Speaker
Description
A series of symmetry-breaking phase transitions in the early universe is expected to have caused the formation of networks of sheet-like topological defects called domain walls, whose collapse could leave observable imprints in current-day massive non-linear structures. We use the parameter-free version of the velocity-dependent one-scale model to provide an estimate of their decay energy, which is expected to act as a seed for density perturbations of the background matter field. We calculate the current mass of the resulting non-linear objects depending on collapse redshift and wall tension, and thus show that domain walls can be responsible for the formation of objects with masses up to those of current-day galaxy clusters. Based on this, we estimate the maximal fraction of such objects and confirm that the contribution of standard domain walls to structure formation is always subdominant. Networks of walls based on a biased scalar field potential, however, are subject to much less stringent observational constraints, allowing for a significantly larger collapse energy. Based on our analysis, we are able to show that the collapse of such biased wall networks can provide a significant contribution to structure formation, and, in particular, a mass excess at high redshifts of z ≥ 9 as suggested by JWST data.
