Topology and geometry of the dark matter web: a multistream view

TL;DR

This paper investigates the cosmic web's topology and geometry using multistream fields, revealing that voids dominate the single-streaming regions and that Hessian eigenvalues can identify dark matter structures.

Contribution

It introduces a multistream perspective to cosmic web analysis, highlighting topological differences from traditional density-based methods and proposing eigenvalue-based geometric indicators.

Findings

Void regions occupy over 99% of single-streaming areas.

Percolating structures in multistream fields are thinner than in over-density approaches.

Hessian eigenvalues effectively delineate filaments, walls, and haloes.

Abstract

Topological connections in the single-streaming voids and multistreaming filaments and walls reveal a cosmic web structure different from traditional mass density fields. A single void structure not only percolates the multistream field in all the directions, but also occupies over 99 per cent of all the single-streaming regions. Sub-grid analyses on scales smaller than simulation resolution reveal tiny pockets of voids that are isolated by membranes of the structure. For the multistreaming excursion sets, the percolating structure is significantly thinner than the filaments in over-density excursion approach. Hessian eigenvalues of the multistream field are used as local geometrical indicators of dark matter structures. Single-streaming regions have most of the zero eigenvalues. Parameter-free conditions on the eigenvalues in the multistream region may be used to delineate primitive geometries with concavities corresponding to filaments, walls and haloes.