Exotic see-saw mechanism for neutrinos and leptogenesis in a Pati-Salam model

Abstract

We discuss non-perturbative corrections to the neutrino sector, in the context of a D-brane Pati-Salam-like model, that can be obtained as a simple alternative to SO(10) GUT's in theories with open and unoriented strings. In such D-brane models, exotic stringy instantons can correct the right-handed neutrino mass matrix in a calculable way, thus affecting mass hierarchies and modifying the see-saw mechanism to what we name exotic see-saw. For a wide range of parameters, a compact spectrum of right-handed neutrino masses can occur that gives rise to a predictive scenario for low energy observables. This model also provides a viable mechanism for Baryon Asymmetry in the Universe (BAU) through leptogenesis. Finally, a Majorana mass for the neutron is naturally predicted in the model, leading to potentially testable neutron-antineutron oscillations. Combined measurements in neutrino and neutron-antineutron sectors could provide precious informations on physics at the quantum gravity scale.

Limiting first-order phase transitions in dark gauge sectors from gravitational waves experiments

“…On the other hand, our model can be UV completed in context intersecting D-brane parallel worlds. In this case, extra non-perturbative terms like H 6 1 , H 6 2 , ... softly breaking the Z 2 symmetry can be generated by exotic E-brane instantons, similarly to mechanisms suggested in our recent papers in various contexts [37][38][39][40] 5 . As well, inflaton couplings with the Oand D-sectors are the same at perturbative level, while exotic instantons can generate soft Z 2 -breaking corrections leading to an asymmetric reheating of the O-and D-sectors (T = T ).…”

The fate of Schwarzschild–de Sitter black holes in f(R) gravity

“…For a review on stringy instantons see [47]. Stringy instantons have also other intriguing implications in particle physics as discussed in [48][49][50][51][52][53][54][55][56][59][60][61]. Finally, if a classical Nariai black hole is reinterpreted as an ensemble of horizonless naked singularities, as recently suggested in [63][64][65], one could relax conditions considered in the Bousso-Hawking-Nojiri-Odintsov analysis.…”

Neutron-antineutron transitions from exotic instantons: How fast they might be and further implications

“…In particular, we have suggested several explicit models generating a Majorana mass for the neutron. [1][2][3][4][5][6][7][8][9] Such a signature can be tested in the next generation of experiments in neutron-antineutron physics improving the present limit of τ 3 yrs (in vacuum), up to τ 300 yrs.…”