Ruiz Ruiz, FernandoGibbons, G.W.Ortiz, M.E.2023-06-202023-06-201990-04-190370-269310.1016/0370-2693(90)90407-Whttps://hdl.handle.net/20.500.14352/59055Copyright © 1990 Published by Elsevier B.V.It is shown that any sigma model coupled to gravity with a target space having closed geodesics admits singular cosmic string solutions with event horizons. We also prove that if one makes the general assumption of boost symmetric sources, non-singular solutions of this type cannot exist. The case of the target manifold being the fundamental domain of the modular group PSL(2,¢Z) is discussed in detail.journal articlehttp://dx.doi.org/10.1016/0370-2693(90)90407-Whttp://www.sciencedirect.commetadata only access53PhysicsMultidisciplinaryFísica (Física)22 Física