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Ruth Durrer08/06/2026, 12:15
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Chris Clarkson08/06/2026, 14:00
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Pierre Mourier (University of Canterbury)08/06/2026, 14:30
The late Universe features nonlinear deviations from strict homogeneity and isotropy as matter structures develop. These local inhomogeneities may have a non-negligible dynamical impact on the cosmological expansion. Such backreaction effects from the presence of structures also include the growth of spatial curvature over large regions. They can be described in a general-relativistic picture,...
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Maharshi SARMA08/06/2026, 15:30
Precision cosmology suggests that late-time inhomogeneities may no longer be treated as small corrections to the FLRW paradigm. Moreover, recent observational hints of axisymmetric anisotropies in the local expansion rate further motivate analyses beyond linear perturbation theory. Motivated by these issues, the framework called "Covariant Cosmography'' is adopted which describes the...
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Stefano Camera09/06/2026, 10:00
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Jessie Hammond09/06/2026, 10:30
Measuring primordial non-Gaussianity (PNG) is one of the goals of current and future galaxy surveys. Since general relativistic effects are degenerate with any signal measured from PNG, a fully relativistic, non-Newtonian approach is required. In previous studies, integrated line-of-sight effects, such as lensing convergence, Shapiro time delay and integrated Sachs-Wolfe, have largely been...
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Federico Montano (University of Turin)09/06/2026, 11:00
Our well-established gravity model, the theory of general relativity, has been extensively tested in strong-field regimes. However, no observational test has yet confirmed its validity on cosmological scales, where the universe’s dark components are necessary to fit LSS data. The detection of large-scale relativistic effects via galaxy power spectrum measurements would provide such an...
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Henry Grasshorn Gebhardt09/06/2026, 12:00
SPHEREx is in the process of surveying the full sky every six months in 102 spectro-photometric bands from 0.75 to 5 micrometers. This will allow SPHEREx to measure redshifts for about 500 million galaxies out to about z < 4. The unprecedentedly large volume is forecast to allow measurement of local non-Gaussianity with statistical uncertainty below order unity. For the main part of the talk I...
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William Luke Matthewson (Korea Astronomy and Space science Institute (KASI))09/06/2026, 12:30
The angular power spectrum of redshift fluctuations is a novel observable that involves a specific kind of weighting of the galaxy number counts, meant to recover complementary information, using the redshift distribution along the line of sight. This has been shown to be generally effective in improving constraining power when combined with the conventional angular power spectrum, and was...
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Bartolomeo Bottazzi Baldi (University of Padua)09/06/2026, 14:30
Current and forthcoming galaxy surveys will map the observable Universe with unprecedented depth, sky coverage, and precision. These maps are affected by relativistic redshift-space distortions (RSDs), which become increasingly relevant on ultra-large scales. Accurate modelling of these relativistic RSDs is essential to avoid systematic biases in key cosmological measurements, such as...
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5. Hard Mode: The Galaxy Angular Bispectrum with Relativistic Effects and Primordial Non-GaussianityThomas Montandon (Laboratoire Univers et Particules de Montpellier)09/06/2026, 15:00
The bispectrum of galaxy number counts is a key probe of large-scale structure, offering sensitivity to nonlinear gravitational evolution, galaxy bias, and primordial non-Gaussianity (PNG). In this talk, I present the first full-sky computation of the angular bispectrum in second-order perturbation theory without the Limber approximation, formulated for finite redshift bins via tomographic...
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Jade Piat09/06/2026, 15:30
Understanding the accelerated expansion of the Universe remains one of the key challenges in cosmology. Leading explanations which do not rely on a cosmological constant are dark energy and modifications of General Relativity, both of which require robust tests on large scales. The Dark Energy Spectroscopic Instrument (DESI) provides unprecedented precision in measuring galaxy clustering from...
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Marie-Noëlle Célérier (Observatoire de Paris-PSL)10/06/2026, 10:00
In the current era of precision cosmology, it is well-known that the present standard $\Lambda$CDM model, despite its successes, is an insufficient average of our actual Universe. Given the recorded tensions between theory and observations, it appears that a more precise representation of the local universe is mandatory. Since General Relativity (GR) is the best theory currently available to...
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Jessica Santiago10/06/2026, 10:30
The Cosmological Principle predicts that, on sufficiently large scales, cosmic expansion should appear statistically isotropic to all observers. Testing the limitations of this prediction in the local Universe is, therefore, a first step into properly considering the impacts of local large-scale anisotropies in data analysis and interpretation. In this work, we use the Cosmicflows-4 distance...
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Yan-Chuan Cai (University of Edinburgh)10/06/2026, 11:00
I will present the detection of Gpc-scale dipoles in gravitational potentials in the large-scale structure of the Universe. Large-scale transverse peculiar velocities are used as signposts and correlated with CMB temperature maps and gravitational lensing maps, revealing dipoles on angular scales of tens of degrees. I will also present constraints on general relativity derived from these new...
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Julien Larena10/06/2026, 12:00
Massive galaxies, acting as gravitational lenses, can form greatly distorted images of background galaxies in so called strong lensing events. When background galaxy and lens are almost aligned along the line of sight, the image take the shape of an Einstein ring whose shape encodes basic properties of the lens.
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However, since lenses are not isolated objects in an otherwise perfectly... -
Benedetta Rosatello (University of Geneva)10/06/2026, 12:30
A direct, model-independent probe of the validity of theories beyond General Relativity and the concordance LCDM model is provided by the Weyl potential, the sum of the temporal and spatial distortions of the spacetime geometry. Its measurement, obtained by combining galaxy clustering and galaxy-galaxy lensing data from the Dark Energy Survey (DES-Y3), is in tension with the LCDM prediction at...
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Jose Fonseca11/06/2026, 10:00
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ZHENG ZHANG11/06/2026, 10:30
In conventional weak-lensing analyses, the lensing projection is treated
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as a direct statistical remapping: the convergence power spectrum inherits from the matter power spectrum, the convergence bispectrum from the matter bispectrum, and so on.
In this work we develop a first-principles theoretical framework that goes beyond this approximate projection scheme. By formulating the... -
James Adam (University of the Western Cape)11/06/2026, 11:00
The Cosmological Principle, which assumes both homogeneity and isotropy on large scales, is a cornerstone of the standard model of cosmology and shapes how we view the Universe and our place within it. It is imperative, then, to devise multiple observational tests which can identify and quantify possible violations of this foundational principle. One possible method of probing large-scale...
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Pritha Paul11/06/2026, 12:00
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Marco Bruni (University of Portsmouth)11/06/2026, 12:30
In this talk I will give an overview of work on non-perturbative nonlinear structure formation in ΛCDM in the context of General Relativity (GR). Using a "post-Friedmann" approximation, I will show how, at leading order, the gravito-magnetic vector potential (AKA frame-dragging potential) is generated by the momentum density on nonlinear scales, and can be extracted from ILLUSTRIS ...
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Pierre Béchaz (University of Pisa & INFN, Pisa)11/06/2026, 14:30
With high-precision data about to be delivered by large-scale surveys, the development of higher-order perturbative descriptions of cosmological observables is becoming increasingly important. Among the others, the redshift drift, being sensitive to local variations in the Hubble factor, paves the way for direct tests of the cosmic acceleration history. More in general, it enables real-time...
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Laurent MAGRI--STELLA (Laboratoire d'Annecy de Physique des Particules)12/06/2026, 10:00
Are the standard approximations used in gravitational lensing still adequate in the era of precision cosmology? If not, how can we move beyond them?
As cosmological tensions sharpen, a new generation of surveys such as Euclid and LSST is set to deliver an unprecedented volume of data, with billions of galaxies analyzed through increasingly sophisticated pipelines, including machine-learning...
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Fabien Castillo (LUX, Observatoire de Paris)12/06/2026, 10:30
The new generation of galaxy surveys will reach an unprecedented precision, allowing to test cosmology and gravity theories from the relativistic effects on the clustering of matter in the universe. In particular, the magnification bias, the change of observed galaxy density caused by lensing magnification, can be used as a cosmological probe. In this work, we investigate the impact of the...
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Joaquin Armijo12/06/2026, 11:00
We study environment-dependent clustering using the marked correlation function applied to Hu-Sawicki $f(R)$ modified gravity simulations. This gravity theory enriches the structure formation by enhancing gravity in a scale-dependent form. By employing a multi-scale cosmic structure finder algorithm, we define the cosmic environments divided in: nodes, filaments, walls and voids. We find a...
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Sankalan Bhattacharyya12/06/2026, 12:00
Current and anticipated large-scale structure surveys are mapping the Lyman-alpha forest on growing cosmological scales, enabling measurements of the Baryon Acoustic Oscillation (BAO) peak and motivating a careful accounting of theoretical systematics at sub-percent precision. Among these systematics, the inhomogeneous Ultra-Violet Background (UVB) has received growing attention, yet its...
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21. Hermes - Towards an Ultimate High-Performance Algorithm for Cosmic Statistics of Large Data SetsTengpeng Xu (Sun Yat-sen University)12/06/2026, 12:30
Driven by the need for fast and efficient algorithms in cosmic statistics to handle the massive data volumes from ongoing and forthcoming galaxy surveys, we present the first public release of Hermes (HypER-speed MultiREsolution cosmic Statistics) — an open-source, parallelized, and GPU-accelerated Python package. At its core, Hermes implements the MRA-CS (MultiResolution Analysis for Cosmic...
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