  We investigate the strongly first-order electroweak phase transition using an
effective field theoretical approach. The standard effective field theory with
finite number truncation of higher dimensional operators fails in the typical
parameter space where the strongly first-order phase transition is realized
because it cannot describe the non-decoupling quantum effect of new physics
beyond the standard model. To parameterize the non-decoupling quantum effect,
we employ the nearly aligned Higgs effective theory in which the Higgs
potential is parameterized by a Coleman-Weinberg like form. Extending this
framework with finite temperature corrections, we study the parameter space for
realizing the strongly first-order phase transition, and estimate the
gravitational wave produced at the phase transition.
