Quasi-spherical collapse of matter in ΛCDM. Issue 4 (7th February 2019)

• Record Type: Journal Article
• Authors: Rampf, Cornelius
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 484:Issue 4(2019)
• Page Start: 5223
• Page End: 5235
• Publication Date: 2019-02-07
• Subjects: cosmology: theory -- dark matter -- large-scale structure of Universe; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz372
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We report the findings of new exact analytical solutions to the cosmological fluid equations, namely for the case where the initial conditions are perturbatively close to a spherical top-hat profile. To do so we enable a fluid description in a Lagrangian-coordinates approach, and prove the convergence of the Taylor-series representation of the Lagrangian displacement field until the time of collapse ('shell-crossing'). This allows the determination of the time for quasi-spherical collapse, which is shown to happen generically earlier than in the spherical case. For pedagogical reasons, calculations are first given for a spatially flat universe that is only filled with a non-relativistic component of cold dark matter (CDM). Then, the methodology is updated to a ΛCDM Universe, with the inclusion of a cosmological constant Λ > 0.