Theoretical uncertainties for cosmological first-order phase transitions
  We critically examine the magnitude of theoretical uncertainties in
perturbative calculations of first-order phase transitions, using the Standard
Model effective field theory as our guide. In the usual daisy-resummed
approach, we find large uncertainties due to renormalisation scale dependence,
which amount to two to three orders-of-magnitude uncertainty in the peak
gravitational wave amplitude, relevant to experiments such as LISA.
Alternatively, utilising dimensional reduction in a more sophisticated
perturbative approach drastically reduces this scale dependence, pushing it to
higher orders. Further, this approach resolves other thorny problems with daisy
resummation: it is gauge invariant which is explicitly demonstrated for the
Standard Model, and avoids an uncontrolled derivative expansion in the bubble
nucleation rate.
