#darkenergy — Public Fediverse posts

The Beginnings of Man -Part 1

The nature of Man has evolved over millions of years, changed by environmental conditions, by the response of his instinctual nature and by the actions of his ego. Man’s inner characteristics are altogether different from the ancestral root which governs other species. Why then is he so different?

https://tonyaholisticblog.com/2026/08/31/the-beginnings-of-man-part-1/

Weekly Update from the Open Journal of Astrophysics – 23/05/2026

It’s Saturday once again, so time for another update of activity at the Open Journal of Astrophysics. Since the last update we have published a further six papers, bringing the number in Volume 9 (2026) to 110 and the total so far published by OJAp up to 558.

I will continue to include the posts made on our Mastodon account (on Fediscience); these announcements also show the DOI for each paper.

The first paper to report this week, published on Monday 18th May in the folder Instrumentation and Methods for Astrophysics is “Edges In Coadded Images” by Erin Sheldon (Brookhaven National Laboratory, USA). This paper describes a study exploring how image discontinuities and noise impact weak gravitational lensing measurements, finding no significant biases under typical conditions. Biases occur only in extreme cases, but can be mitigated.

The overlay for this paper is here

You can find the officially accepted version on arXiv here and the announcement on Fediverse here:

https://fediscience.org/@OJ_Astro/116594222032390191

The second paper for this week, also published on Monday 18th May but in the folder Cosmology and Nongalactic Astrophysics, is “Joint cosmological fits to DESI-DR1 full-shape clustering and weak gravitational lensing in configuration space” by A. Semenaite (Swinburne Institute of Technology, Australia) and 72 other authors from all round the world. This paper presents a cosmological analysis of correlations between the DESI-DR1 Bright Galaxy Survey and Luminous Red Galaxy samples and overlapping shear measurements from various weak lensing surveys.

The overlay for this one is here:

The official version of the paper can be found on arXiv here and the Fediverse announcement here:

https://fediscience.org/@OJ_Astro/116594256215421009

Next one up, the third paper of the week, and the third published on Monday 18th May, and in the folder Cosmology and Nongalactic Astrophysics is “Probing Dark Energy Microphysics with kSZ Tomography” by Julius Adolff, Selim Hotinli and Neal Dalal (all of the Perimeter Institute, Canada). This paper explores how kinetic Sunyaev-Zel’dovich tomography and galaxy clustering can enhance our understanding of dark energy and its effects, potentially revealing its microphysical properties in future surveys.

The overlay for this one is here:

The final, accepted version can be found on arXiv here and the Mastodon announcement is here:

https://fediscience.org/@OJ_Astro/116594304124291605

The fourth paper this week, published on Wednesday May 20th is “A Census of Variable Radio Sources at 3 GHz” by Yjan A. Gordon, Peter S. Ferguson, Michael N. Martinez and Eric J. Hooper (all of the University of Wisconsin, USA). This article, published in the folder Astrophysics of Galaxies, uses data from the Very Large Array Sky Survey to analyze variability in the radio sky, finding most changes consistent with blazars and quasars.

The overlay is here:

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

https://fediscience.org/@OJ_Astro/116607468481260244

The fifth article of this week was published on Friday 22nd May in the folder Instrumentation and Methods for Astrophysics. The title is “Uncovering the Next Galactic Supernova with the Vera C. Rubin Observatory” by John Banovetz (Lawrence Berkeley Lab., USA), Claire-Alice Hebert & Peter B. Denton (Brookhaven National Lab., USA), Dan Scolnic (Duke University, USA), Anze Slosar (Brookhaven) and Chris Walter (Duke). The paper presents a study simulating how effectively the Vera C. Rubin Observatory can localize supernovae using neutrino triggers, finding a 57-97% success rate based on stellar mass density predictions.

The overlay is here:

You can find the authorized version of this paper on arXiv here and the Fediverse announcement is here:

https://fediscience.org/@OJ_Astro/116617293753093751

Last, but by no means least, this week we have “Pulsar timing solutions for 17 pulsars at 150 MHz from the Irish LOFAR station” by David J. McKenna (ASTRON, The Netherlands), Evan F. Keane (Trinity College Dublin, Ireland), Peter T. Gallagher (DIAS, Ireland) and Joe McCauley (Trinity). This was published on Friday 22nd May in the folder High-Energy Astrophysical Phenomena. It presents a demonstration of the use of international Low Frequency Array (LOFAR) stations in tracking and characterizing pulsars, providing new insights into these neutron stars’ emission properties.

The overlay for this one is here:

You can find the authorized version of this paper on arXiv here and the Fediverse announcement is here:

https://fediscience.org/@OJ_Astro/116617404344791486

And that concludes this week’s update. I’ll do another one next Saturday.

#arXiv250800976v2 #arXiv250906929v3 #arXiv251105653v2 #arXiv251215961v2 #arXiv260112094v2 #arXiv260522516v1 #AstrophysicsOfGalaxies #blazars #cosmicShear #cosmologicalSimulations #CosmologyAndNonGalacticAstrophysics #DarkEnergy #DarkEnergySpectroscopicInstrument #DarkEnergySurvey #DiamondOpenAccess #DiamondOpenAccessPublishing #galaxyClustering #HighEnergyAstrophysicalPhenomena #InstrumentationAndMethodsForAstrophysics #kineticSunyaevZeDovichEffect #LOFAR #OpenAccess #OpenAccessPublishing #PointSpreadFunction #pulsars #quasars #radioAstronomy #stackedImages #SunyaevZeDovichEffect #supernova #supernovae #Tomography #VeraCRubinObservatory #VeryLargeArray #weakGravitationalLensing

Weekly Update from the Open Journal of Astrophysics – 23/05/2026

It’s Saturday once again, so time for another update of activity at the Open Journal of Astrophysics. Since the last update we have published a further six papers, bringing the number in Volume 9 (2026) to 110 and the total so far published by OJAp up to 558.

I will continue to include the posts made on our Mastodon account (on Fediscience); these announcements also show the DOI for each paper.

The first paper to report this week, published on Monday 18th May in the folder Instrumentation and Methods for Astrophysics is “Edges In Coadded Images” by Erin Sheldon (Brookhaven National Laboratory, USA). This paper describes a study exploring how image discontinuities and noise impact weak gravitational lensing measurements, finding no significant biases under typical conditions. Biases occur only in extreme cases, but can be mitigated.

The overlay for this paper is here

You can find the officially accepted version on arXiv here and the announcement on Fediverse here:

https://fediscience.org/@OJ_Astro/116594222032390191

The second paper for this week, also published on Monday 18th May but in the folder Cosmology and Nongalactic Astrophysics, is “Joint cosmological fits to DESI-DR1 full-shape clustering and weak gravitational lensing in configuration space” by A. Semenaite (Swinburne Institute of Technology, Australia) and 72 other authors from all round the world. This paper presents a cosmological analysis of correlations between the DESI-DR1 Bright Galaxy Survey and Luminous Red Galaxy samples and overlapping shear measurements from various weak lensing surveys.

The overlay for this one is here:

The official version of the paper can be found on arXiv here and the Fediverse announcement here:

https://fediscience.org/@OJ_Astro/116594256215421009

Next one up, the third paper of the week, and the third published on Monday 18th May, and in the folder Cosmology and Nongalactic Astrophysics is “Probing Dark Energy Microphysics with kSZ Tomography” by Julius Adolff, Selim Hotinli and Neal Dalal (all of the Perimeter Institute, Canada). This paper explores how kinetic Sunyaev-Zel’dovich tomography and galaxy clustering can enhance our understanding of dark energy and its effects, potentially revealing its microphysical properties in future surveys.

The overlay for this one is here:

The final, accepted version can be found on arXiv here and the Mastodon announcement is here:

https://fediscience.org/@OJ_Astro/116594304124291605

The fourth paper this week, published on Wednesday May 20th is “A Census of Variable Radio Sources at 3 GHz” by Yjan A. Gordon, Peter S. Ferguson, Michael N. Martinez and Eric J. Hooper (all of the University of Wisconsin, USA). This article, published in the folder Astrophysics of Galaxies, uses data from the Very Large Array Sky Survey to analyze variability in the radio sky, finding most changes consistent with blazars and quasars.

The overlay is here:

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

https://fediscience.org/@OJ_Astro/116607468481260244

The fifth article of this week was published on Friday 22nd May in the folder Instrumentation and Methods for Astrophysics. The title is “Uncovering the Next Galactic Supernova with the Vera C. Rubin Observatory” by John Banovetz (Lawrence Berkeley Lab., USA), Claire-Alice Hebert & Peter B. Denton (Brookhaven National Lab., USA), Dan Scolnic (Duke University, USA), Anze Slosar (Brookhaven) and Chris Walter (Duke). The paper presents a study simulating how effectively the Vera C. Rubin Observatory can localize supernovae using neutrino triggers, finding a 57-97% success rate based on stellar mass density predictions.

The overlay is here:

You can find the authorized version of this paper on arXiv here and the Fediverse announcement is here:

https://fediscience.org/@OJ_Astro/116617293753093751

Last, but by no means least, this week we have “Pulsar timing solutions for 17 pulsars at 150 MHz from the Irish LOFAR station” by David J. McKenna (ASTRON, The Netherlands), Evan F. Keane (Trinity College Dublin, Ireland), Peter T. Gallagher (DIAS, Ireland) and Joe McCauley (Trinity). This was published on Friday 22nd May in the folder High-Energy Astrophysical Phenomena. It presents a demonstration of the use of international Low Frequency Array (LOFAR) stations in tracking and characterizing pulsars, providing new insights into these neutron stars’ emission properties.

The overlay for this one is here:

You can find the authorized version of this paper on arXiv here and the Fediverse announcement is here:

https://fediscience.org/@OJ_Astro/116617404344791486

And that concludes this week’s update. I’ll do another one next Saturday.

#arXiv250800976v2 #arXiv250906929v3 #arXiv251105653v2 #arXiv251215961v2 #arXiv260112094v2 #arXiv260522516v1 #AstrophysicsOfGalaxies #blazars #cosmicShear #cosmologicalSimulations #CosmologyAndNonGalacticAstrophysics #DarkEnergy #DarkEnergySpectroscopicInstrument #DarkEnergySurvey #DiamondOpenAccess #DiamondOpenAccessPublishing #galaxyClustering #HighEnergyAstrophysicalPhenomena #InstrumentationAndMethodsForAstrophysics #kineticSunyaevZeDovichEffect #LOFAR #OpenAccess #OpenAccessPublishing #PointSpreadFunction #pulsars #quasars #radioAstronomy #stackedImages #SunyaevZeDovichEffect #supernova #supernovae #Tomography #VeraCRubinObservatory #VeryLargeArray #weakGravitationalLensing

Timescape versus Dark Energy?

Just before the Christmas break I noticed a considerable amount of press coverage claiming that Dark Energy doesn’t exist. Much of the media discussion is closely based on a press release produced by the Royal Astronomical Society. Despite the excessive hype, and consequent initial scepticism, I think there are some interesting issues.

The main focus of the discussion is a paper (available on arXiv here) by Seifert et al. with the title Supernovae evidence for foundational change to cosmological models. This paper is accompanied by a longer article called Cosmological foundations revisited with Pantheon+ (also available on arXiv) by a permutation of the same authors, which goes into more detail about the analysis of supernova observations. If you want some background, the “standard” Pantheon+ supernova analysis is described in this paper. The reanalysis presented in the recent papers is motivated an idea called the Timescape model, which is not new. It was discussed by David Wiltshire (one of the authors of the recent papers) in 2007 here and in a number of subsequent papers; there’s also a long review article by Wiltshire here (dated 2013).

So what’s all the fuss about?

Simulation of the Cosmic Web

In the standard cosmological model we assume that, when sufficiently coarse-grained, the Universe obeys the Cosmological Principle, i.e. that it is homogeneous and isotropic. This implies that the space-time is described by a Friedmann–Lemaître–Robertson–Walker metric (FLRW) metric. Of course we know that the Universe is not exactly smooth. There is a complex cosmic web of galaxies, filaments, clusters, and giant voids which comprise the large-scale structure of the Universe. In the standard cosmological model these fluctuations are treated as small perturbations on a smooth background which evolve linearly on large scales and don’t have a significant effect on the global evolution of the Universe.

This standard model is very successful in accounting for many things but only at the expense of introducing dark energy whose origin is uncertain but which accounts for about 70% of the energy density of the Universe. Among other things, this accounts for the apparent acceleration of the Universe inferred from supernovae measurements.

The standard cosmology’s energy budget

The approach taken in the Timescape model is to dispense with the FLRW metric, and the idea of separating the global evolution from the inhomogeneities. The idea instead is that the cosmic structure is essentially non-linear so there is no “background metric”. In this model, cosmological observations can not be analysed within the standard framework which relies on the FLRW assumption. Hence the need to reanalyse the supernova data. The name Timescape refers to the presence of significant gravitational time-dilation effects in this model as distinct from the standard model.

I wrote before in the context of a different paper:

….the supernovae measurements do not directly measure cosmic acceleration. If one tries to account for them with a model based on Einstein’s general relativity and the assumption that the Universe is on large-scales is homogeneous and isotropic and with certain kinds of matter and energy then the observations do imply a universe that accelerates. Any or all of those assumptions may be violated (though some possibilities are quite heavily constrained). In short we could, at least in principle, simply be interpreting these measurements within the wrong framework…

So what to make of the latest papers? I have to admit that I didn’t follow all the steps of the supernova reanalysis. I hope an expert can comment on this! I will therefore restrict myself to some general comments.

• My attitude to the standard cosmological model is that it is simply a working hypothesis and we should not elevate it to a status any higher than that. It is based not only on the Cosmological Principle (which could be false), but on the universal applicability of general relativity (which might not be true), and on a number of other assumptions that might not be true either.
• It is important to recognize that one of the reasons that the standard cosmology is the front-runner is that it provides a framework that enables relatively straightforward prediction and interpretation of cosmological measurements. That goes not only for supernova measurements but also for the cosmic microwave background, galaxy clustering, gravitational lensing, and so on. This is much harder to do accurately in the Timescape model simply because the equations involved are much more complex; there are few exact solutions of Einstein’s equations that can help. It is important that people work on alternatives such as this.
• Second, the idea that inhomogeneities might be much more important than assumed in the standard model has been discussed extensively in the literature over the last twenty years or so under the heading “backreaction”. My interpretation of the current state of play is that there are many unresolved questions, largely because of technical difficulties. See, for example, work by Thomas Buchert (here and, with many other collaborators here) and papers by Green & Wald (here and here). Nick Kasiser also wrote about it here.
• The new papers under discussion focus entirely on supernovae measurements. It must be recognized that these provide just one of the pillars supporting the standard cosmology. Over the years, many alternative models have been suggested that claim to “fix” some alleged problem with cosmology only to find that it makes other issues worse. That’s not a reason to ignore departures from the standard framework, but it is an indication that we have a huge amount of data and we’re not allowed to cherry-pick what we want. We have to fit it all. The strongest evidence in favour of the FLRW framework actually comes from the cosmic microwave background (CMB) with the supernovae provide corroboration. I would need to see a detailed prediction of the anisotropy of the CMB before being convinced.
• The Timescape model is largely based on the non-linear expansion of cosmic voids. These are undoubtedly important, and there has been considerable observational and theoretical activity in understanding them and their evolution in the standard model. It is not at all obvious to me that the voids invoked to explain the apparent acceleration of the Universe are consistent with what we actually see in our surveys. That is something else to test.
• Finally, the standard cosmology includes a prescription for the initial conditions from which the present inhomogeneities grew. Where does the cosmic web come from in the Timescape model?

Anyway, I’m sure there’ll be a lot of discussion of this in the next few weeks as cosmologists return to the Universe from their Christmas holidays!

Comments are welcome through the box below, especially from people who have managed to understand the cos.

#arXiv241215143 #CosmicWeb_ #cosmologicalPrinciple #DarkEnergy #Pantheon #supernovae #Timescape #timescapeModel