Theory HEP Seminar

The Hubble Tension: A Particle Physics Perspective

Miguel Escudero

TUM

We are living exciting times in Cosmology and we may be at the edge of a shift in the cosmological paradigm. At present, there is a 4-5 sigma tension in the value of the Hubble constant between the value that is inferred locally (from Cepheids and type Ia Supernovae) and the value predicted in LCDM. This tension has been growing for the past 6-7 years and many models have been proposed to account for it.

In the first part of this seminar, I will review the status of the Hubble tension. I will discuss the observational situation and review the main theoretical approaches developed to account for it. In the second part of the talk, I will focus on my contribution to the topic (see arxiv:1909.04044, arxiv:2004.01470, arxiv:2103.03249). I will show that the Hubble tension can be substantially ameliorated in the presence of an eV-scale pseudo-Goldstone boson that interacts with neutrinos: the Majoron. This particle is directly related to the neutrino mass mechanism and naturally arises in the context of the type-I seesaw mechanism with a spontaneously broken global U(1)L symmetry. Remarkably, I will further show that in some regions of the parameter space, this scenario could also account for the observed baryon asymmetry of the Universe via sterile neutrino oscillations in the early Universe. Thus, providing an intriguing link between low-scale leptogenesis, neutrino mass generation and the Hubble tension.