contributed talk

### Speaker

Miguel Escudero (King's College London)

### Description

Within the framework of $\Lambda$CDM, the local determination of the Hubble constant disagrees -- at the 4.4$\sigma$ level -- with that inferred from the very accurate CMB observations by the Planck satellite. This clearly motivates the study of extensions of the standard cosmological model that could reduce such tension. Proposed extensions of $\Lambda$CDM that reduce this so-called Hubble tension require an additional component of the energy density in the Universe to contribute to radiation at a time close to recombination.

In this talk, I will show that pseudo-Goldstone bosons -- associated with the spontaneous breaking of global lepton number in type-I seesaw models -- lead to a non-standard early Universe evolution that can help to reduce the Hubble tension. I will show that current CMB observations can set a lower bound on the scale at which lepton number is broken as high as 1 TeV. Finally, I will argue that future CMB observations will test wide and relevant regions of parameter space of scenarios in which the spontaneous breaking of global lepton number is the mechanism behind the observed neutrino masses.

### Primary author

Miguel Escudero (King's College London)

### Co-author

Samuel Witte (IFIC (CSIC-Universidad de Valencia))