Small-scale structure in vector dark matter

Abstract

We investigate the differences in the small-scale structure of vector dark matter (VDM) and scalar dark matter (SDM) using 3+1 dimensional simulations of single/mul­ticomponent Schrödinger-Poisson system. We find that the amount of wave interference, core-to-halo mass ratio (and its scatter), spin of the core, as well as the shape of the central regions of dark matter halos can distinguish VDM and SDM. Starting with a collection of idealized halos (self-gravitating solitons) as an initial condition, we show that the system dynamically evolves to an approximately spherically symmetric configuration that has a core surrounded by a halo of interference patterns in the mass density. In the vector case, the central soliton in less dense and has a smoother transition to an r -3 tail compared to the scalar case. As compared to SDM, wave interference in VDM is ∼ 1/√3 times smaller, resulting in fewer low and high density regions, and more diffuse granules in the halo. The ratio of VDM core mass to the total halo mass is lower than that in SDM, with a steeper dependence on the total energy of the system and a slightly larger scatter. Finally, we also initiate a study of the evolution of intrinsic spin angular momentum in the VDM case. We see a positive correlation between the total intrinsic spin in the simulation and the spin of the final central core, with significant scatter. We see large intrinsic spin in the core being possible even with vanishing amounts total angular momentum in the initial conditions (at least instantaneously). Our results point towards the possibility of distinguishing VDM from SDM using astrophysical and terrestrial observations.

i-SPin: An integrator for multicomponent Schrödinger-Poisson systems with self-interactions

“…For instance, they are present in the low-energy effective theory of vector dark matter arising from an Abelian Higgs model (with a heavy Higgs field). These interactions can lead to interesting modifications to the phenomenology of vector dark matter formation [43][44][45][46][47][48][49], blackhole superradiance [50][51][52][53], and impact nonlinear small-scale structure in such dark matter [11][12][13]54]. As discussed in [14,55], they also remove the energy degeneracy between polarized vector solitons which could potentially impact their cosmological population.…”

“…Physical systems described by Schrödinger(-like) equations are ubiquitous in many areas of physics, ranging from (ultra-)light dark matter in cosmology [1][2][3][4][5][6][7][8][9][10][11][12][13][14], to terrestrial systems in non-linear optics [15][16][17][18][19][20][21][22], water waves [23][24][25] and Bose-Einstein condensates (BEC) [26][27][28][29][30][31][32]. Apart from long-range interactions such as gravity in the astrophysical/cosmological context, or external potential in laboratory settings, the Schrödinger field can have point-like quartic selfinteractions, with its evolution determined by time-dependent Gross-Pitaevskii(-like) equations.…”

Dark photon dark matter from an oscillating dilaton

“…Halos supported by dark photons can therefore feature vector solitonic cores [5] reminiscent of those in scalar fuzzy DM models [1]. However, these vector solitons are distinguished due to their intrinsic spins [7,8]. The vectorlike nature of the condensate also allows for distinctive higher energy solitonic configurations similar to Proca stars with radially directed vector fields [5].…”

“…Vector dark matter's predictions for small-scale structure also differ considerably from its scalar cousin due to the nature of its production mechanisms, which typically result in a highly peaked power spectrum on small scales [11][12][13][14][15]. Such a peaked spectrum leads to rich small-scale structure, with significant energy density stored in boson stars [8,16].…”

“…Recent studies on dynamical heating of ultrafaint dwarf galaxies via coherent fluctuations in fuzzy dark matter put pressure on the very low mass end of the mass spectrum, requiring m fdm > 10 −19 eV [17]. Slightly weaker limits are expected to apply to the vector scenario due to the reduced interference of the multiple polarization states [8]. Reference [18] argues that a generic bound m fdm > 10 −18 eV applies when dark matter is produced by a causal process after inflation.…”