While the holy grail of #InhomogeneousCosmology is to explain #DarkEnergy as an epiphenomenon of the cosmologically recent formation epoch of #CosmicVoids and other #LargeScaleStructure, #YonadavBarryGinat and #PedroGFerreira have gone for a more modest goal: keeping the #CosmologicalConstant but tacking on void formation to get a sort-of #BeyondLCDM inhomogeneous model that better matches #DES and #DESI results [1].
#ArXiv_2601_20633
@cosmology #Cosmology #LCDM
[1] https://arxiv.org/abs/2601.20633
Apparent Dark-Energy Evolution from Cosmic Inhomogeneities
A mildly inhomogeneous universe with a cosmological constant may look like it contains evolving dark energy. We show that could be the case by modelling the inhomogeneities and their effects in three different ways: as clumped matter surrounded by voids, as back-reaction of small-scale structure on the overall expansion of the Universe, and, finally, as a large-scale curvature inhomogeneity. In all of these cases, the propagation of light is affected, and differs from that in a homogeneous and isotropic universe. The net result is that cosmological observables, such as angular diameter and luminosity distances, become distorted. We find, in all three models, that the inclusion of these effects pushes the distance-redshift relation towards closer agreement with recent data from both supernovae Ia from the Dark Energy Survey, and from baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument. The amount of inhomogeneity in these models might not be enough to explain the entirety of the deviation from a cosmological constant, but is found to be of a similar order of magnitude, hinting that these data may be consistent with a universe dominated by a cosmological constant.
For a first 'real' toot to @cosmology, here's the #InhomogeneousCosmology newsletter for September 2025, listing a bunch of recent papers [1]. The real Universe is not a uniform fluid – research on how to model the lumpy Universe properly according to general relativity is ongoing [1] – we generally call this #InhomogeneousCosmology .
[1] https://cosmo.torun.pl/mailman3/hyperkitty/list/[email protected]/thread/WTXMJOTM6OFYF2RMDZWO57LKZJCFHZFN
inhom newsletter September 2025 - Inhom - cosmo.torun.pl
#BigBang #InhomogeneousCosmology
#Cosmology
#Cosmic-Megastructure
"Intriguingly, the two structures are at the same distance from Earth, near the constellations of Boötes the Herdsman, raising the possibility that they are part of a connected cosmological system."
The size of these structures makes my head hurt.
https://www.theguardian.com/science/2024/jan/11/newly-discovered-cosmic-megastructure-challenges-theories-of-the-universe
Newly discovered cosmic megastructure challenges theories of the universe
A 1.3bn light year-sized ring discovered by PhD student in Lancashire appears to defy the cosmological principle assumption
#InhomogeneousCosmology newsletter December 2022 [1].
Asta Heinesen's "Reconciling a decelerating Universe with cosmological observations" ArXiv:2212.05568 [2] is very nice: it introduces a new theorem that focuses a key question of relativistic cosmology: is #DarkEnergy just a misinterpretation of the structure formation epoch?
Heinesen's theorem uses the past time cone directly.
[1] https://cosmo.torun.pl/pipermail/inhom/2022-December/000021.html
[2] https://arXiv.org/abs/2212.05568 = https://ui.adsabs.harvard.edu/abs/2022arXiv221205568H
#HeinesenTheorem
#Cosmology
[Inhom] inhom newsletter December 2022
Topological acceleration in the Universe (slides + audio)
The global topology of the spatial section of the Universe is currently unknown. It was first shown by Roukema et al (2007) that the existence of structure in the Universe implies effects of the global topology on local dynamics. Moreover, the effects of global topology on local dynamics, per the heuristic arguments used at the time, are topology dependent; different fundamental groups of homotopies give, in general, different dynamical effects. Thus, it appears that the global topology of the spatial section of our Universe, is, in principle, detectable by the the role of topological acceleration in the observed kinematics of the patterns of galaxies' peculiar velocities with respect to the comoving frame of a Friedmannian idealised reference model. The key argument for topological acceleration and later developments will be presented. Talk by B. Roukema @ASGRG2021, 3 Feb 2022 https://web.archive.org/web/20220208204431/https://www.asgrg2021.org/boudewijn-roukema webcam+audio: https://peertube.stream/w/8dvixyZTm85g2Q1e6jTw6f
NASA/ADS
A powerful, streamlined new Astrophysics Data System
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