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#cosmological

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Daniel Fischer

21cm Intensity Mapping cross-correlation with #galaxy surveys - current and forecasted cosmological parameters estimation for the #SKAO: arxiv.org/abs/2309.00710 -> Separating the cosmic wheat from the chaff: astrobites.org/2023/11/27/21cm - #cosmological parameter estimation with the 21-cm line

arXiv.org21cm Intensity Mapping cross-correlation with galaxy surveys: current and forecasted cosmological parameters estimation for the SKAOWe present a comprehensive set of forecasts for the cross-correlation signal between 21cm intensity mapping and galaxy redshift surveys. We focus on the data sets that will be provided by the SKAO for the 21cm signal, DESI and Euclid for galaxy clustering. We build a likelihood which takes into account the effect of the beam for the radio observations, the Alcock-Paczynski effect, a simple parameterization of astrophysical nuisances, and fully exploit the tomographic power of such observations in the range $z=0.7-1.8$ at linear and mildly non-linear scales ($k<0.25 h/$Mpc). The forecasted constraints, obtained with Monte Carlo Markov Chains techniques in a Bayesian framework, in terms of the six base parameters of the standard $Λ$CDM model, are promising. The predicted signal-to-noise ratio for the cross-correlation can reach $\sim 50$ for $z\sim 1$ and $k\sim 0.1 h/$ Mpc. When the cross-correlation signal is combined with current Cosmic Microwave Background (CMB) data from Planck, the error bar on $Ω_{\rm c}\,h^2$ and $H_0$ is reduced by a factor 3 and 6, respectively, compared to CMB only data, due to the measurement of matter clustering provided by the two observables. The cross-correlation signal has a constraining power that is comparable to the auto-correlation one and combining all the clustering measurements a sub-percent error bar of 0.33% on $H_0$ can be achieved, which is about a factor 2 better than CMB only measurement. Finally, as a proof-of-concept, we test the full pipeline on the real data measured by the MeerKat collaboration (Cunnington et al. 2022) presenting some (weak) constraints on cosmological parameters.
Daniel Fischer

The #FLAMINGO project: #cosmological hydrodynamical #simulations for large-scale structure and galaxy cluster surveys / Calibrating large cosmological hydrodynamical simulations with machine learning / revisiting the S8 tension and the role of baryonic physics: academic.oup.com/mnras/article / academic.oup.com/mnras/advance / academic.oup.com/mnras/advance -> Astronomers carry out largest ever cosmological computer simulation: ras.ac.uk/news-and-press/news/

Mikko Tuomi

The consensus is that any laboratory #mass must be attracted by the Earth, although some authors have considered the #cosmological consequences if #antimatter should be repelled by #matter.

In the general theory of relativity, the weak equivalence principle requires that all masses react identically to #gravity.

Here we show that #antihydrogen atoms behave in a way consistent with gravitational attraction to the Earth.

Repulsive #antigravity is ruled out.

#physics
nature.com/articles/s41586-023

NatureObservation of the effect of gravity on the motion of antimatter - NatureMagnetically confined neutral antihydrogen atoms released in a gravity field were found to fall towards Earth like ordinary matter, in accordance with Einstein’s general theory of relativity.
Daniel Fischer

Evidence for suppression of structure growth in the concordance #cosmological model: arxiv.org/abs/2302.01331 -> The #universe caught suppressing cosmic #structure growth: news.umich.edu/the-universe-ca

arXiv.orgEvidence for suppression of structure growth in the concordance cosmological modelWe present evidence for a suppressed growth rate of large-scale structure during the dark-energy dominated era. Modeling the growth rate of perturbations with the ``growth index'' $γ$, we find that current cosmological data strongly prefer a higher growth index than the value $γ=0.55$ predicted by general relativity in a flat $Λ$CDM cosmology. Both the cosmic microwave background data from Planck and the large-scale structure data from weak lensing, galaxy clustering, and cosmic velocities separately favor growth suppression. When combined, they yield $γ=0.633^{+0.025}_{-0.024}$, excluding $γ=0.55$ at a statistical significance of 3.7$σ$. The combination of $fσ_8$ and Planck measurements prefers an even higher growth index of $γ=0.639^{+0.024}_{-0.025}$, corresponding to a 4.2$σ$-tension with the concordance model. In Planck data, the suppressed growth rate offsets the preference for nonzero curvature and fits the data equally well as the latter model. A higher $γ$ leads to a higher matter fluctuation amplitude $S_8$ inferred from galaxy clustering and weak lensing measurements, and a lower $S_8$ from Planck data, effectively resolving the $S_8$ tension.
Continued thread
Daniel Fischer

Constraints on the #HubbleConstant from #SupernovaRefsdal's reappearance: arxiv.org/abs/2305.06367 - the result of 67(+/-4) km/s/Mpc is in hard conflict with numerous other methods that cluster around 74(+/- a few) but funnily in accordance with determinations from the CMBR. So the famous tension re. this most fundamental #cosmological number, which is turning 10 years old this year, is getting more intriguing than ever ...

arXiv.orgConstraints on the Hubble constant from Supernova Refsdal's reappearanceThe gravitationally lensed Supernova Refsdal appeared in multiple images, produced through gravitational lensing by a massive foreground galaxy cluster. After the supernova appeared in 2014, lens models of the galaxy cluster predicted an additional image of the supernova would appear in 2015, which was subsequently observed. We use the time delays between the images to perform a blinded measurement of the expansion rate of the Universe, quantified by the Hubble constant (H0). Using eight cluster lens models, we infer H0 = 64.8 +4.4-4.3 km / s / Mpc, where Mpc is the megaparsec. Using the two models most consistent with the observations, we find H0 = 66.6 +4.1-3.3 km / s / Mpc. The observations are best reproduced by models that assign dark-matter halos to individual galaxies and the overall cluster.
Daniel Fischer

No Tension - #JWST #Galaxies at z>10 Consistent with #Cosmological Simulations: arxiv.org/abs/2304.13755 - "we use results from the Renaissance simulations, which are a suite of high resolution simulations designed to model galaxy formation in the early universe. We find that the most massive galaxies in Renaissance have stellar masses and star formation rates that are entirely consistent with the observations from the JADES and CEERS surveys."

arXiv.orgNo Tension: JWST Galaxies at $z > 10$ Consistent with Cosmological SimulationsRecent observations by JWST have uncovered galaxies in the very early universe via the JADES and CEERS surveys. These galaxies have been measured to have very high stellar masses with substantial star formation rates. There are concerns that these observations are in tension with the $Λ$CDM model of the universe, as the stellar masses of the galaxies are relatively high for their respective redshifts. Recent studies have compared the JWST observations with large-scale cosmological simulations. While they were successful in reproducing the galaxies seen in JADES and CEERS, the mass and spatial resolution of these simulations were insufficient to fully capture the early assembly history of the simulated galaxies. In this study, we use results from the Renaissance simulations, which are a suite of high resolution simulations designed to model galaxy formation in the early universe. We find that the most massive galaxies in Renaissance have stellar masses and star formation rates that are entirely consistent with the observations from the JADES and CEERS surveys. The exquisite resolution afforded by Renaissance allows us to model the build-up of early galaxies from stellar masses as low as 10$^4$ M$_\odot$ up to a maximum stellar mass of a few times 10$^{7}$ M$_\odot$. Within this galaxy formation paradigm, we find excellent agreement with JADES and CEERS. We find no tension between the $Λ$CDM model and current JWST measurements. As JWST continues to explore the high redshift universe, high resolution simulations, such as Renaissance, will continue to be crucial in understanding the formation history of early embryonic galaxies.
Prof Felipe Gusmao

150 (or so) Arguments for #Atheism

"A popular view in contemporary #analytic #philosophy of #religion is that while there are many arguments for #theism -- #cosmological, #ontological, and #teleological arguments; #moral arguments; arguments from #consciousness; etc. (...) -- there are only one or two arguments for atheism, viz., the problem of #evil and (more recently) the argument from #divine hiddenness.

This is a misconception. Here are well over 150"

exapologist.blogspot.com/2022/

@philosophy

exapologist.blogspot.com150 (or so) Arguments for AtheismA popular view in contemporary analytic philosophy of religion is that while there are many arguments for theism -- cosmological, ontologica...
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