  In this work we consider the two-dimensional Dirac operator with general
local singular interactions supported on a closed curve. A systematic study of
the interaction is performed by decomposing it into a linear combination of
four elementary interactions: electrostatic, Lorentz scalar, magnetic, and a
fourth one which can be absorbed by using unitary transformations. We address
the self-adjointness and the spectral description of the underlying Dirac
operator, and moreover we describe its approximation by Dirac operators with
regular potentials.
