Weekly Update from the Open Journal of Astrophysics – 18/10/2025

It’s time once again for the usual Saturday update of the week’s new papers at the Open Journal of Astrophysics. Since the last update we have published four  more papers, which brings the number in Volume 8 (2025) up to 156, and the total so far published by OJAp up to 391.

I’d like to encourage people to follow our feed on the Fediverse via Mastodon (where I announce papers as they are published, including the all-important DOI) so this week I’ll include links to each announcement there.

The first paper to report is “Shot noise in clustering power spectra” by Nicolas Tessore (University College London, UK) and Alex Hall (University of Edinburgh, UK). This was published in the folder Cosmology and NonGalactic Astrophysics on Tuesday October 14th 2025. This presents a discussion of the effects of ‘shot noise’, an additive contribution due to degenerate pairs of points, in angular galaxy clustering power spectra. Here is a screen grab of the overlay:

You can find the officially accepted version of the paper here. The Mastodon announcement is here:

Open Journal of Astrophysics

@[email protected]

New Publication at the Open Journal of Astrophysics: "Shot noise in clustering power spectra" by Nicolas Tessore (University College London, UK) and Alex Hall (University of Edinburgh, UK)

https://doi.org/10.33232/001c.145919

Next one up is “The Giant Arc – Filament or Figment?” by Till Sawala and Meri Teeriaho (University of Helsinki, Finland). This paper discusses the abundance of large arc-like structures formed in the standard cosmological model, with reference to the “Giant Arc” identified in MgII absorption systems. It was published on Wednesday October 15th in the folder Cosmology and NonGalactic Astrophysics. The overlay is here:

The officially accepted version of this paper can be found on the arXiv here and the Mastodon announcement is here:

Open Journal of Astrophysics

@[email protected]

New Publication at the Open Journal of Astrophysics: "The Giant Arc – Filament or Figment?" by Till Sawala and Meri Teeriaho (University of Helsinki, Finland)

https://doi.org/10.33232/001c.145931

The third paper this week,  published on Monday 6th October, is “Detecting wide binaries using machine learning algorithms” by Amoy Ashesh, Harsimran Kaur and Sandeep Aashish (Indian Institute of Technology, Patna, India). This was published on Friday 17th October (yesterday) in the folder Astrophysics of Galaxies. It presents a method for detecting wide binary systems in Gaia data using machine learning algorithms.

The overlay is here:

You can find the officially accepted version of this paper on arXiv here. The announcement on Mastodon is here:

Open Journal of Astrophysics

@[email protected]

New Publication at the Open Journal of Astrophysics: "Detecting wide binaries using machine learning algorithms" by Amoy Ashesh, Harsimran Kaur and Sandeep Aashish (Indian Institute of Technology, Patna, India)

https://doi.org/10.33232/001c.146027

The last one this week is “Learned harmonic mean estimation of the Bayesian evidence with normalizing flows” by Alicja Polanska & Matthew A. Price (University College London, UK), Davide Piras (Université de Genève, CH), Alessio Spurio Mancini (Royal Holloway, London, UK) and Jason D. McEwen (University College London). This one was also published on Friday 17th October, but in the folder Instrumentation and Methods for Astrophysics; it presents a new method for estimating Bayesian evidence for use in model comparison, illustrated with a cosmological example.

The corresponding overlay is here:

You can find the officially accepted version on arXiv here. The Mastodon announcement is here:

Open Journal of Astrophysics

@[email protected]

New Publication at the Open Journal of Astrophysics: "Learned harmonic mean estimation of the Bayesian evidence with normalizing flows" by Alicja Polanska & Matthew A. Price (University College London, UK), Davide Piras (Université de Genève, CH), Alessio Spurio Mancini (Royal Holloway, London, UK) and Jason D. McEwen (University College London)

https://doi.org/10.33232/001c.146026

That concludes the papers for this week. With two weeks to go I think we might reach the 400 total by the end of October.

#arXiv240505969v3 #arXiv250511072v2 #arXiv250619942v3 #arXiv250703749v2 #BayesInference #BayesianModelComparison #CosmologyAndNonGalacticAstrophysics #DiamondOpenAccess #DiamondOpenAccessPublishing #GAIA #GaiaDR3 #galaxyClustering #GiantArc #InstrumentationAndMethodsForAstrophysics #largeScaleStructureOfTheUniverse #Mastodon #MgIIAbsorptionSystems #normalizingFlows #OpenJournalOfAstrophysics #ShotNoise #WideBinaries

#Cosmology

Gigaparsec structures are nowhere to be seen in ΛCDM: an enhanced analysis of LSS in FLAMINGO-10K simulations

by Alexia Lopez @morninglopez and Roger Clowes @rgclowes
https://arxiv.org/abs/2504.14940

#GiantArc #BigRing #galaxies #astrodon #science #STEM #news

Big Things in the Universe

About a year ago I wrote a couple of articles (here and here) in response to the discovery of a very large structure (“The Big Ring“) and claims that this structure and others – such as a Giant Arc – were inconsistent with the standard model of cosmology; the work concerned was later submitted as a preprint to arXiv. In my first post on the Big Ring I wrote

To assess the significance of the Big Ring or other structures in a proper scientific fashion, one has to calculate how probable that structure is given a model. We have a standard model that can be used for this purpose, but to simulate very structures is not straightforward because it requires a lot of computing power even to simulate just the mass distribution. In this case one also has to understand how to embed Magnesium absorption too, something which may turn out to trace the mass in a very biased way. Moreover, one has to simulate the observational selection process too, so one is doing a fair comparison between observations and predictions.

Well on today’s arXiv there is a preprint by Sawala et al. with the title aims to assess the significance of structures comparable to the Giant Arc. The title of the paper is The Emperor’s New Arc: gigaparsec patterns abound in a ΛCDM universe from which you can guess the conclusions. The abstract is

Recent discoveries of apparent large-scale features in the structure of the universe, extending over many hundreds of megaparsecs, have been claimed to contradict the large-scale isotropy and homogeneity foundational to the standard (ΛCDM) cosmological model. We explicitly test and refute this conjecture using FLAMINGO-10K, a new and very large cosmological simulation of the growth of structure in a ΛCDM context. Applying the same methods used in the observations, we show that patterns like the “Giant Arc”, supposedly in tension with the standard model, are, in fact, common and expected in a ΛCDM universe. We also show that their reported significant overdensities are an algorithmic artefact and unlikely to reflect any underlying structure.

arXiv:2502.03515

Here’s a picture of a large structure (a “Giant Arc”) taken from a gallery of such objects found in the simulations

I quote from the conclusions:

We hope that our results will dispel the misconception that no inhomogeneity can be found in the standard model Universe beyond some finite size. Instead, any given realisation of the isotropic universe comprises a time- and scale-dependent population of structures from which patterns can be identified on any scale.

I have nothing to add.

#arXiv250203515 #BigRing #Cosmology #GiantArc #LambdaCDM

in the #arXiv

Investigating Ultra-Large Large-Scale Structures: Potential Implications for Cosmology

by Alexia Lopez @morninglopez and co-authors
https://arxiv.org/abs/2409.14894

#cosmology #bigring #giantarc #galaxies #ΛCDM #CosmologicalPrinciple #LSS #LargeScaleStructure #Universe #astrodon #astronomy #astrophysics #science #STEM #RoyalSociety

World’s top cosmologists convene to question conventional view of the universe

The principle that ⭐️everything looks the same everywhere⭐️ is a fundamental pillar of the standard model of #cosmology,
which aims to explain the big bang and how the universe has evolved in the 13.7bn years since.
But this week a meeting of some of the world’s leading cosmologists will convene at London’s Royal Society to ask:
what if this basic assumption is wrong?

The meeting comes after a number of high-profile astronomical observations have challenged the conventional view, according to Prof Subir #Sarkar, a cosmologist at the University of Oxford and co-organiser of the meeting.
“We are, in cosmology, using a model that was first formulated in 1922,” he said. “We have great data, but the theoretical basis is past its sell-by date. More and more people are saying the same thing and these are respected astronomers.”

The conference brings together some of the scientists behind the recent anomalous findings.
These include
🌟observations that suggest the universe is expanding more quickly in some regions than others,
🌟hints at megastructures in the night sky and evidence for cosmic flows
– vast celestial rivers of material on a scale that cannot be readily accommodated within conventional theories.
Dr Nathan #Secrest, of the US Naval Observatory and a collaborator with Sarkar, is presenting findings that raise
🌟the possibility that the universe is slightly lopsided. After analysing a catalogue of more than 1m quasars (extremely luminous galactic cores), the team found that one hemisphere of the sky appeared to host roughly 0.5% more sources than the other.
It may not sound like a major discrepancy but, according to Sarkar, if confirmed
🔸 it would undermine the basis for #dark #energy, 🔸which is supposed to be the dominant component of the universe.
“It would mean that two-thirds of the universe has just disappeared,” Sarkar said.

Dr Konstantinos #Migkas, of Leiden University, will share
🌟findings that the Hubble constant – the rate at which the universe is expanding
– appears to vary across space.
“Our results add another problematic piece to the puzzle,” Migkas said. At a local scale, at least, this suggests that observations do not match predictions of the standard model. “We can’t extrapolate that it’s wrong over the full universe,” he added.

Alexia #Lopez, a PhD student at the University of Central Lancashire, has discovered what appear to be
🌟cosmic megastructures, named #BigRing and #GiantArc. These shapes, traced out by galaxies and galaxy clusters, occur on a scale beyond which the universe should be smooth and effectively featureless.
“When we’re finding a list of structures that are exceeding this scale, are they challenging this assumption that is so fundamental in cosmology?” said Lopez. “Maybe there needs to be more of a critical analysis of our standard model.”

Sarkar suggests that belief in the standard model of cosmology has been so deeply ingrained that it is treated as “the religion”. “I find that frankly annoying that this principle hasn’t been checked,” he said,
although not everyone agrees with this characterisation.

Prof George #Efstathiou, an astrophysicist at the University of Cambridge, who is presenting a more sceptical take at the conference, ♦️said it was not true that the model had not been repeatedly interrogated. ♦️“People accuse me of defending the model,” he said. “But what they don’t realise is how much time I’ve spent trying to disprove it. I completely disagree that’s there’s some kind of groupthink.”

Efstathiou said that while intriguing, none of the anomalies being presented were compelling enough to undermine standard theories.
https://www.theguardian.com/science/2024/apr/14/worlds-top-cosmologists-convene-to-question-conventional-view-of-the-universe?CMP=Share_iOSApp_Other

Very interesting paper by @govertschilling for Sky and Telescope, on the discovery of the Big Ring by @morninglopez et al., with quotes from Jim Peebles (“I am hoping for anomalies that could prove to be empirical hints to a better theory”), Carlos Frenk, and Rien van de Weijgaert.

https://skyandtelescope.org/astronomy-news/astronomers-find-big-ring-1-3-billion-light-years-across/

#cosmology #bigring #giantarc #galaxies #quasars #standardmodel #ɅCDM #JimPeebles #NobelPrize #physics #BigBang #astronomy #astrophyscis #astrodon #science #space #news #research #STEM

"Two extraordinary uLSSs (ultra-large-scale structures) in such close configuration raises the possibility that together they form an even more extraordinary cosmological system."

➡️ The #discovery of the Big Ring, the second uLSS found in MgII-absorber catalogues, following the previously reported Giant Arc, is now posted on #arXiv and submitted to #JCAP by @morninglopez, @rgclowes, and G.M. Williger
https://arxiv.org/abs/2402.07591

#cosmology #bigring #giantarc #galaxies #astrodon #science #STEM #news

Check out Dr Becky Smethurst's latest Night Sky News #video, wherein she reviews the #discovery of the #BigRing of #galaxies (feat. @morninglopez) and a series of #JWST papers ruling out a likely culprit of the #HubbleTension (feat. @gdanandofficial)

https://youtu.be/3NeKR7bqolY

#cosmology #astronomy #astrophysics #astrodon #news #drbecky #drbeckysmethurst #youtube #youtuber #scicomm #science #communication #sciencecommunication #space #research #giantarc #quasars #southpolewall #nasa #physics

The ingredients of a cosmological mystery: Big Ring, Giant Arc, Sloan Great Wall, South Pole Wall, Clowes-Campusano Large Quasar Group, Laniakea Supercluster, the dark flow, Sir Roger Penrose's Conformal Cyclic Cosmology, cosmic strings, ...
https://www.space.com/big-ring-galactic-superstructure-celestial-anomaly

#cosmology #bigring #giantarc #sloangreatwall #southpolewall #ClowesCampeanoLQG #quasars #laniakea #supercluster #laniakeasupercluster #galaxies #darkflow #penrose #rogerpenrose #CCC #cycliccosmology #cosmicstrings #astronomy #space