Oscillations and Random Walk of the Soliton Core in a Fuzzy Dark Matter Halo

TL;DR

This paper explains the oscillations and random walk behavior of soliton cores in fuzzy dark matter halos as wave interference phenomena, using eigenmode analysis to connect core dynamics with halo evolution and tidal disruption effects.

Contribution

It introduces an eigenmode analysis framework to understand soliton core oscillations and random walks as wave interference, linking core behavior to halo evolution and tidal effects.

Findings

Oscillations and random walks are due to wave interference of eigenstates.

Eigenmode analysis explains core dynamics during tidal disruption.

Reduced excited states lead to diminished core oscillations.

Abstract

A Fuzzy Dark Matter (FDM) halo consists of a soliton core close to the center and an NFW-like density profile in the outer region. Previous investigations found that the soliton core exhibits temporal oscillations and random walk excursions around the halo center. Analyzing a set of numerical simulations, we show that both phenomena can be understood as the results of wave interference -- a suitable superposition of the ground (solitonic) state and excited states in a fixed potential suffices to account for the main features of these phenomena. Such an eigenmode analysis can shed light on the evolution of a satellite halo undergoing tidal disruption. As the outer halo is stripped away, reducing the amplitudes of the excited states, the ground state evolves adiabatically. This suggests diminished soliton oscillations and random walk excursions, an effect to consider in deducing constraints from stellar heating.