3:30pm – Alex Gough
The complexity of dark matter multi-streaming encoded in wave interference
Dark matter dominates the evolution of the large scale structure of the universe, seeding the gravitational wells which galaxies then trace. Improving modelling techniques for the dynamics of dark matter is therefore essential to understanding the rich non-Gaussian structure of the cosmic web. On large scales, standard techniques treat cold dark matter as a perfect fluid, an approximation which breaks down as structure collapses and fluid streams cross, producing multi-stream regions. Modelling the dark matter field as a single, complex-valued wavefunction, one avoids the singular densities and difficulties of standard fluid techniques and instead replaces multi-streaming regions with interference patterns, decorating the density field in oscillations. We show how these interference patterns, akin to those from ultralight axions, can be “unwoven” into single-stream wavefunctions corresponding to classical fluid streams, as well as how the information beyond a perfect fluid can be isolated in the oscillations of the wavefunction. This description, together with links to diffraction integrals from optics, present rich universal features that can unlock new ways of modelling and probing both wavelike and cold dark matter on the scales of the cosmic web.