Black Hole-Wormhole transition in (2+1) Einstein -- anti-de Sitter Gravity Coupled to Nonlinear Electrodynamics

In this paper we present two results in $(2+1)$ gravity coupled to nonlinear electrodynamics. First it is determined the general form of the electromagnetic field tensor in $(2+1)$ gravity coupled to nonlinear electrodynamics in stationary cyclic spacetimes. Secondly, it is determined a family of exact solutions in $(2+1)$ gravity sourced by a nonlinear electromagnetic field. The solutions are characterized by five parameters: mass $M$, angular momentum $J$, cosmological constant $\Lambda$ and two electromagnetic charges, $q_{\alpha}$ and $q_{\beta}$. Remarkably, the solution can be interpreted as a traversable wormhole, provided the fulfillment of certain inequalities by the characteristic parameters; fine tunning of the cosmological constant leads to an extreme black hole, whereas by switching off one of the electromagnetic charges, we obtain the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole.