Vortices in ultralight darkish matter halos may reveal new clues to cosmic construction

The nature of darkish matter stays one of many best mysteries in cosmology. Within the usual framework of non-collisional chilly darkish matter (CDM), varied fashions are thought-about: WIMPs (Weakly Interacting Massive Particles, with plenty of round 100 GeV/c²), primordial black holes, and ultralight axion-like particles (mass of 10^-22 to 1 eV/c²). In the latter case, darkish matter behaves like a wave, described by a Schrödinger equation, slightly than as a group of level particles. This generates particular behaviors at small scales, whereas following normal dynamics (CDM) at massive scales.

Philippe Brax and Patrick Valageas, researchers on the Institute of Theoretical Physics, studied fashions of ultralight chilly darkish matter with repulsive self-interactions, whose dynamics are described by a non-linear variant of the Schrödinger equation, referred to as the Gross-Pitaevskii equation, additionally encountered within the physics of superfluids and Bose-Einstein condensates. In their work, the authors observe the formation and dynamics of explicit constructions, known as “vortices” (whirlpools) and “solitons” (cores in hydrostatic equilibrium), inside halos of rotating ultralight darkish matter.

The papers are published in the journal Physical Review D.

As with a superfluid studied within the laboratory, in these fashions, darkish matter cores are described by the equations of an “irrotational” fluid. The system can then solely maintain general rotation via the looks of singularities, i.e., “vortices” (whirlpools).

Combining analytical and numerical approaches, the authors present that rotating darkish matter halos certainly give rise to such vortices, which additional manage right into a secure rotating community within the halo’s core. These vortices have a quantized angular momentum that is determined by the mass of the darkish matter particle. Due to centrifugal power, the “soliton” (darkish matter core) acquires an axisymmetric, flattened form.

If these vortices actually exist, they might provide a brand new approach to detect ultralight darkish matter. For instance, by analyzing the gravitational signatures they go away in galaxies. It would even be fascinating to check the attainable hyperlink between these “vortex lines” and the filaments of the cosmic net. Thus, vortices analogous to these noticed within the laboratory in quantum superfluid physics may exist in darkish matter halos on astrophysical or galactic scales.