Fermionic current densities induced by magnetic flux in a conical space with a circular boundary

TL;DR

This paper studies how magnetic flux in a conical spacetime with a circular boundary influences fermionic vacuum currents, revealing periodic flux dependence and boundary effects on charge density and azimuthal current.

Contribution

It provides new analytical results for fermionic vacuum expectation values in conical geometries with boundaries, including boundary-induced effects and asymptotic behaviors.

Findings

Vacuum charge density and azimuthal current are periodic in magnetic flux.

Boundary conditions induce nonzero charge density for massless fields.

Vacuum expectation values decay exponentially at large distances from the boundary.

Abstract

We investigate the vacuum expectation value of the fermionic current induced by a magnetic flux in a (2+1)-dimensional conical spacetime in the presence of a circular boundary. On the boundary the fermionic field obeys MIT bag boundary condition. For irregular modes, a special case of boundary conditions at the cone apex is considered, when the MIT bag boundary condition is imposed at a finite radius, which is then taken to zero. We observe that the vacuum expectation values for both charge density and azimuthal current are periodic functions of the magnetic flux with the period equal to the flux quantum whereas the expectation value of the radial component vanishes. For both exterior and interior regions, the expectation values of the current are decomposed into boundary-free and boundary-induced parts. For a massless field the boundary-free part in the vacuum expectation value of the charge density vanishes, whereas the presence of the boundary induces nonzero charge density. Two integral representations are given for the boundary-free part in the case of a massive fermionic field for arbitrary values of the opening angle of the cone and magnetic flux. The behavior of the induced fermionic current is investigated in various asymptotic regions of the parameters. At distances from the boundary larger than the Compton wavelength of the fermion particle, the vacuum expectation values decay exponentially with the decay rate depending on the opening angle of the cone. We make a comparison with the results already known from the literature for some particular cases.