COSMIC STRINGS WITH POSITIVE Λ

We discuss cosmic Nielsen-Olesen strings in space-times endowed with a positive cosmological constant. For the cylindrically symmetric, static free cosmic string, we discuss the contribution of the cosmological constant to the angle deficit, and to the motion of the null/timelike geodesics. For a non-gravitating cosmic string in a Schwarzschild-de Sitter space-time, we discuss how a thin string can pierce the two horizons. We also present a metric which describes the exterior of a self gravitating thin string present in the Schwarzschild-de Sitter space-time.