Bubble wall velocity: heavy physics effects

A strongly-coupled sector can feature a supercooled confinement transition in the early universe. We point out that, when fundamental quanta of the strong sector are swept into expanding bubbles of the confined phase, the distance between them is large compared to the confinement scale. We suggest a modelling of the subsequent dynamics and find that the flux linking the fundamental quanta deforms and stretches towards the wall, producing an enhanced number of composite states upon string fragmentation. The composite states are highly boosted in the plasma frame, which leads to additional particle production through the subsequent deep inelastic scattering. We study the consequences for the abundance and energetics of particles in the universe and for bubble-wall Lorentz factors. This opens several new avenues of investigation, which we begin to explore here, showing that the composite dark matter relic density is affected by many orders of magnitude.

Section: Jhep04(2021)278mentioning

confidence: 86%

“…On the other hand, the run-away wall dashed line, and hence the string fragmentation line, could be affected by this choice. For simplicity as well as in light of the criticism of[92] appeared in[93,126], we employed the results of[72] in this paper.…”

mentioning

confidence: 99%

String fragmentation in supercooled confinement and implications for dark matter

Baldes

Gouttenoire

Sala

2021

“…For the bubble wall speed we simply take v w = 1 in the gravitational wave amplitude, noting that there remains considerable debate in the literature as to the leading effects which contribute to this quantity; see for example refs. [121,[124][125][126][127][128]. In the following, for simplicity, we will continue to use the same names for the approximations as in section 5, though one should bear in mind these additional limitations with regard to bubble nucleation and the bubble wall speed.…”

Section: The Consequences For Gravitational Wave Predictionsmentioning

confidence: 99%

On the perturbative expansion at high temperature and implications for cosmological phase transitions

Gould

Tenkanen

2021

We revisit the perturbative expansion at high temperature and investigate its convergence by inspecting the renormalisation scale dependence of the effective potential. Although at zero temperature the renormalisation group improved effective potential is scale independent at one-loop, we show how this breaks down at high temperature, due to the misalignment of loop and coupling expansions. Following this, we show how one can recover renormalisation scale independence at high temperature, and that it requires computations at two-loop order. We demonstrate how this resolves some of the huge theoretical uncertainties in the gravitational wave signal of first-order phase transitions, though uncertainties remain stemming from the computation of the bubble nucleation rate.

“…Bubble walls are assumed to expand at a constant speed v w [68], which is determined by how the wall interacts with the surrounding plasma in the interplay between bubble expansion and frictional forces [69,70]. Fluid friction is thought to prevent runaway acceleration in phase transitions in gauge theories, although the details of the interactions between the particles of the plasma and the wall are under debate [71][72][73]. Ref.…”

Section: First Order Phase Transitionsmentioning

confidence: 99%

Gravitational waves from a holographic phase transition

Ares

Hindmarsh

Hoyos

et al. 2021

We investigate first order phase transitions in a holographic setting of five-dimensional Einstein gravity coupled to a scalar field, constructing phase diagrams of the dual field theory at finite temperature. We scan over the two-dimensional parameter space of a simple bottom-up model and map out important quantities for the phase transition: the region where first order phase transitions take place; the latent heat, the transition strength parameter α, and the stiffness. We find that α is generically in the range 0.1 to 0.3, and is strongly correlated with the stiffness (the square of the sound speed in a barotropic fluid). Using the LISA Cosmology Working Group gravitational wave power spectrum model corrected for kinetic energy suppression at large α and non-conformal stiffness, we outline the observational prospects at the future space-based detectors LISA and TianQin. A TeV-scale hidden sector with a phase transition described by the model could be observable at both detectors.