Seminarium "Teoria cząstek elementarnych i kosmologia"

We present an updated analysis of the first-order phase transition associated with symmetry breaking in the early Universe in a classically scale-invariant model extended with a new SU(2) gauge group. Including recent developments in understanding supercooled phase transitions, we compute all of its characteristics and constrain the parameter space. We then predict gravitational-wave spectra generated during this phase transition. Next, by computing the signal-to-noise ratio, we conclude that this model is well testable(and falsifiable) with LISA. We also provide predictions for the relic dark matter abundance. It is consistent with observations in a rather narrow part of the parameter space, as we exclude the so-called supercool dark matter scenario based on an improved description of percolation and reheating after the phase transition. Finally, we pay special attention to renormalisation-scale dependence of the results. Even though our main results are obtained with the use of renormalisation-group improved effective potential, we also present the outcome of a fixed-scale analysis. It proves that the dependence on the scale is not only qualitative but also quantitative.