Self-Interaction Bounds on Ultralight Dark Matter Couplings to Matter

TL;DR

This paper shows that self-interaction bounds on ultralight dark matter (ULDM) can strongly constrain its couplings to matter, especially neutrinos, electrons, and quarks, using astrophysical and cosmological observations.

Contribution

It demonstrates that quantum loop-induced self-interactions impose significant limits on ULDM couplings, impacting experimental and observational searches.

Findings

Self-interaction bounds exclude large ULDM-neutrino coupling parameter space.

Constraints on ULDM-electron and quark couplings can surpass equivalence principle tests.

Cosmic microwave background and structure formation data provide robust limits on ULDM interactions.

Abstract

Ultralight dark matter (ULDM) couplings to matter fields and ULDM self-interactions are typically treated as independent probes. However, since the ULDM-matter couplings unavoidably induce self-interactions through quantum loop corrections, bounds on self-interacting ULDM from astrophysical and cosmological observations will also limit the coupling strength to matter. Applying this argument, we find that self-interaction bounds can impose strong constraints on the linear ULDM couplings to neutrinos, excluding a large portion of parameter space that is widely considered for probing ULDM via neutrino oscillation experiments. In addition, the self-interaction bounds also limit the quadratic ULDM couplings to electrons and light quarks, which can become stronger than from the stringent test of equivalence-principle violation. Our results demonstrate that the extreme observational sensitivity of cosmic microwave background and structure formations to repulsive self-interactions can robustly translate into powerful constraints on the ULDM interactions with fundamental particles.