1 / 18

Exploring Cosmic Structures: Origami and Phase Space in Cosmology

This research delves into the fascinating concept of the universe as an origami structure, using phase space folds to analyze cosmic formations. With contributions from Johns Hopkins University researchers, the study focuses on Lagrangian coordinates for simulation analysis and identifies stream crossings and caustics as a means of morphology classification. The methodology incorporates stretching and contraction of the origami sheet to assist in halo finding, ultimately revealing how particles and structures evolve in both Eulerian and Lagrangian coordinates within the cosmos.

mitch
Download Presentation

Exploring Cosmic Structures: Origami and Phase Space in Cosmology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ORIGAMI: Structure finding with phase-space folds Mark Neyrinck Johns Hopkins University Eric Gjerde, origamitessellations.com

  2. Some collaborators: Bridget Falck, Miguel Aragón-Calvo, Guilhem Lavaux, Alex Szalay Johns Hopkins University

  3. Outline - The Universe as Origami - Lagrangian coordinates: perhaps underappreciated for simulation analysis - Finding stream-crossings/caustics: a parameter-free morphology classifier - Stretching/contraction of the “origami sheet” in position space also useful for halo finding • Mark Neyrinck, JHU

  4. (e.g. Bertschinger 1985) Spherical collapse in phase space • Mark Neyrinck, JHU

  5. A simulation in phase space: a 2D simulation slice vx x y z x y • Mark Neyrinck, JHU

  6. ORIGAMI Order-ReversIng Gravity, Apprehended Mangling Indices - 1d: particle in a halo if its order wrt any another particle is swapped compared to the original Lagrangian ordering - 3d: particle in a halo if this condition holds along 3 orthogonal axes (2 axes=filament, 1 axis=wall, 0 axes=void) - Need some diagonal axes as well - Finds places where streams have crossed • Mark Neyrinck, JHU

  7. 200 Mpc/h simulation, 0.8 Mpc/h cells δinitial

  8. log(1+δfinal) (measured using Voronoi tessellation) plotted on Lagrangian grid

  9. 200 Mpc/h simulation: # axes along which particle has crossed another particle (on Lagrangian grid) blue: 0 (void) cyan: 1 (sheet) yellow: 2 (filament) red: 3 (halo)

  10. Morphology of particles, showing Eulerian position.

  11. A 200 Mpc/h simulation: final-conditions morphology of particles, showing Eulerian position.

  12. Lines between initial, final positions, colored according to morphology.

  13. walls+filaments+haloes Fraction of dark matter in various structures. walls+filaments walls a

  14. How to group halo particles once they’re identified? - Eulerian: group adjacent particles in Voronoi tessellation (Lagrangian grouping better?) - Halo mass function (Knebe et al, Halo-finder comparison): • Mark Neyrinck, JHU

  15. How much does the origami sheet stretch? - Look at spatial part, ∇L⋅ψ. Lagrangian displacement ψ = xf - xi. ∇L⋅ψ ~ -δL. - ∇L⋅ψ = -3: halo formation, where ∇L⋅xf=0. • Mark Neyrinck, JHU

  16. Duality between structures in Eulerian, Lagrangian coordinates - Blobs become “points” (haloes) - Discs between blobs become filaments - Haloes look like voids in Lagrangian space! - Duality in Kofman et al. 1991, adhesion approx. • Mark Neyrinck, JHU

  17. Filaments often stretched out. - Could allow access to smaller-scale initial fluctuations than naively you would think?

  18. Origami - An interesting method to detect structures, independent of density Eric Gjerde, origamitessellations.com • Mark Neyrinck, JHU

More Related