Neutron–hidden-neutron mixing as an effective component of galactic dark matter

We investigate the possibility that neutron–hidden-neutron mixing provides an effective source of dark matter through the non-trivial vacuum condensate associated with fermion mixing in quantum field theory. In a static and spherically symmetric curved spacetime, the mixed-vacuum expectation value of the energy–momentum tensor can acquire the form of a pressureless fluid and therefore contribute to the gravitational field. In the weak-field limit, this condensate generates a Yukawa correction to the Newtonian potential. Following the analysis previously developed for neutrino mixing, we reproduce the observed baryonic Tully–Fisher scaling. Our results indicate that the vacuum condensate induced by neutron–hidden-neutron mixing can act as an effective dark-matter component on galactic scales.