Speaker
Description
Grand unified theories and other extensions of the Standard Model predict topological defects such as Cosmic strings. These are 1-dimensional strings, formed during the symmetry-breaking phase transitions of the early universe. Propagating strings created overdense envelopes of primordial gas (called wakes), resulting in overdensities of neutral hydrogen. The electrons in ground-state neutral hydrogen undergo a hyperfine transition, either emitting or absorbing 21 cm radiation, which has redshifted to radio band frequencies. Cosmic string wakes will exhibit enhanced or reduced emissions of 21 cm, which would be distinguishable on data captured by radio interferometers. We conduct the first observational search for these signatures in radio interferometric data. We present simulations of cosmic string wake signals incorporating foreground contamination, cosmological noise, and the realistic instrumental response of the Murchison Widefield Array (MWA), leveraging years of archival data alongside recent observations. The wake signatures have a characteristic ridge-like pattern in Fourier space. To exploit geometric pattern detection and filter Gaussian noise, we test higher-order correlation functions (3-point or higher), and compare them with a Gaussian Process regression approach, which models the correlation of noise and data points. Together, the simulation framework and analysis pipeline motivate our MWA data analysis strategy, aiming to detect or place upper limits on the string tension Gµ.