Continuum Dark Matter

TL;DR

This paper introduces a novel dark matter model based on a gapped continuum of states, providing a new framework for understanding its cosmological evolution and detection prospects.

Contribution

It develops an effective field theory for gapped continuum dark matter and explores its cosmological and phenomenological implications, including a concrete WIC model.

Findings

Reproduces observed relic density of dark matter

Avoids direct detection constraints via continuum kinematics

Predicts continuous and cascade decays of dark matter

Abstract

We initiate the study of dark matter models based on a gapped continuum. Dark matter consists of a mixture of states with a continuous mass distribution, which evolves as the universe expands. We present an effective field theory describing the gapped continuum, outline the structure of the Hilbert space and show how to deal with the thermodynamics of such a system. This formalism enables us to study the cosmological evolution and phenomenology of gapped continuum DM in detail. As a concrete example, we consider a weakly-interacting continuum (WIC) model, a gapped continuum counterpart of the familiar WIMP. The DM interacts with the SM via a Z-portal. The model successfully reproduces the observed relic density, while direct detection constraints are avoided due to the effect of continuum kinematics. The model has striking observational consequences, including continuous decays of DM states throughout cosmological history, as well as cascade decays of DM states produced at colliders. We also describe how the WIC theory can arise from a local, unitary scalar QFT propagating on a five-dimensional warped background with a soft wall.