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.
Notre galaxie est attirée par une mystérieuse "structure géante" située à 300 millions d’années-lumière de nous
Découvrez Laniakea, un archipel galactique invisible à l’œil nu mais détectable grâce aux mouvements des galaxies dans l’espace.
Is the Universe a Fractal?
For decades cosmologists have wondered if the large-scale structure of the universe is a fractal: if it looks the same no matter the scale. And the answer is: no, not really. But in some ways, yes. Look, it’s complicated. Our universe is unimaginably vast and contains somewhere around two trillion galaxies. These galaxies aren’t scattered … Continue reading "Is the Universe a Fractal?"
Investigating Ultra-Large Large-Scale Structures: Potential Implications for Cosmology
Large-scale structure (LSS) studies in cosmology map and analyse matter in the Universe on the largest scales. Understanding the LSS can provide observational support for the Cosmological Principle (CP) and the Standard Cosmological Model ($Λ$CDM). In recent years, many discoveries have been made of LSSs that are so large that they become difficult to understand within $Λ$CDM. Reasons for this are: they potentially challenge the CP, (i.e. the scale of homogeneity); and their formation and origin are not fully understood. In this article we review two recent LSS discoveries: the Giant Arc (GA, $\sim 1$ Gpc) and the Big Ring (BR, $\sim 400$ Mpc). Both structures are in the same cosmological neighbourhood -- at the same redshift $z \sim 0.8$ and with a separation on the sky of only $\sim 12^\circ$. Both structures exceed the often-cited scale of homogeneity (Yadav+ 2010), so individually and together, these two intriguing structures raise more questions for the validity of the CP and potentially hint at new physics beyond the Standard Model. The GA and BR were discovered using a novel method of mapping faint matter at intermediate redshifts, interpreted from the MgII absorption doublets seen in the spectra of background quasars.
A simultaneous solution to the Hubble tension and observed bulk flow within 250 h−1 Mpc
Abstract. The ΛCDM standard cosmological model is in severe tension with several cosmological observations. Foremost is the Hubble tension, which exceeds 5σ con
Flat Patterns in Cosmic Structure
It is natural to wonder how far the flat pattern in the distribution of
galaxies and clusters of galaxies around the de Vaucoueurs Local Supercluster
extends, and whether there are other similarly extended flat patterns in cosmic
structure. I present evidence of two extended flat sheet-like patterns in the
distributions of galaxies and clusters detected at redshifts less than 0.021.
Sheet A contains our position and is tilted 11 degrees from the supergalactic
pole, meaning the Local Supercluster is a moderately bent part of the more
extended Sheet A. The continuation of this sheet is detected in the disjoint
sample of galaxies at redshifts 0.021 to 0.041 and of galaxies and clusters of
galaxies at redshifts 0.042 to 0.085. Sheet B is 15 Mpc from us at its closest
point. It is detected at redshift less than 0.021 and at redshift 0.021 to
0.041. These results make a serious case for the reality of signatures of close
to flat extended sheet-like patterns.
Alexia Lopez - A Giant Arc in the Sky
Boud
AlcorNews
Universe Today
Daniel Pomarède
JRDMB