Paper
Fuzzy dark matter halos with repulsive self-interactions: coherent soliton and halo vortex network with moderate self-coupling
Authors
Milos Indjin, Nick Keepfer, I-Kang Liu, Nick P. Proukakis, Gerasimos Rigopoulos
Abstract
We examine the impact of moderate repulsive self-interactions on fuzzy dark matter halos generated by merging smaller Gaussian density concentrations. We study the size of the core and the granules, the spatial dependence of the field's coherence, the turbulent vortex tangle and the oscillation frequency of the central soliton, covering the range from quantum-pressure-dominated to self-interaction-dominated stabilisation of the solitonic core. For the probed self-coupling strengths and with a fixed initial configuration, mergers with increasing result in cores with increased size and a reduced central density, oscillating with decreased frequency, in accordance with expectations from the study of isolated Self-interacting Fuzzy Dark Matter (SFDM) solitons. By contrast, the characteristic granule size and typical inter-vortex distances in the surrounding halo are only mildly affected, growing much less relative to the core. The total length of the vortex network, although less robust, shows no signs of decay over our simulation timescales. The generated halos therefore develop central self-interaction-dominated cores, but with the outer halos still supported by quantum-pressure and classical kinetic energy in equipartition as in the non-interacting case. Furthermore, measures of coherence of the field clearly separate the condensed core, identified via the Penrose-Onsager (largest eigenvalue) mode of the entire classical field, from the surrounding quasi-coherent halo. Unlike the case, we observe a relative increase of incoherent fluctuations coexisting with the coherent mode at the centre of the halo with increasing , a phenomenon also observed in laboratory condensates at non-zero temperature.