Reconciling ALP Dark Matter and Electroweak Baryogenesis through First-Order Electroweak Phase Transition

TL;DR

This paper proposes a model where an axionlike particle (ALP) explains dark matter and baryon asymmetry by leveraging a first-order electroweak phase transition, which also produces a detectable gravitational wave signal.

Contribution

It introduces a novel mechanism where ALP dynamics during a first-order EWPT generate both dark matter and baryon asymmetry, linking cosmological phenomena with phase transition physics.

Findings

ALP potential reshaped during EWPT induces large ALP velocities.

The model broadens the parameter space for ALP dark matter.

Predicts a stochastic gravitational-wave signal from the EWPT.

Abstract

We show that an axionlike particle (ALP) can simultaneously generate the baryon asymmetry and constitute dark matter through dynamics triggered by a first-order electroweak phase transition (EWPT). In our proposal, the transition briefly reshapes the ALP potential via a temperature-dependent vacuum expectation value of a scalar field $S$, responsible for making the EWPT of first order, inducing a transient mass enhancement of ALP via higher-dimensional $U(1)$-breaking operator(s). This sudden kick generates a large ALP velocity near the onset of EWPT enabling the broadening of relic satisfied parameter space and predict a complementary stochastic gravitational-wave signal from the underlying first-order transition. We further show that the same ALP dynamics can naturally fuel electroweak baryogenesis through its coupling to electroweak anomaly.