Dynamics of Wave Structures in Multifield Fuzzy Dark Matter Halos

Abstract

As a natural extension of the single-field fuzzy dark matter (FDM) model, multifield FDM has attracted increasing attention in recent years. This scenario is motivated both by the axiverse scenario predicted by string theory and by the possibility that multifield FDM may provide a better match to astrophysical observations than its single-field counterpart. In this work, we perform high-resolution numerical simulations to systematically investigate the dynamics of wave structures in multifield FDM halos. In particular, we study the oscillatory and stochastic motions of the central core, the evolution and statistical properties of granules, and the resulting dynamical heating of embedded stellar systems. We find that the frequency spectra of the core density oscillations develop multiple peaks and shift toward higher frequencies relative to the single-field case. The centers of different field components undergo nearly synchronized random walks, while subdominant components exhibit larger random-walk amplitudes. We further show that the suppression of granule density fluctuations with increasing number of fields is largely insensitive to the fractional abundance of each component over a broad parameter range. Moreover, using self-consistent simulations, we find that the dynamical heating induced by granules is progressively suppressed as the number of fields increases. However, once the contribution from the central core is taken into account, this trend would become much less pronounced.

12 pages, 11 figures