HEP Theory Journal Club

Wave Interference in Self-Interacting Fuzzy Dark Matter

Christian Capanelli

McGill University

In the Fuzzy Dark Matter (FDM) scenario, the dark matter is composed of an ultra-light scalar field with a coherence length on the order of a kiloparsec. Naively, the early-time field configuration will exhibit order unity density fluctuations that are characteristic of wave-interference between free-streaming field modes. However, scalar fields generically have quartic self-interactions that can modify the field's dispersion. In this talk, I will describe the role that even feeble self-interactions have on the FDM free streaming and resulting density fluctuations. Namely, for a “warm” initial condition (motivated by post-inflationary ALP misalignment), I will characterize the effects of both attractive and repulsive self-interactions on the density power spectrum, studying the evolution over three relevant dynamical time scales. Finally, I will speculate on the application of our work to more realistic astrophysical environments.