The hubble tension as a hint of leptogenesis and neutrino mass generation

Abstract

The majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $$H_0$$ H 0 tension, however only if one introduces additional dark radiation at the level of $$\Delta N_{\mathrm{eff}} \sim 0.5$$ Δ N eff ∼ 0.5 . We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $$H_0$$ H 0 observed by the SH$$_0$$ 0 ES collaboration is expected to occur at the level of $$\sim 10\%$$ ∼ 10 % in the primordial majoron cosmology (to be compared with $$\sim 0.1\%$$ ∼ 0.1 % in the case of $$\Lambda $$ Λ CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $$H_0$$ H 0 .

Analyzing the Hubble tension through hidden sector dynamics in the early universe

“…and (2) the sectors were not in thermal equilibrium but eventually become thermalized [60][61][62] where a hidden sector particle decays to neutrinos after it becomes non-relativistic [5,7,63]. In the model discussed here, the particles in the dark sector are produced exclusively by SM processes.…”

“…One of the simplest avenues is the possibility of having extra relativistic degrees of freedom present during recombination, which would cause an increase in H 0 and bring it closer to its measured local value. Extensions of the SM with new particles in thermal equilibrium with the neutrinos, such as a majoron [4,5], or with an extra U (1) symmetry and Z bosons decaying to neutrinos or otherwise [6,7] can explain the tension. We note here that models that can successfully explain the Hubble tension are those where the extra degrees of freedom would affect only the dynamics in the CMB era, but not impact BBN.…”

Gravitational waves from first-order phase transitions in Majoron models of neutrino mass

“…[73] and it has been recently considered in refs. [74,75] in the context of the Hubble tension. We have introduced a flavor dependence since in our case the seesaw scale and the phase transition scale are different.…”

Hot New Early Dark Energy: Towards a Unified Dark Sector of Neutrinos, Dark Energy and Dark Matter

“…It has been known for a while now, that one of the most promising avenues for resolving the Hubble tension in cosmology is an extra component of DE, which decays just before recombination. In the first proposal of this type, called early dark energy (EDE) [10][11][12][13][14][15], the decay of this extra component of DE happened just before recombination in a second-order rollover of an axion-like scalar field (also see [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] for related work and [33][34][35][36][37][38][39][40][41] for other early-time approaches). But without fine-tuning of the axion potential the EDE component does not dilute fast enough after the transition to be in agreement with data.…”

“…As such it aims at providing a minimal and viable example of how the Hubble tension can guide our quest for a complete dark sector model. In our longer companion paper [52], we supplement our investigation with more technical details, a comparison between hot and 1 Although not as phenomenologically successful as NEDE, different attempts to relate the Hubble tension and the neutrino sector have been made in the past [33,39,49,50], most notably [20,24] explores the possibility that the EDE field is pushed up its potential when neutrinos become non-relativistic (see also [51] for a DE neutrino interaction). To our knowledge, our work is the first to use the NEDE phase transition for higgsing the neutrino sector.…”