Cosmological Origami: Properties of Cosmic-Web Components when a Non-Stretchy Dark-Matter Sheet Folds

TL;DR

This paper introduces an origami-inspired model of cosmic structure formation where a non-stretchy dark matter sheet folds to create the cosmic web, providing insights into the formation of nodes, filaments, and walls.

Contribution

It presents a novel origami approximation for cosmological structures, modeling the dark matter sheet as a non-stretchy surface that folds to form cosmic web components.

Findings

Nodes form via polygonal collapse in 2D.

In 3D, nodes form through polyhedral collapse.

The model relates masses, arrangements, and angular momenta of structures.

Abstract

In the current cosmological paradigm, an initially flat three-dimensional manifold that pervades space (the `dark-matter sheet') folds up to build concentrations of mass (galaxies), and a cosmic web between them. Galaxies are nodes, connected by a network of filaments and walls. The folding is in six-dimensional (3D position, plus 3D velocity) phase space. The positions of creases, or caustics, mark the edges of structures. Here, I introduce an origami approximation to cosmological structure formation, in which the dark-matter sheet is not allowed to stretch. But it still produces an idealized cosmic web, with nodes, filaments, walls and voids. In 2D, nodes form in `polygonal collapse' (a twist-fold in origami), necessarily generating filaments simultaneously. In 3D, nodes form in `polyhedral collapse,' simultaneously generating filaments and walls. The masses, spatial arrangement, and angular momenta of nodes and filaments are related in the model. I describe some `tetrahedral collapse', or tetrahedral twist-fold, models.