Topological Defects in Cosmology

Abstract

The place of cosmic strings and other topological defects in modern cosmology is reviewed, particularly focussing on their potential role in large-scale structure formation. Most emphasis is given to cosmic strings but the cosmological implications of global monopoles and global textures are also summarized. String structure and properties are briefly introduced, before discussing the formation and evolution of a string network in an expanding universe. The gravitational effects of the conical string spacetime are delineated along with potential observational consequences such as gravitational lensing, Doppler effects in the microwave background, and black hole formation. The formalism for calculating gravitational radiation by loops and long strings is presented, leading to a discussion of experimental constraints on the stochastic background predicted by strings. We then consider the present status of the cosmic string scenario for large-scale structure formation presenting normalizations for galactic and CMBR scales. Finally, the properties and evolution of global monopoles and textures are introduced, before discussing their respective gravitational effects and large-scale structure scenarios.