The Friedrichs extension of the Aharonov-Bohm Hamiltonian on a disk

We show that the Aharonov–Bohm Hamiltonian considered on a disc has a four-parameter family of self-adjoint extensions. Among the in- finitely many self-adjoint extensions, we determine to which parameters the Friedrichs extension H F corresponds and its lowest eigenvalue is found. Moreover, we note that the diamagnetic inequality holds for H F .