Speaker
Description
Cosmic strings are one-dimensional topological defects predicted to form in the early universe after a phase transition by a variety of extensions of the Standard Model, ranging from axion models to grand-unified theories. After forming, strings are expected to decay via the emission of particles and gravitational waves (GWs), leading to the formation of a GW background (GWB) that may be detected by ongoing or future GW experiments. Traditionally, predictions of the GWB produced by cosmic strings are based on the Nambu-Goto approximation, in which the internal structure of the strings and their decay into particles are neglected. However, a correct interpretation of a positive GW signal would require of accurate predictions that go beyond the Nambu-Goto approximation and take into account the field-theory nature of the strings. As a first step to accurately characterize the GWB from a network of cosmic strings incorporating field-theory effects, we are focusing on understanding the evolution and decay-routes of closed strings, called loops, which in the NG approximation are expected to dominate the productions of GWs. Using field-theory lattice simulations, we have successfully characterized the emission of particles and GWs from loops, reaching a separation of scales of four orders of magnitude between the loop length and its core radius. In this talk, I will present the results from this study, showing evidence that, for the types of loops expected to appear in the early universe, the emission of particles always dominates over the production of GWs.
