HEP Theory Journal Club

Accretion onto Oscillating Cosmic String Loops

Jiao Hao

McGill

Cosmic string loops could act as non-linear seeds in the early universe and play an important role in explaining many phenomena which are in tension with the standard ΛCDM model. Hence, the accretion process onto cosmic string loops should be studied in detail. Most previous works view loops as point masses and ignore the impact of the finite loop size. We utilize the Zel’dovich approximation to calculate the non-linear mass sourced by a static extended loop with a time-averaged density profile derived from the trajectory of the loop oscillation, and compare the result with what is obtained with a point-mass source. We find that the finite size of a loop mainly affects the evolution of turnaround shells during the early stages of accretion, converging to the point mass result after a critical redshift. The total accreted mass surrounding a loop is suppressed relative to the point mass case. As an immediate extension, we also qualitatively analyze the accretion onto moving point masses and onto moving extended loops. In addition to the reduction in the nonlinear mass, the loop finite size also changes the shape of the turnaround surface at the early stages of accretion.