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Abstract

We provide a comprehensive and up-to-date analysis of the prospects to
realize Dark Matter (DM) in the Inert Doublet Model, while simultaneously
enhancing the Electroweak Phase Transition (EWPhT) such as to allow for
electroweak baryogenesis. Instead of focusing on certain aspects or mass
hierarchies, we perform extensive, yet fine-grained, parameter space scans,
where we analyze the nature of the EWPhT in both the light and the heavy DM
regions, confronting it with the amount of DM potentially residing in the
lightest inert-doublet state. Thereby, we point out a viable region where a
non-trivial two-step EWPhT can appear, without being in conflict with
direct-detection bounds, which could leave interesting imprints in
gravitational wave signatures. We propose new benchmarks with this feature as
well as update benchmarks with a strong first-order transition in the light of
new XENON1T limits. Moreover, taking into account these latest bounds as well
as relevant collider constraints, we envisage a new region for light DM with a
small mass splitting, lifting the usual assumption of exact degeneracy of the
new non-DM scalars, such as to avoid collider bounds while providing a fair DM
abundance over a rather large DM mass range. This follows from a detailed
survey of the impact of co-annihilations on the abundance, dissecting the
various channels.