Podcasts about lambda cdm

In this exclusive interview, Professor Mario Jurić reveals how the Vera Rubin Observatory accidentally discovered 2,000 asteroids in just 10 hours while testing its capabilities on the distant Virgo Cluster—transforming humanity's asteroid discovery rate from 20,000 per year globally to potentially over one million annually with a single telescope. Jurić explains how VRO's revolutionary multi-messenger astronomy capabilities will detect dark matter's effects and light simultaneously, automatically slewing to capture cosmic catastrophes like black hole collisions within 30 seconds of detection. From mapping dark matter in galaxy clusters 54 million light-years away to building Earth's first comprehensive planetary defense system against asteroid impacts, this conversation explores how one observatory is about to fundamentally change both our understanding of the universe and our ability to survive in it. — Please join my mailing list here

How half of the normal matter in the universe is finally confirmed to exist, not that most of us knew it wasn't. Also, why the next big collider should be muon-muon, and a spider that hangs out around underwater methane seeps.The universe is thought to consist of 70% Dark Energy, 25% Dark Matter, and just 5% Baryonic matter which is the atoms that make up you and me. At least, that's what the models suggest. But a well-kept secret between astronomers and cosmologists for all these years has been that they haven't actually ever seen almost half of that 5% normal matter because it is thinly dispersed as gas between the galaxies and galactic clusters. This week, two studies have been published putting that right.Satisfactory model-match #1: Liam Connor of Harvard University with colleagues from Caltech have been using a mysterious phenomenon called Fast Radio Bursts (FBRs) to infer what the intergalactic medium is in between, and how much of it there is. Satisfactory model-match #2: Konstanios Migkas of Leiden University and colleagues have been looking at the very faint x-ray signal from the intergalactic medium, removing the incidental x-ray sources such as black holes, and have managed to identify some structure - in this case a mind-bendingly huge filament of ionised gas stretching between two galactic superclusters - confirming the state of “Warm Hot Intergalactic Medium” (WHIM) as predicted for much of the universe.Of course, there is not just the cosmological standard model (lambdaCDM) that these satisfy in science today. There is also the remarkably resilient Standard Model of particle physics. A report this week from the US National Academies recommends the US begins building the world's next particle collider to follow the work of the LHC (and FCC) at Cern. It should, as University of Tennessee at Knoxville's Tova Holmes tells us, collide not ordinary, stable, easy to manipulate particles like protons and electrons, but muons. Finally, Shana Goffredi of Occidental College in California, has found a VERY odd spider. Diving to depths in the submersible Alvin, they have found that a species of small sea-spiders, Sericosura, actually farm bacteria on their exoskeleton. Why? Because they hang around methane seeps on the ocean floor, where a specialist bacteria can metabolize methane – something the spiders themselves can't do. Not only do the spiders then graze on the bacteria they carry around, they even pass samples of the bacteria onto their offspring by leaving bacterial lunch-boxes in their egg-sacs.Presenter: Roland Pease Producer: Alex Mansfield, with Sophie Ormiston Production Coordinator: Jasmine Cerys GeorgePhoto Credit: Jack Madden, IllustrisTNG, Ralf Konietzka, Liam Connor/CfA

Is everything we thought we knew about the universe… wrong? Lambda-CDM model nearing its breaking point? Could dark energy actually be evolving? In this episode of Into the Impossible, I'm joined by Kyle Dawson and Daniel Green to discuss the latest data from the DESI experiment. These new results are making headlines, and rightfully so, as they hold the potential to transform our understanding of the universe completely.  Kyle Dawson, a key figure in the DESI project and professor at the University of Utah, explains the findings from DESI's second data release. Together with Daniel Green from the University of California, San Diego, we dig into how fresh observations of dark energy, baryon acoustic oscillations (BAO), and cosmic expansion are revealing cracks in the standard model. We also break down the implications of these results and talk about the possible existence of negative neutrino masses—a topic that's been gaining a lot of attention in the cosmology community. Don't miss out!  — Please join my mailing list here

(0:24) Non está documentado que Einstein dixera que a introdución do termo cosmolóxico fora a maior metida de zoca da súa vida. Pero a súa constante cosmolóxica é, ata o de agora, unha chave de bóveda do que sabemos do universo. (6:11) O noso ornitólogo Nacho Munilla explícanos o papel recentemente descuberto da biofluorescencia das aves do paraíso. (20:54) Efeméride do 20 de marzo do Calendario da Historia da Ciencia de Moncho Núñez. (23:08) Os datos liberados hoxe pola colaboración DESI (Dark Energy Spectroscopic Instrument) no encontro anual da American Physical Society apuntan a que a enerxía escura non é unha constante, senón que vai devalando na historia do universo. Isto podería rachar co actual modelo estándar cosmolóxico Lambda CDM. Nolo debulla o investigador da Universidade de Berkeley Antón Baleato Lizarcos.

Shoot, someone made the mistake of letting Cole pick the episode topic. In this episode, Cole, Cormac, and Shashank talk about the big boy on cosmology campus: Lambda CDM. This model has gotten a bit too big for its britches we think: what are the things about the universe that this model can't explain? Shashank gives us a tour through the dark matter hearts of galaxies which don't match up with cosmological predictions and Cormac shows us how 1500 (ish? We're not clear on this one.) supernovae could hint at a fundamental flaw in Lambda CDM.   Astrobites: Testing cosmology with the DES 5-year supernovae dataset: https://astrobites.org/2024/03/22/template-post-21/   Digging into the Core: Dark Matter and Dwarf Galaxies https://astrobites.org/2015/07/14/digging-into-the-core-dark-matter-and-dwarf-galaxies/   Space Sound: Listen to the hum of NANOGrav's gravitational wave background https://www.youtube.com/watch?v=nGO0wQK9ns4

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La historia de la teoría del Big Bang es larga y muy cambiante. Hoy día la teoría clásica del Big Bang está más que descartada y, en su lugar, hoy tenemos el modelo Lambda-CDM. Una de las piezas clave de este modelo es la inflación, un proceso teórico por el cual el universo sufrió una expansión extremadamente rápida y repentina. Este proceso resuelve algunos problemas de la toería del Big Bang caliente, como el problema del horizonte o el problema de la planitud. En este capítulo abordamos en profundidad la inflación. En las noticias, un grano de polvo encontrado en la Antártida arroja información sobre una supernova ocurrida antes de la formación del Sol, el EHT revela una nueva imagen del agujero negro supermasivo Sagitario A* y un nuevo estudio propone utilizar la fase de gigante roja de algunas estrellas como candelas estándar para medir distancias en el cosmos. 3, 2, 1... ¡Despegamos!

Das Lambda-CDM-Modell beschreibt wie sich das gesamte Universum vom Urknall bis heute entwickelt hat. Es ist eigentlich erstaunlich, dass es so eine Theorie gibt, aber es gibt sie und was sie aussagt, erfahrt ihr in der neuen Folge der Sternengeschichten. Wer den Podcast finanziell unterstützen möchte, kann das hier tun: Mit PayPal (https://www.paypal.me/florianfreistetter), Patreon (https://www.patreon.com/sternengeschichten) oder Steady (https://steadyhq.com/sternengeschichten)

The so-called Crisis in Cosmology didn't go anywhere. Different methods are giving different values for the Hubble Constant creating one of the most interesting mysteries in Astronomy. What possible solutions do we have? Discussing them with Dr Sunny Vagnozzi.

Eerder dit jaar verscheen er een foto van de James Webb ruimtetelescoop die het huidige kosmologische model (Lambda CDM) doet wankelen. Is het werkelijk tijd om de handdoek in de ring te gooien? Uiteraard niet! De sloomste podcaster van het heelal legt de feiten voor u op een rijtje. CEERS:https://ceers.github.io/JWST NIRSpec camera:https://jwst-docs.stsci.edu/jwst-near-infrared-spectrographStellar Initial Mass Function Varies with Metallicities and Time:https://arxiv.org/pdf/2301.07029.pdfEvidence for Initial Mass Function Variation in Massive Early-Type Galaxies:https://www.annualreviews.org/doi/abs/10.1146/annurev-astro-032620-020217JWST's "too massive" galaxy problem solved?! | A non-universal IMF (Dr. Becky):https://www.youtube.com/watch?v=W4KH1Jw6HBIStress Testing ΛCDM with High-redshift Galaxy Candidates:https://arxiv.org/abs/2208.01611Initial Mass Function:https://en.wikipedia.org/wiki/Initial_mass_functionDe Zimmerman en Space podcast is gelicenseerd onder een Creative Commons CC0 1.0 licentie.http://creativecommons.org/publicdomain/zero/1.0

Ethan Siegel is a theoretical astrophysicist and science communicator. He received his PhD from the University of Florida and held academic positions at the University of Arizona, University of Oregon, and Lewis & Clark College before moving on to become a full-time science writer. Ethan is the author of the book Beyond The Galaxy, which is the story of “How Humanity Looked Beyond Our Milky Way And Discovered The Entire Universe” and he has contributed numerous articles to ScienceBlogs, Forbes, and BigThink. Today, Ethan is the face and personality behind Starts With A Bang, both a website and podcast by the same name that is dedicated to explaining and exploring the deepest mysteries of the cosmos. In this episode, Ethan and I discuss the mysterious nature of dark matter: the evidence for it and the proposals for what it might be. Patreon: https://www.patreon.com/timothynguyen Part I. Introduction 00:00:00 : Biography and path to science writing 00:07:26 : Keeping up with the field outside academia 00:11:42 : If you have a bone to pick with Ethan... 00:12:50 : On looking like a scientist and words of wisdom 00:18:24 : Understanding dark matter = one of the most important open problems 00:21:07 : Technical outline Part II. Ordinary Matter 23:28 : Matter and radiation scaling relations 29:36 : Hubble constant 31:00 : Components of rho in Friedmann's equations 34:14 : Constituents of the universe 41:21 : Big Bang nucleosynthesis (BBN) 45:32 : eta: baryon to photon ratio and deuterium formation 53:15 : Mass ratios vs eta Part III. Dark Matter 1:01:02 : rho = radiation + ordinary matter + dark matter + dark energy 1:05:25 : nature of peaks and valleys in cosmic microwave background (CMB): need dark matter 1:07:39: Fritz Zwicky and mass mismatch among galaxies of a cluster 1:10:40 : Kent Ford and Vera Rubin and and mass mismatch within a galaxy 1:11:56 : Recap: BBN tells us that only about 5% of matter is ordinary 1:15:55 : Concordance model (Lambda-CDM) 1:21:04 : Summary of how dark matter provides a common solution to many problems 1:23:29 : Brief remarks on modified gravity 1:24:39 : Bullet cluster as evidence for dark matter 1:31:40 : Candidates for dark matter (neutrinos, WIMPs, axions) 1:38:37 : Experiment vs theory. Giving up vs forging on 1:48:34 : Conclusion Image Credits: http://timothynguyen.org/image-credits/ Further learning: E. Siegel. Beyond the Galaxy Ethan Siegel's webpage: www.startswithabang.com   More Ethan Siegel & Timothy Nguyen videos: Brian Keating's Losing the Nobel Prize Makes a Good Point but … https://youtu.be/iJ-vraVtCzw Testing Eric Weinstein's and Stephen Wolfram's Theories of Everything https://youtu.be/DPvD4VnD5Z4   Twitter: @iamtimnguyen Webpage: http://www.timothynguyen.org

The diversity of rotation curves of simulated galaxies with cusps and cores by Finn A. Roper et al. on Wednesday 30 November We use $Lambda$CDM cosmological hydrodynamical simulations to explore the kinematics of gaseous discs in late-type dwarf galaxies. We create high-resolution 21-cm 'observations' of simulated dwarfs produced in two variations of the EAGLE galaxy formation model: one where supernova-driven gas flows redistribute dark matter and form constant-density central 'cores', and another where the central 'cusps' survive intact. We 'observe' each galaxy along multiple sight lines and derive a rotation curve for each observation using a conventional tilted-ring approach to model the gas kinematics. We find that the modelling process introduces systematic discrepancies between the recovered rotation curve and the actual circular velocity curve driven primarily by (i) non-circular gas orbits within the discs; (ii) the finite thickness of gaseous discs, which leads to overlap of different radii in projection; and (iii) departures from dynamical equilibrium. Dwarfs with dark matter cusps often appear to have a core, whilst the inverse error is less common. These effects naturally reproduce an observed trend which other models struggle to explain: late-type dwarfs with more steeply-rising rotation curves appear to be dark matter-dominated in the inner regions, whereas the opposite seems to hold in galaxies with core-like rotation curves. We conclude that if similar effects affect the rotation curves of observed dwarfs, a late-type dwarf population in which all galaxies have sizeable dark matter cores is most likely incompatible with current measurements. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2203.16652v3

Mirror Dark Sector Solution of the Hubble Tension with Time-varying Fine-structure Constant by John Zhang et al. on Wednesday 30 November We explore a model introduced by Cyr-Racine, Ge, and Knox (arXiv:2107.13000(2)) that resolves the Hubble tension by invoking a ``mirror world" dark sector with energy density a fixed fraction of the ``ordinary" sector of Lambda-CDM. Although it reconciles cosmic microwave background and large-scale structure observations with local measurements of the Hubble constant, the model requires a value of the primordial Helium mass fraction that is discrepant with observations and with the predictions of Big Bang Nucleosynthesis (BBN). We consider a variant of the model with standard Helium mass fraction but with the value of the electromagnetic fine-structure constant slightly different during photon decoupling from its present value. If $alpha$ at that epoch is lower than its current value by $Delta alpha simeq -2times 10^{-5}$, then we can achieve the same Hubble tension resolution as in Cyr-Racine, et al. but with consistent Helium abundance. As an example of such time-evolution, we consider a toy model of an ultra-light scalar field, with mass $m

A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Wednesday 30 November Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $zsim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Omega_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Lambda$CDM model with $Omega_M = 0.3$ and $H_0 = 70 , mathrm{km,s^{-1},Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v2

Updating constraints on phantom crossing f T gravity by F. B. M. dos Santos. on Wednesday 30 November We establish constraints on $f(T)$ gravity by considering the possibility of a scenario that supports a phantom crossing of the equation of state parameter $w_{DE}$. After determining the viable parameter space of the model, while checking the impact on the background dynamics, we perform an analysis to obtain constraints on cosmological parameters and determine the viability of this scenario. To this end, we use combined data sets from cosmic chronometers (CC), baryonic acoustic oscillations (BAO), redshift space measurements (RSD), cosmic microwave background (CMB) and Big Bang nucleosynthesis (BBN) priors and Type Ia supernovae (SNe) measurements from the Pantheon set, in which the impact on the absolute magnitude is also considered. It is found that a state where a phantom crossing of $w_{DE}$ happens is favored by data, and while the $f(T)$ model is equivalent to the $Lambda$CDM one by statistical criteria when CC+SNe+BAO+BBN data is considered, a considerable tension is found when CMB data is added. We also find that the Hubble tension is alleviated in the $f(T)$ model, at the same time that it does not worsen the growth one, indicating a possibility of the scenario as an option to address the current cosmic tensions. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16370v1

Updating constraints on phantom crossing f T gravity by F. B. M. dos Santos. on Wednesday 30 November We establish constraints on $f(T)$ gravity by considering the possibility of a scenario that supports a phantom crossing of the equation of state parameter $w_{DE}$. After determining the viable parameter space of the model, while checking the impact on the background dynamics, we perform an analysis to obtain constraints on cosmological parameters and determine the viability of this scenario. To this end, we use combined data sets from cosmic chronometers (CC), baryonic acoustic oscillations (BAO), redshift space measurements (RSD), cosmic microwave background (CMB) and Big Bang nucleosynthesis (BBN) priors and Type Ia supernovae (SNe) measurements from the Pantheon set, in which the impact on the absolute magnitude is also considered. It is found that a state where a phantom crossing of $w_{DE}$ happens is favored by data, and while the $f(T)$ model is equivalent to the $Lambda$CDM one by statistical criteria when CC+SNe+BAO+BBN data is considered, a considerable tension is found when CMB data is added. We also find that the Hubble tension is alleviated in the $f(T)$ model, at the same time that it does not worsen the growth one, indicating a possibility of the scenario as an option to address the current cosmic tensions. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16370v1

Updating constraints on phantom crossing f T gravity by F. B. M. dos Santos. on Wednesday 30 November We establish constraints on $f(T)$ gravity by considering the possibility of a scenario that supports a phantom crossing of the equation of state parameter $w_{DE}$. After determining the viable parameter space of the model, while checking the impact on the background dynamics, we perform an analysis to obtain constraints on cosmological parameters and determine the viability of this scenario. To this end, we use combined data sets from cosmic chronometers (CC), baryonic acoustic oscillations (BAO), redshift space measurements (RSD), cosmic microwave background (CMB) and Big Bang nucleosynthesis (BBN) priors and Type Ia supernovae (SNe) measurements from the Pantheon set, in which the impact on the absolute magnitude is also considered. It is found that a state where a phantom crossing of $w_{DE}$ happens is favored by data, and while the $f(T)$ model is equivalent to the $Lambda$CDM one by statistical criteria when CC+SNe+BAO+BBN data is considered, a considerable tension is found when CMB data is added. We also find that the Hubble tension is alleviated in the $f(T)$ model, at the same time that it does not worsen the growth one, indicating a possibility of the scenario as an option to address the current cosmic tensions. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16370v1

Using simulated Tianqin gravitational wave data and electromagnetic wave data to study the coincidence problem and Hubble tension problem by JiaWei Zhang et al. on Wednesday 30 November In this paper, we use electromagnetic wave data (H0LiCOW, $H(z)$, SNe) and gravitational wave data (Tianqin) to constrain the interacting dark energy (IDE) model and investigate the Hubble tension problem and coincidences problem. By combining these four kinds of data (Tianqin+H0LiCOW+SNe+$H(z)$), we obtained the parameter values at the confidence interval of $1sigma$: $Omega_m=0.36pm0.18$, $omega_x=-1.29^{+0.61}_{-0.23}$, $xi=3.15^{+0.36}_{-1.1}$, and $H_0=70.04pm0.42$ $kms^{-1}Mpc^{-1}$. According to our results, the best valve of $H_0$ show that the Hubble tension problem can be alleviated to some extent. In addition, the $xi+3omega_x = -0.72^{+2.19}_{-1.19}(1sigma)$ of which the center value indicates the coincidence problem is slightly alleviated. However, the $xi+3omega_x = 0$ is still within the $1sigma$ error range which indicates the $Lambda$CDM model is still the model which is in best agreement with the observational data at present. Finally, we compare the constraint results of electromagnetic wave and gravitational wave on the model parameters and find that the constraint effect of electromagnetic wave data on model parameters is better than that of simulated Tianqin gravitational wave data. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16979v1

Latest data constraint of some parameterized dark energy models by Jing Yang et al. on Wednesday 30 November Using various latest cosmological datasets including Type-Ia supernovae, cosmic microwave background radiation, baryon acoustic oscillations, and estimations of the Hubble parameter, we test some dark energy models with parameterized equations of state and try to distinguish or select observation-preferred models. We obtain the best fitting results of the six models and calculate their values of the Akaike Information Criteria and Bayes Information Criterion. And we can distinguish these dark energy models from each other by using these two information criterions. However, the $Lambda $CDM model remains the best fit model. Furthermore, we perform geometric diagnostics including statefinder and Om diagnostics to understand the geometric behaviour of the dark energy models. We find that the six DE models can be distinguished from each other and from $Lambda$CDM, Chaplygin gas, quintessence models after the statefinder and Om diagnostics were performed. Finally, we consider the growth factor of the dark energy models with comparison to $Lambda $CDM model. Still, we find the models can be distinguished from each other and from $Lambda $CDM model through the growth factor approximation. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15881v1

The CMB cold spot under the lens: ruling out a supervoid interpretation by Stephen Owusu et al. on Wednesday 30 November The Cosmic Microwave Background (CMB) anisotropies are thought to be statistically isotropic and Gaussian. However, several anomalies are observed, including the CMB Cold Spot, an unexpected cold $sim 10^{circ}$ region with $p$-value $lesssim 0.01$ in standard $Lambda$CDM. One of the proposed origins of the Cold Spot is an unusually large void on the line of sight, that would generate a cold region through the combination of integrated Sachs-Wolfe and Rees-Sciama effects. In the past decade extensive searches were conducted in large scale structure surveys, both in optical and infrared, in the same area for $z lesssim 1$ and did find evidence of large voids, but of depth and size able to account for only a fraction of the anomaly. Here we analyze the lensing signal in the Planck CMB data and rule out the hypothesis that the Cold Spot could be due to a large void located anywhere between us and the surface of last scattering. In particular, computing the evidence ratio we find that a model with a large void is disfavored compared to $Lambda$CDM, with odds 1 : 13 (1 : 20) for SMICA (NILC) maps, compared to the original odds 56 : 1 (21 : 1) using temperature data alone. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16139v1

The Hubble Constant Troubled by Dark Matter in Non-Standard Cosmologies by Jailson S. Alcaniz et al. on Tuesday 29 November The Standard Cosmological Model has experienced tremendous success at reproducing observational data by assuming a universe dominated by a cosmological constant and dark matter in a flat geometry. However, several studies, based on local measurements, indicate that the universe is expanding too fast, in disagreement with the Cosmic Microwave Background. Taking into account combined data from CMB, Baryon Acoustic Oscillation, and type Ia Supernovae, we show that if the mechanism behind the production of dark matter particles has at least a small non-thermal origin, one can induce larger values of the Hubble rate $H_0$, within the $Lambda$CDM, to alleviate the trouble with $H_0$. In the presence of non-standard cosmology, however, we can fully reconcile CMB and local measurements and reach $H_0=70-74, {rm km s^{-1} Mpc^{-1}}$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14345v1

The CMB cold spot under the lens: ruling out a supervoid interpretation by Stephen Owusu et al. on Tuesday 29 November The Cosmic Microwave Background (CMB) anisotropies are thought to be statistically isotropic and Gaussian. However, several anomalies are observed, including the CMB Cold Spot, an unexpected cold $sim 10^{circ}$ region with $p$-value $lesssim 0.01$ in standard $Lambda$CDM. One of the proposed origins of the Cold Spot is an unusually large void on the line of sight, that would generate a cold region through the combination of integrated Sachs-Wolfe and Rees-Sciama effects. In the past decade extensive searches were conducted in large scale structure surveys, both in optical and infrared, in the same area for $z lesssim 1$ and did find evidence of large voids, but of depth and size able to account for only a fraction of the anomaly. Here we analyze the lensing signal in the Planck CMB data and rule out the hypothesis that the Cold Spot could be due to a large void located anywhere between us and the surface of last scattering. In particular, computing the evidence ratio we find that a model with a large void is disfavored compared to $Lambda$CDM, with odds 1 : 13 (1 : 20) for SMICA (NILC) maps, compared to the original odds 56 : 1 (21 : 1) using temperature data alone. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16139v1

Latest data constraint of some parameterized dark energy models by Jing Yang et al. on Tuesday 29 November Using various latest cosmological datasets including Type-Ia supernovae, cosmic microwave background radiation, baryon acoustic oscillations, and estimations of the Hubble parameter, we test some dark energy models with parameterized equations of state and try to distinguish or select observation-preferred models. We obtain the best fitting results of the six models and calculate their values of the Akaike Information Criteria and Bayes Information Criterion. And we can distinguish these dark energy models from each other by using these two information criterions. However, the $Lambda $CDM model remains the best fit model. Furthermore, we perform geometric diagnostics including statefinder and Om diagnostics to understand the geometric behaviour of the dark energy models. We find that the six DE models can be distinguished from each other and from $Lambda$CDM, Chaplygin gas, quintessence models after the statefinder and Om diagnostics were performed. Finally, we consider the growth factor of the dark energy models with comparison to $Lambda $CDM model. Still, we find the models can be distinguished from each other and from $Lambda $CDM model through the growth factor approximation. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15881v1

A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Tuesday 29 November Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $zsim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Omega_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Lambda$CDM model with $Omega_M = 0.3$ and $H_0 = 70 , mathrm{km,s^{-1},Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v2

Constraining dark matter decays with cosmic microwave background and weak lensing shear observations by Jozef Bucko et al. on Tuesday 29 November From observations of both low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or, at least, very long-lived. However, the possibility that a small fraction of DM is unstable or that all of DM decays with a half-life time ($tau$) significantly larger than the age of the universe is not ruled out. One-body decaying dark matter (DDM) consists of a minimal extension to the $Lambda$CDM model. It causes a modification of the cosmic growth history as well as a suppression of the small-scale clustering signal, providing interesting consequences regarding the $S_8$-tension, the observed differences of the clustering amplitude between weak lensing (WL) and cosmic microwave background (CMB) observations. In this paper we investigate models where a fraction or all DM decays into radiation, focusing on the long-lived regime i.e. $tau gtrsim H_0^{-1}$ ( $H_0^{-1}$ being the Hubble time). We use WL data from the Kilo-Degree Survey (KiDS) and CMB data from Planck. First, we confirm that this DDM model cannot alleviate the $S_8$-tension. We then show that the most constraining power for DM decays does not come from the nonlinear weak lensing data but from CMB via the integrated Sachs-Wolfe effect. From the CMB data alone, we obtain constraints of $tau geq 288$ Gyr if all the DM is assumed to be unstable, and we show that a maximum fraction of $f=0.07$ is allowed to decay assuming the half-life time to be comparable to (or smaller than) one Hubble time. The constraints from the KiDS-1000 WL data are significantly weaker, being at $tau geq 60$ Gyr and $f

A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Tuesday 29 November Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $zsim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Omega_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Lambda$CDM model with $Omega_M = 0.3$ and $H_0 = 70 , mathrm{km,s^{-1},Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v2

Mirror Dark Sector Solution of the Hubble Tension with Time-varying Fine-structure Constant by John Zhang et al. on Tuesday 29 November We explore a model introduced by Cyr-Racine, Ge, and Knox (arXiv:2107.13000(2)) that resolves the Hubble tension by invoking a ``mirror world" dark sector with energy density a fixed fraction of the ``ordinary" sector of Lambda-CDM. Although it reconciles cosmic microwave background and large-scale structure observations with local measurements of the Hubble constant, the model requires a value of the primordial Helium mass fraction that is discrepant with observations and with the predictions of Big Bang Nucleosynthesis (BBN). We consider a variant of the model with standard Helium mass fraction but with the value of the electromagnetic fine-structure constant slightly different during photon decoupling from its present value. If $alpha$ at that epoch is lower than its current value by $Delta alpha simeq -2times 10^{-5}$, then we can achieve the same Hubble tension resolution as in Cyr-Racine, et al. but with consistent Helium abundance. As an example of such time-evolution, we consider a toy model of an ultra-light scalar field, with mass $m

The Hubble Constant Troubled by Dark Matter in Non-Standard Cosmologies by Jailson S. Alcaniz et al. on Monday 28 November The Standard Cosmological Model has experienced tremendous success at reproducing observational data by assuming a universe dominated by a cosmological constant and dark matter in a flat geometry. However, several studies, based on local measurements, indicate that the universe is expanding too fast, in disagreement with the Cosmic Microwave Background. Taking into account combined data from CMB, Baryon Acoustic Oscillation, and type Ia Supernovae, we show that if the mechanism behind the production of dark matter particles has at least a small non-thermal origin, one can induce larger values of the Hubble rate $H_0$, within the $Lambda$CDM, to alleviate the trouble with $H_0$. In the presence of non-standard cosmology, however, we can fully reconcile CMB and local measurements and reach $H_0=70-74, {rm km s^{-1} Mpc^{-1}}$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14345v1

Constraining dark matter decays with cosmic microwave background and weak lensing shear observations by Jozef Bucko et al. on Monday 28 November From observations of both low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or, at least, very long-lived. However, the possibility that a small fraction of DM is unstable or that all of DM decays with a half-life time ($tau$) significantly larger than the age of the universe is not ruled out. One-body decaying dark matter (DDM) consists of a minimal extension to the $Lambda$CDM model. It causes a modification of the cosmic growth history as well as a suppression of the small-scale clustering signal, providing interesting consequences regarding the $S_8$-tension, the observed differences of the clustering amplitude between weak lensing (WL) and cosmic microwave background (CMB) observations. In this paper we investigate models where a fraction or all DM decays into radiation, focusing on the long-lived regime i.e. $tau gtrsim H_0^{-1}$ ( $H_0^{-1}$ being the Hubble time). We use WL data from the Kilo-Degree Survey (KiDS) and CMB data from Planck. First, we confirm that this DDM model cannot alleviate the $S_8$-tension. We then show that the most constraining power for DM decays does not come from the nonlinear weak lensing data but from CMB via the integrated Sachs-Wolfe effect. From the CMB data alone, we obtain constraints of $tau geq 288$ Gyr if all the DM is assumed to be unstable, and we show that a maximum fraction of $f=0.07$ is allowed to decay assuming the half-life time to be comparable to (or smaller than) one Hubble time. The constraints from the KiDS-1000 WL data are significantly weaker, being at $tau geq 60$ Gyr and $f

Constraints on modified gravity from the BOSS galaxy survey by Lorenzo Piga et al. on Thursday 24 November We develop a pipeline to set new constraints on scale-independent modified gravity, from the galaxy power spectrum in redshift space of BOSS DR12. The latter is modelled using the effective field theory of large-scale structure up to 1-loop order in perturbation theory. We test our pipeline on synthetic and simulated data, to assess systematic biases on the inferred cosmological parameters due to marginalization and theoretical errors, and we apply it to the normal branch of the DGP model with a $Lambda$CDM background. We observe biased posteriors due to the strong degeneracy between the nDGP parameter $Omega_{rm rc}$ and the primordial amplitude of fluctuations $A_s$. Fixing the latter to the Planck central value, we obtain $Omega_{rm rc}lesssim 0.2$ at 95$%$ C.L. We also discuss a procedure to alleviate the prior dependence of this bound. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12523v1

Cosmic Topology I: Limits on Orientable Euclidean Manifolds from Circle Searches by Pip Petersen et al. on Thursday 24 November The Einstein field equations of general relativity constrain the local curvature at every point in spacetime, but say nothing about the global topology of the Universe. Cosmic microwave background anisotropies have proven to be the most powerful probe of non-trivial topology since, within $Lambda$CDM, these anisotropies have well-characterized statistical properties, the signal is principally from a thin spherical shell centered on the observer (the last scattering surface), and space-based observations nearly cover the full sky. The most generic signature of cosmic topology in the microwave background is pairs of circles with matching temperature and polarization patterns. No such circle pairs have been seen above noise in the WMAP or Planck temperature data, implying that the shortest non-contractible loop around the Universe through our location is longer than 98.5% of the comoving diameter of the last scattering surface. We translate this generic constraint into limits on the parameters that characterize manifolds with each of the nine possible non-trivial orientable Euclidean topologies, and provide a code which computes these constraints. In all but the simplest cases, the shortest non-contractible loop in the space can avoid us, and be shorter than the diameter of the last scattering surface by a factor ranging from 2 to at least 6. This result implies that a broader range of manifolds is observationally allowed than widely appreciated.Probing these manifolds will require more subtle statistical signatures than matched circles, such as off-diagonal correlations of harmonic coefficients. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.02603v2

Cosmic Topology I: Limits on Orientable Euclidean Manifolds from Circle Searches by Pip Petersen et al. on Wednesday 23 November The Einstein field equations of general relativity constrain the local curvature at every point in spacetime, but say nothing about the global topology of the Universe. Cosmic microwave background anisotropies have proven to be the most powerful probe of non-trivial topology since, within $Lambda$CDM, these anisotropies have well-characterized statistical properties, the signal is principally from a thin spherical shell centered on the observer (the last scattering surface), and space-based observations nearly cover the full sky. The most generic signature of cosmic topology in the microwave background is pairs of circles with matching temperature and polarization patterns. No such circle pairs have been seen above noise in the WMAP or Planck temperature data, implying that the shortest non-contractible loop around the Universe through our location is longer than 98.5% of the comoving diameter of the last scattering surface. We translate this generic constraint into limits on the parameters that characterize manifolds with each of the nine possible non-trivial orientable Euclidean topologies, and provide a code which computes these constraints. In all but the simplest cases, the shortest non-contractible loop in the space can avoid us, and be shorter than the diameter of the last scattering surface by a factor ranging from 2 to at least 6. This result implies that a broader range of manifolds is observationally allowed than widely appreciated.Probing these manifolds will require more subtle statistical signatures than matched circles, such as off-diagonal correlations of harmonic coefficients. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.02603v2

Constraints on modified gravity from the BOSS galaxy survey by Lorenzo Piga et al. on Wednesday 23 November We develop a pipeline to set new constraints on scale-independent modified gravity, from the galaxy power spectrum in redshift space of BOSS DR12. The latter is modelled using the effective field theory of large-scale structure up to 1-loop order in perturbation theory. We test our pipeline on synthetic and simulated data, to assess systematic biases on the inferred cosmological parameters due to marginalization and theoretical errors, and we apply it to the normal branch of the DGP model with a $Lambda$CDM background. We observe biased posteriors due to the strong degeneracy between the nDGP parameter $Omega_{rm rc}$ and the primordial amplitude of fluctuations $A_s$. Fixing the latter to the Planck central value, we obtain $Omega_{rm rc}lesssim 0.2$ at 95$%$ C.L. We also discuss a procedure to alleviate the prior dependence of this bound. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12523v1

Cosmic Topology I: Limits on Orientable Euclidean Manifolds from Circle Searches by Pip Petersen et al. on Wednesday 23 November The Einstein field equations of general relativity constrain the local curvature at every point in spacetime, but say nothing about the global topology of the Universe. Cosmic microwave background anisotropies have proven to be the most powerful probe of non-trivial topology since, within $Lambda$CDM, these anisotropies have well-characterized statistical properties, the signal is principally from a thin spherical shell centered on the observer (the last scattering surface), and space-based observations nearly cover the full sky. The most generic signature of cosmic topology in the microwave background is pairs of circles with matching temperature and polarization patterns. No such circle pairs have been seen above noise in the WMAP or Planck temperature data, implying that the shortest non-contractible loop around the Universe through our location is longer than 98.5% of the comoving diameter of the last scattering surface. We translate this generic constraint into limits on the parameters that characterize manifolds with each of the nine possible non-trivial orientable Euclidean topologies, and provide a code which computes these constraints. In all but the simplest cases, the shortest non-contractible loop in the space can avoid us, and be shorter than the diameter of the last scattering surface by a factor ranging from 2 to at least 6. This result implies that a broader range of manifolds is observationally allowed than widely appreciated.Probing these manifolds will require more subtle statistical signatures than matched circles, such as off-diagonal correlations of harmonic coefficients. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.02603v2

The galaxy formation origin of the lensing is low problem by Jonas Chaves-Montero et al. on Tuesday 22 November Recent analyses show that $Lambda$CDM-based models optimised to reproduce the clustering of massive galaxies overestimate their gravitational lensing by about 30%, the so-called lensing is low problem. Using a state-of-the-art hydrodynamical simulation, we show that this discrepancy reflects shortcomings in standard galaxy-halo connection models rather than tensions within the $Lambda$CDM paradigm itself. Specifically, this problem results from ignoring a variety of galaxy formation effects, including assembly bias, segregation of satellite galaxies relative to dark matter, and baryonic effects on the matter distribution. All these effects contribute towards overestimating gravitational lensing and, when combined, explain the amplitude and scale dependence of the lensing is low problem. We conclude that simplistic galaxy-halo connection models are inadequate to interpret clustering and lensing simultaneously, and that it is crucial to employ more sophisticated models for the upcoming generation of large-scale surveys. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.01744v2

Exhaustive Symbolic Regression by Deaglan J. Bartlett et al. on Tuesday 22 November Symbolic Regression (SR) algorithms learn analytic expressions which both accurately fit data and, unlike traditional machine-learning approaches, are highly interpretable. Conventional SR suffers from two fundamental issues which we address in this work. First, since the number of possible equations grows exponentially with complexity, typical SR methods search the space stochastically and hence do not necessarily find the best function. In many cases, the target problems of SR are sufficiently simple that a brute-force approach is not only feasible, but desirable. Second, the criteria used to select the equation which optimally balances accuracy with simplicity have been variable and poorly motivated. To address these issues we introduce a new method for SR -- Exhaustive Symbolic Regression (ESR) -- which systematically and efficiently considers all possible equations and is therefore guaranteed to find not only the true optimum but also a complete function ranking. Utilising the minimum description length principle, we introduce a principled method for combining these preferences into a single objective statistic. To illustrate the power of ESR we apply it to a catalogue of cosmic chronometers and the Pantheon+ sample of supernovae to learn the Hubble rate as a function of redshift, finding $sim$40 functions (out of 5.2 million considered) that fit the data more economically than the Friedmann equation. These low-redshift data therefore do not necessarily prefer a $Lambda$CDM expansion history, and traditional SR algorithms that return only the Pareto-front, even if they found this successfully, would not locate $Lambda$CDM. We make our code and full equation sets publicly available. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11461v1

A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Tuesday 22 November Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $zsim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Omega_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Lambda$CDM model with $Omega_M = 0.3$ and $H_0 = 70 , mathrm{km,s^{-1},Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v1

Exhaustive Symbolic Regression by Deaglan J. Bartlett et al. on Monday 21 November Symbolic Regression (SR) algorithms learn analytic expressions which both accurately fit data and, unlike traditional machine-learning approaches, are highly interpretable. Conventional SR suffers from two fundamental issues which we address in this work. First, since the number of possible equations grows exponentially with complexity, typical SR methods search the space stochastically and hence do not necessarily find the best function. In many cases, the target problems of SR are sufficiently simple that a brute-force approach is not only feasible, but desirable. Second, the criteria used to select the equation which optimally balances accuracy with simplicity have been variable and poorly motivated. To address these issues we introduce a new method for SR -- Exhaustive Symbolic Regression (ESR) -- which systematically and efficiently considers all possible equations and is therefore guaranteed to find not only the true optimum but also a complete function ranking. Utilising the minimum description length principle, we introduce a principled method for combining these preferences into a single objective statistic. To illustrate the power of ESR we apply it to a catalogue of cosmic chronometers and the Pantheon+ sample of supernovae to learn the Hubble rate as a function of redshift, finding $sim$40 functions (out of 5.2 million considered) that fit the data more economically than the Friedmann equation. These low-redshift data therefore do not necessarily prefer a $Lambda$CDM expansion history, and traditional SR algorithms that return only the Pareto-front, even if they found this successfully, would not locate $Lambda$CDM. We make our code and full equation sets publicly available. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11461v1

A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Monday 21 November Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $zsim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Omega_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Lambda$CDM model with $Omega_M = 0.3$ and $H_0 = 70 , mathrm{km,s^{-1},Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v1

Machine learning constraints on deviations from general relativity from the large scale structure of the Universe by George Alestas et al. on Monday 21 November We use a particular machine learning approach, called the genetic algorithms (GA), in order to place constraints on deviations from general relativity (GR) via a possible evolution of Newton's constant $muequiv G_mathrm{eff}/G_mathrm{N}$ and of the dark energy anisotropic stress $eta$, both defined to be equal to one in GR. Specifically, we use a plethora of background and linear-order perturbations data, such as type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, redshift space distortions and $E_g$ data. We find that although the GA is affected by the lower quality of the currently available data, especially from the $E_g$ data, the reconstruction of Newton's constant is consistent with a constant value within the errors. On the other hand, the anisotropic stress deviates strongly from unity due to the sparsity and the systematics of the $E_g$ data. Finally, we also create synthetic data based on a next-generation survey and forecast the limits of any possible detection of deviations from GR. In particular, we use two fiducial models: one based on the cosmological constant $Lambda$CDM model and another on a model with an evolving Newton's constant, dubbed $mu$CDM. We find that the GA reconstructions of $mu(z)$ and $eta(z)$ can be constrained to within a few percent of the fiducial models and in the case of the $mu$CDM mocks, they can also provide a strong detection of several $sigma$s, thus demonstrating the utility of the GA reconstruction approach. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.12799v3

The galaxy formation origin of the lensing is low problem by Jonas Chaves-Montero et al. on Monday 21 November Recent analyses show that $Lambda$CDM-based models optimised to reproduce the clustering of massive galaxies overestimate their gravitational lensing by about 30%, the so-called lensing is low problem. Using a state-of-the-art hydrodynamical simulation, we show that this discrepancy reflects shortcomings in standard galaxy-halo connection models rather than tensions within the $Lambda$CDM paradigm itself. Specifically, this problem results from ignoring a variety of galaxy formation effects, including assembly bias, segregation of satellite galaxies relative to dark matter, and baryonic effects on the matter distribution. All these effects contribute towards overestimating gravitational lensing and, when combined, explain the amplitude and scale dependence of the lensing is low problem. We conclude that simplistic galaxy-halo connection models are inadequate to interpret clustering and lensing simultaneously, and that it is crucial to employ more sophisticated models for the upcoming generation of large-scale surveys. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.01744v2

Cosmological Studies from HSC-SSP Tomographic Weak Lensing Peak Abundances by Xiangkun Liu et al. on Monday 17 October We perform weak lensing tomographic peak studies using the first-year shear data from Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey. The effective area used in our analyses after field selection, mask and boundary exclusions is $sim 58 deg^2$. The source galaxies are divided into low- and high-redshift bins with $0.2le z_ple0.85$ and $0.85le z_ple1.5$, respectively. We utilize our halo-based theoretical peak model including the projection effect of large-scale structures to derive cosmological constraints from the observed tomographic high peak abundances with the signal-to-noise ratio in the range of $nu_{rm N}=[3.5,5.5]$. These high peaks are closely associated with the lensing effects of massive clusters of galaxies. Thus the inclusion of their member galaxies in the shear catalog can lead to significant source clustering and dilute their lensing signals. We account for this systematic effect in our theoretical modelling. Additionally, the impacts of baryonic effects, galaxy intrinsic alignments, as well as residual uncertainties in shear and photometric redshift calibrations are also analyzed. Within the flat $Lambda$CDM model, the derived constraint is $S_8=0.758_{-0.076}^{+0.033}$ and $0.768_{-0.057}^{+0.030}$ with the source clustering information measured from the two cluster catalogs, CAMIRA and WZL, respectively. The asymmetric uncertainties are due to the different degeneracy direction of $(Omega_{rm m}, sigma_8)$ from high peak abundances comparing to that from the cosmic shear two-point correlations which give rise approximately the power index $alpha=0.5$. Fitting to our constraints, we obtain $alphaapprox 0.38$ and $Sigma_8=0.772_{-0.032}^{+0.028}$ (CAMIRA) and $0.781_{-0.033}^{+0.028}$ (WZL). In comparison with the results from non-tomographic peak analyses, the $1sigma$ uncertainties on $Sigma_8$ are reduced by a factor of $sim1.3$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.07853v1

BICEP Keck XVII: Line of Sight Distortion Analysis: Estimates of Gravitational Lensing, Anisotropic Cosmic Birefringence, Patchy Reionization, and Systematic Errors by BICEP/Keck Collaboration et al. on Monday 17 October We present estimates of line-of-sight distortion fields derived from the 95 GHz and 150 GHz data taken by BICEP2, BICEP3, and Keck Array up to the 2018 observing season, leading to cosmological constraints and a study of instrumental and astrophysical systematics. Cosmological constraints are derived from three of the distortion fields concerning gravitational lensing from large-scale structure, polarization rotation from magnetic fields or an axion-like field, and the screening effect of patchy reionization. We measure an amplitude of the lensing power spectrum $A_L^{phiphi}=0.95 pm 0.20$. We constrain polarization rotation, expressed as the coupling constant of a Chern-Simons electromagnetic term $g_{agamma} leq 2.6 times 10^{-2}/H_I$, where $H_I$ is the inflationary Hubble parameter, and an amplitude of primordial magnetic fields smoothed over 1 Mpc $B_{1text{Mpc}} leq 6.6 ;text{nG}$ at 95 GHz. We constrain the root mean square of optical-depth fluctuations in a simple "crinkly surface" model of patchy reionization, finding $A^tau

Cosmological Studies from HSC-SSP Tomographic Weak Lensing Peak Abundances by Xiangkun Liu et al. on Monday 17 October We perform weak lensing tomographic peak studies using the first-year shear data from Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey. The effective area used in our analyses after field selection, mask and boundary exclusions is $sim 58 deg^2$. The source galaxies are divided into low- and high-redshift bins with $0.2le z_ple0.85$ and $0.85le z_ple1.5$, respectively. We utilize our halo-based theoretical peak model including the projection effect of large-scale structures to derive cosmological constraints from the observed tomographic high peak abundances with the signal-to-noise ratio in the range of $nu_{rm N}=[3.5,5.5]$. These high peaks are closely associated with the lensing effects of massive clusters of galaxies. Thus the inclusion of their member galaxies in the shear catalog can lead to significant source clustering and dilute their lensing signals. We account for this systematic effect in our theoretical modelling. Additionally, the impacts of baryonic effects, galaxy intrinsic alignments, as well as residual uncertainties in shear and photometric redshift calibrations are also analyzed. Within the flat $Lambda$CDM model, the derived constraint is $S_8=0.758_{-0.076}^{+0.033}$ and $0.768_{-0.057}^{+0.030}$ with the source clustering information measured from the two cluster catalogs, CAMIRA and WZL, respectively. The asymmetric uncertainties are due to the different degeneracy direction of $(Omega_{rm m}, sigma_8)$ from high peak abundances comparing to that from the cosmic shear two-point correlations which give rise approximately the power index $alpha=0.5$. Fitting to our constraints, we obtain $alphaapprox 0.38$ and $Sigma_8=0.772_{-0.032}^{+0.028}$ (CAMIRA) and $0.781_{-0.033}^{+0.028}$ (WZL). In comparison with the results from non-tomographic peak analyses, the $1sigma$ uncertainties on $Sigma_8$ are reduced by a factor of $sim1.3$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.07853v1

Beyond Λ CDM constraints from the full shape clustering measurements from BOSS and eBOSS by Agne Semenaite et al. on Sunday 16 October We analyse the full shape of anisotropic clustering measurements from the extended Baryon Oscillation Spectroscopic survey (eBOSS) quasar sample together with the combined galaxy sample from the Baryon Oscillation Spectroscopic Survey (BOSS). We obtain constraints on the cosmological parameters independent of the Hubble parameter $h$ for the extensions of the $Lambda$CDM models, focusing on cosmologies with free dark energy equation of state parameter $w$. We combine the clustering constraints with those from the latest CMB data from Planck to obtain joint constraints for these cosmologies for $w$ and the additional extension parameters - its time evolution $w_{rm{a}}$, the physical curvature density $omega_{K}$ and the neutrino mass sum $sum m_{nu}$. Our joint constraints are consistent with flat $Lambda$CDM cosmological model within 68% confidence limits. We demonstrate that the Planck data are able to place tight constraints on the clustering amplitude today, $sigma_{12}$, in cosmologies with varying $w$ and present the first constraints for the clustering amplitude for such cosmologies, which is found to be slightly higher than the $Lambda$CDM value. Additionally, we show that when we vary $w$ and allow for non-flat cosmologies and the physical curvature density is used, Planck prefers a curved universe at $4sigma$ significance, which is $sim2sigma$ higher than when using the relative curvature density $Omega_{rm{K}}$. Finally, when $w$ is varied freely, clustering provides only a modest improvement (of 0.021 eV) on the upper limit of $sum m_{nu}$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.07304v1

Prospects of testing late-time cosmology with weak lensing of gravitational waves and galaxy surveys by Anna Balaudo et al. on Thursday 13 October We investigate the synergy of upcoming galaxy surveys and gravitational wave (GW) experiments in constraining late-time cosmology, examining the cross-correlations between the weak lensing of gravitational waves (GW-WL) and the galaxy fields. Without focusing on any specific GW detector configuration, we benchmark the requirements for the high-precision measurement of cosmological parameters by considering several scenarios, varying the number of detected GW events and the uncertainty on the inference of the source luminosity distance and redshift. We focus on $Lambda$CDM and scalar-tensor cosmologies, using the Effective Field Theory formalism as a unifying language. We find that, in some of the explored setups, GW-WL contributes to the galaxy signal by doubling the accuracy on non-$Lambda$CDM parameters, allowing in the most favourable scenarios to reach even percent and sub-percent level bounds. Though the most extreme cases presented here are likely beyond the observational capabilities of currently planned individual GW detectors, we show nonetheless that - provided that enough statistics of events can be accumulated - GW-WL offers the potential to become a cosmological probe complementary to LSS surveys, particularly for those parameters that cannot be constrained by other GW probes such as standard sirens. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.06398v1

Is the Observable Universe Consistent with the Cosmological Principle? by Pavan Kumar Aluri et al. on Thursday 13 October The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is formulated through the Friedmann-Lema^itre-Robertson-Walker (FLRW) cosmologies as the spacetime metric, and culminates in the successful and highly predictive $Lambda$-Cold-Dark-Matter ($Lambda$CDM) model. Yet, tensions have emerged within the $Lambda$CDM model, most notably a statistically significant discrepancy in the value of the Hubble constant, $H_0$. Since the notion of cosmic expansion determined by a single parameter is intimately tied to the CP, implications of the $H_0$ tension may extend beyond $Lambda$CDM to the CP itself. This review surveys current observational hints for deviations from the expectations of the CP, highlighting synergies and disagreements that warrant further study. Setting aside the debate about individual large structures, potential deviations from the CP include variations of cosmological parameters on the sky, discrepancies in the cosmic dipoles, and mysterious alignments in quasar polarizations and galaxy spins. While it is possible that a host of observational systematics are impacting results, it is equally plausible that precision cosmology may have outgrown the FLRW paradigm, an extremely pragmatic but non-fundamental symmetry assumption. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2207.05765v3

Prospects of testing late-time cosmology with weak lensing of gravitational waves and galaxy surveys by Anna Balaudo et al. on Thursday 13 October We investigate the synergy of upcoming galaxy surveys and gravitational wave (GW) experiments in constraining late-time cosmology, examining the cross-correlations between the weak lensing of gravitational waves (GW-WL) and the galaxy fields. Without focusing on any specific GW detector configuration, we benchmark the requirements for the high-precision measurement of cosmological parameters by considering several scenarios, varying the number of detected GW events and the uncertainty on the inference of the source luminosity distance and redshift. We focus on $Lambda$CDM and scalar-tensor cosmologies, using the Effective Field Theory formalism as a unifying language. We find that, in some of the explored setups, GW-WL contributes to the galaxy signal by doubling the accuracy on non-$Lambda$CDM parameters, allowing in the most favourable scenarios to reach even percent and sub-percent level bounds. Though the most extreme cases presented here are likely beyond the observational capabilities of currently planned individual GW detectors, we show nonetheless that - provided that enough statistics of events can be accumulated - GW-WL offers the potential to become a cosmological probe complementary to LSS surveys, particularly for those parameters that cannot be constrained by other GW probes such as standard sirens. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.06398v1

Equality scale-based and sound horizon-based analysis of the Hubble tension by Zhihuan Zhou et al. on Thursday 13 October The Hubble horizon at matter-radiation equality ($k^{-1}_{rm{eq}}$) and the sound horizon at the last scattering surface ($r_s(z_*)$) provides interesting consistency check for the $Lambda$CDM model and its extensions. It is well known that the reduction of $r_s$ can be compensated by the increase of $H_0$, while the same is true for the standard rulers $k_{rm{eq}}$. Adding extra radiational component to the early universe can reduce $k_{rm{eq}}$. The addition of early dark energy (EDE), however, tends to increase $k_{rm{eq}}$. We perform $k_{rm{eq}}$- and $r_s$-based analyses in both the EDE model and the Wess-Zumino Dark Radiation (WZDR) model. In the latter case we find $Delta H_0 = 0.4$ between the $r_s$- and $k_{rm{eq}}$-based datasets, while in the former case we find $Delta H_0 = 1.2$. This result suggests that the dark radiation scenario is more consistent in the fit of the two standard rulers ($k_{rm{eq}}$ and $r_s$). As a forecast analyses, we fit the two models with a mock $k_{rm{eq}}$ prior derived from emph{Planck} best-fit $Lambda$CDM model. Compared with the best-fit $H_0$ in baseline $Lambda$CDM model, we find $Delta H_0 = 1.1$ for WZDR model and $Delta H_0 = - 2.4$ for EDE model. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.06851v1

Šta je tamna materija? Kako je otkrivena? Kako su još krajem 19. veka Lord Kelvin i Poenkare došli do prvih ideja da postoji nedostajuća masa u svemiru koju ne vidimo, a koja nam je neophodna da bismo opisali kretanja zvezda? Šta su rotacione krive galaksija i kako smo na osnovu posmatranja brzina kretanja zvezda u galaksijama zaključili da galaksijama nedostaje masa? Kako je na osnovu upoređivanja vidljive i dinamičke mase Fritz Zwicky došao do sličnog zaključka i kako toj "nedostajućoj masi" dao naziv "tamna materija" 1930-ih godina? Kako je izračunao (i zašto je pogrešio) broj koji nam govori koliko puta više ima tamne materije od vidljive, barionske materije?Šta su nam novo donela radio posmatranja, a posebno posmatranja atomskog vodonika na 21 cm talasne dužine? Kako su Vera Rubin i W. Kent Ford, Jr. otkrili većinu univerzuma i došli do dobrog broja odnosa tamne i vidljive materije?  Na koje još načine možemo da indirektno detektujemo tamnu materiju? Kako smo otkrili njeno postojanje preko gravitacionih sočiva, kako preko anizotropije u kosmičkom mikrotalasnom pozadinskom zračenju i zašto nam anizotropija u CMB-u daje zaključak da je najverovatniji opis Univerzuma onaj koji nudi Lambda-CDM model? Kako MOND ne uspeva da objasni Svemir i zašto je danas paradigma o postojanju tamne materije opšte prihvaćena u nauci? Šta je hladna, a šta topla tamna materija? Kako na čestičnom nivou tragamo za tamnom materijom? Koji su načini indirektne potrage za WIMP-ovima? Kako posmatranjem gama zračenja iz centra Mlečnog puta (ili drugih galaksija) možemo da dođemo do indirektne detekcije tamne materije? Kako tamna materija interaguje međusobno na čestičnom nivou? Koji eksperimenti postoje namenjeni direktnoj detekciji mnogobrojnih kandidata za čestice tamne materije? Sve ovo i još mnogo drugih tema vezanih za tamnu materiju možete čuti u ovoj epizodi Radio Galaksije. Gošća je bila Jovana Petrović, doktorantkinja astrofizike koja se bavi gama zračenjem iz centra Mlečnog puta na Matematičkom fakultetu u Beogradu i game math dizajnom u kompaniji  Playstudios Europe. Support the show