SEARCH FOR COSMIC STRINGS IN THE COSMOS SURVEY — STUDIES PERTAINING GALAXY-GALAXY CORRELATION AND CROSS-CORRELATION

Abstract

The COSMOS survey is investigated for the presence of cosmic strings, indicated by observations of galaxy pairs that are consistent with the gravitational lensing signature of a cosmic string. Employing a new technique combining the simulation of cosmic strings at the catalog level and relying on the correlation and cross-correlation of galaxy pairs to deduce their morphological similarity, no evidence indicating the existence of straight and static cosmic strings is observed at tile position 55 of the COSMOS survey for a string with energy-density/relative-tilt of 5” and redshift of 1. Cosmic strings are hypothetical one-dimensional topological defects thought to have been formed in the early universe during the first fraction of a second after the Big Bang, as a result of phase transitions in different regions of spacetime. The existence of cosmic strings will undoubtedly provide solid evidence towards the understanding of the early universe, especially during the Planck epoch and earlier. Present theories about the early universe propose an intensely hot, dense and violent environment, whereby such a dense primordial soup of matter (the first matter to exist in the universe) underwent a series of phase transitions at high temperatures in different regions of spacetime present after the expansion from the singularity. 1 These phase transitions involve the breaking and restoration of symmetry, as described by quantum field theory. 2 The effects of high temperature should be accounted for, as a result of the early universe being very hot and dense immediately after the Big Bang. In this section, we shall consider the Abelian Higgs model 2 and assume that the cosmic strings formed are non-superconducting and local (i.e. the Lagrangian describing the energy density of the string is invariant under a symmetry transformation which may be different at every point), 1 and in addition take into account that the phase transitions are occurring in a radiationdominated FRW universe. 1 The early universe may be thought of as being in the symmetric phase when it was very hot and dense, with no strings being formed initially. However, when the