Fermionic currents in topologically nontrivial braneworlds

TL;DR

This paper studies how a brane affects the vacuum current density of charged fermions in a locally AdS spacetime with compact dimensions, revealing that the brane-induced current is localized near the brane and analyzing specific applications including graphene tubes.

Contribution

It provides a detailed analysis of fermionic current densities in braneworlds with compact dimensions, including the effects of boundary conditions and applications to graphene.

Findings

Brane-induced current is mainly near the brane and vanishes at boundaries.

Current density remains finite on the brane.

Applications to Randall-Sundrum models and graphene tubes demonstrate the theory's relevance.

Abstract

We investigate the influence of a brane on the vacuum expectation value (VEV) of the current density for a charged fermionic field in background of locally AdS spacetime with an arbitrary number of toroidally compact dimensions and in the presence of a constant gauge field. Along compact dimensions the field operator obeys quasiperiodicity conditions with arbitrary phases and on the brane it is constrained by the bag boundary condition. The VEVs for the charge density and the components of the current density along uncompact dimensions vanish. The components along compact dimensions are decomposed into the brane-free and brane-induced contributions. The behavior of the latter in various asymptotic regions of the parameters is investigated. It particular, it is shown that the brane-induced contribution is mainly located near the brane and vanishes on the AdS boundary and on the horizon. An important feature is the finiteness of the current density on the brane. Applications are given to $Z_2$-symmetric braneworlds of the Randall-Sundrum type with compact dimensions for two classes of boundary conditions on the fermionic field. In the special case of three-dimensional spacetime, the corresponding results are applied for the investigation of the edge effects on the ground state current density induced in curved graphene tubes by an enclosed magnetic flux.