Strongly First-Order Electroweak Phase Transition and Classical Scale
  Invariance
  In this work, we examine the possibility of realizing a strongly first-order
electroweak phase transition within the minimal classically scale invariant
extension of the standard model (SM), previously proposed and analyzed as a
potential solution to the hierarchy problem. By introducing one complex singlet
scalar and three right-handed Majorana neutrinos, the scenario was successfully
capable of achieving a radiative breaking of the electroweak symmetry
(Coleman-Weinberg Mechanism), inducing non-zero masses for the SM neutrinos
(seesaw mechanism), presenting a pseudoscalar dark matter candidate, and
predicting the existence of a second $CP$-even boson in addition to the 125 GeV
scalar. We construct the full finite-temperature one-loop effective potential
of the model, including the resummed thermal daisy loops, and demonstrate that
finite-temperature effects induce a first-order electroweak phase transition.
Requiring the thermally-driven first-order phase transition to be sufficiently
strong further constrains the model's parameter space; in particular, an
$\mathcal O(0.01)$ fraction of the dark matter in the universe may be
simultaneously accommodated with a strongly first-order electroweak phase
transition. Moreover, such a phase transition disfavors right-handed Majorana
neutrino masses above several hundreds of GeV, confines the pseudoscalar dark
matter masses to $\sim 1$-2 TeV, predicts the mass of the second $CP$-even
scalar to be $\sim 100$-300 GeV, and requires the mixing angle between the
$CP$-even components of the SM doublet and the complex singlet to lie within
the range $0.2 \lesssim \sin\omega \lesssim 0.4$. The obtained results are
displayed in comprehensive exclusion plots, identifying the viable regions of
the parameter space. Many of these predictions lie within the reach of the next
LHC run.
