Consequences of a gravitational θ-term in the neutrino sector

It is known that non-perturbative effects in QCD break chiral symmetry and give rise to the η' meson. As widely believed, also gravity violates global symmetries, since microscopic black holes or wormholes may take away global charges from our universe. Based on a topological 3-form formulation of gravity, it was recently shown that the consequent gravitational θ-term inevitably leads to a new pseudoscalar degree of freedom in the neutrino sector, analogous to the η'. The appearance of such a ''Goldstone'' boson due to anomaly is a general feature of the topological 3-form language and not necessarily related to the confining characteristics of QCD. In the current research project, we investigate the rich theoretical and experimental consequences of this new topological degree of freedom in the neutrino sector.