General relativity has been tested in the solar system and with other astrophysical observations and passed all tests with flying colours. However, these were essentially tests of the vacuum Einstein equations. Cosmology is different. Not only do we test GR on much larger scales, but it is also a very essential non-vacuum solution of the theory.
Observing LSS we cannot only measure the...
In this talk I will review recent work on understanding the importance of GR effects in the correlation function or power spectrum of spectroscopic data, with an emphasis on Infra-Red cancellations and their physical meaning. I will then discuss how any quantitative accurate statement about GR effects cannot be made without taking into account a large number of observational effects that...
In the next few years, the upcoming large-scale structure surveys such as DESI, Euclid, and particularly SPHEREx, are expected to significantly enhance sensitivity in detecting the signature of primordial local non-Gaussianities (PNG), through the scale-dependent bias on the large scale limit of the galaxy power spectrum.
However, on such large scales, this PNG could be confused with general...
SPHEREx is a full-sky galaxy survey that will launch in early 2025. It will detect ~500 Million galaxies over a redshift range 0 to ~4 with spectro-photometric redshifts. SPHEREx is designed to measure the scale-dependent galaxy bias due to primordial non-Gaussianity on large scales. However, general relativistic effects show a similar scale dependence in the power spectrum and are projected...
The distortions in the galaxy number count introduced by perturbations in the spacetime can be measured by the Fourier power spectrum and bispectrum. The study of these spectra often uses the distant observer approximation where the line-of-sight (LOS) vectors are always parallel. But, it has been shown that going beyond this plane-parallel assumption introduces wide-angle corrections to the...
Future galaxy surveys will observe tens of million of sources over large fraction of the sky and various cosmic epochs. Currently, statistical analyses of galaxy distributions and their clustering are performed employing simplifying assumptions such as the flat sky and plane parallel ones. In order to obtain not only precise, but accurate analyses for future datasets, a more precise formalism...
The three-dimensional galaxy power spectrum is a powerful probe of primordial non-Gaussianity and additional general relativistic effects, which become important on large scales. At the same time, wide-angle (WA) effects due to differing lines-of-sight (LOS) on the curved sky also become important with large angular separation. In this talk, we present a new way to non-perturbatively model WA...
As our maps of Large Scale Structure increase in scale and precision and larger volumes are probed, it is crucial to properly model the observable quantities to construct robust predictions and maximize the information extracted by these new surveys. We present a full methodology for analyzing galaxy clustering on the lightcone with the 2-point correlation in the Spherical Fourier-Bessel (SFB)...
Forthcoming weak lensing and galaxy clustering surveys, such as Euclid and LSST, offer unprecedented statistical precision. If new physics is to be discovered from these data sets, standard analysis methods that have previously sufficed must be carefully scrutinised. I will present recent calculations of several subtle biases that arise from neglecting non-linearity in the underlying density...
In this talk I will present a new methodology to measure the Weyl potential, which is the sum of the spatial and temporal distortions of the Universe's geometry, in a model independent way. I will then present how combining galaxy clustering and galaxy-galaxy lensing data from the Dark Energy Survey Year 3 measurements we can provide the first direct measurement of the evolution of the Weyl...
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. However, since lenses are not isolated objects in an otherwise perfectly...
New surveys of the large-scale structure will offer the chance to probe up to the Hubble scale to with percentage level precision. Therefore, in order to accurately infer information from these scales, we must consider percentage level corrections to our theoretical corrections that affect our observables. These include contributions from Doppler-type relativistic projection effects as well as...
Upcoming galaxy surveys aim to map the universe with unprecedented precision, depth and sky coverage. The galaxy bispectrum is a prime source of information as it allows us to probe primordial non-Gaussianity (PNG), a key factor in differentiating various models of inflation. On the scales where local PNG is strongest, Doppler and other relativistic effects become important and need to be...
Upcoming surveys of cosmic structures will probe scales ranging from the nonlinear regime to scales close to the cosmological horizon. This opens up the possibility of probing the ΛCDM model, as well as early universe scenarios with non-Gaussianity. Modeling the galaxy bispectrum is challenging, as it involves general relativity, radiation, and large nonlinearities. In this talk, I will...
There are several effects that distort the clustering of galaxies, the largest of which being the well-known redshift-space distortion. In this talk I will discuss the more subtle effect of gravitational redshift. The impact of this non-kinematic effect in the auto-correlations is suppressed relative to RSD and is best probed in the odd multipoles of the cross-correlation function between...
We investigate the effects imprinted in a cross-correlation function between galaxy positions and intrinsic galaxy shapes (GI correlation). We present an analytical model of the GI correlation function, from which we find that the relativistic effects induce non-vanishing odd multipole anisotropies.We then estimate the signal-to-noise ratio and show that the GI dipole induced by the...
We study the simplest non-perturbative statistics -- the one-point probability distribution function (PDF) for the averaged matter density inside spherical cells. The leading part to the PDF is defined by spherical collapse dynamics, whereas the next-to-leading part comes from the integration over fluctuations around the saddle-point solution. The latter calculation receives sizable...
In this talk I will discuss several new probes and considerations for large-scale structure measurements, which go beyond the most common 2x3pt shear and galaxy clustering measurements for cosmology. Firstly, I will discuss newly discovered cross-correlations between gravitational shear and flexion, including their surprising anticommutative properties. Secondly, I will discuss our latest...
Going beyond linear perturbation theory in cosmology brings several novel phenomena, among which the unavoidable mixing of scalar and tensor perturbation modes. While some of such effects - such as the generation of the so-called Scalar-Induced-Gravitational-Wave background - are nowadays quite popular and largerly analyzed, there are other effects which are less known and deserve...
Is it possible to construct a detailed model of local spacetime in a completely model-independent and non-perturbative manner? Specifically, this would involve developing an observationally viable and physically meaningful method for identifying and classifying angular distortions present in the distance-redshift relation, without relying on the cosmological principle or the notion of peculiar...
We present a comparative analysis of the fluctuation field in the expansion rate of the local universe ($z<0.1$) using galaxy samples (Cosmicflows-4) and supernova samples (Pantheon+). Employing spherical harmonic decomposition, we examine the anisotropy patterns across different redshift shells and observe a significant coherence in these patterns extending to the deepest regions...
Peculiar velocities surveys are going to play a key role in testing our knowledge about the nearby universe and our cosmological assumptions. In this talk I will review some recent fundings and analysis that have been developped concerning these novel observables
To date, the most precise measurement of the observer's peculiar velocity comes from the dipole in the Cosmic Microwave Background. This velocity also generates a dipole in the source number counts. However its amplitude is unfortunately also sensitive to specific properties of the sources, that are difficult to determine precisely. Current studies give dipoles well aligned with the CMB...
Recent measurements of the 4-point correlation function in large-scale galaxy surveys have found apparent evidence of parity violation in the distribution of galaxies. This cannot happen via dynamical gravitational effects in general relativity. If such a violation arose from physics in the early Universe it could indicate important new physics beyond the standard model, and would be at odds...
One of the cornerstones of the standard model of cosmology is the assumption that, on large scales, the Universe is homogeneous and isotropic. Some dark energy and modified gravity models, however, naturally lead to large-scale anisotropies. Thus, it is of great importance to test this broad assumption. One possible method of probing these anisotropies involves the use of weak gravitational...
In this talk, I will discuss the possibility of inferring properties of our Universe using a suitably trained neural network classifier. These properties can range from the nature of the gravitational interaction, to the energy content, to the presence of relativistic phenomena at cosmological scales. I will also discuss the difficulties faced by this approach, particularly in error modeling,...
In my presentation I will start with an overview of the Euclid satellite, discuss its current status and show some recent early results. I will then give a brief outlook of the expected science results in the coming years.
Gravitational redshift and Doppler effects give rise to an antisymmetric component of the galaxy correlation function when cross-correlating two galaxy populations or different tracers. Relativistic effects can be isolated from density and redshift space distortions (RSDs) clustering signals by splitting the galaxy population into two catalogs and using adapted estimators, such as the dipole...
A homogeneous spherical cloud of pressureless matter ( M ) at rest will eventually collapse into a black hole characterized by its gravitational radius ( R_s = 2GM ). This forms what we term a Black Hole Universe (BHU). The BHU necessitates a boundary term to ensure that nothing can escape ( R_s ). This boundary term modifies Einstein’s field equations by adding a component that behaves...
The description of gravity, i.e. the theory of general relativity, plays a crucial role in our understanding of the universe. However, confirmations of the validity of this theory on cosmological scales have hitherto eluded us. In this context, the detection of relativistic Doppler via galaxy power spectrum measurements could further confirm the validity of general relativity at scales very...
Future surveys will measure galaxy clustering on unexplored regimes and with better than ever precision.
In my talk I will discuss some investigations on how this precision will be wasted if not matched by a comparable level of accuracy.
I will present the recent developement of a formalism for including radial modes information and new observables based on it.
Furthermore, I will show...
Large scale structure correlators will be one of the most important probes of fundamental physics in the years to come. The results of redshift surveys which are used to measure these correlators sort their results into redshift bins for convenient analysis. In this short talk, we will discuss the implementation of corrections to account for differences in redshift between observables in the...
Upcoming galaxy survey data will reach unprecedented precision, which calls for a matching level of accuracy in the theoretical modeling of our observables. Recently, a novel formalism has been developed to account for unequal-time corrections in the two-point correlations, when the two objects being correlated are not at the same redshift. In this talk, for the first time, I include general...
The angular power spectrum is a key observable for upcoming high-precision cosmological surveys. However, modelling them typically involves the numerical evaluation of highly oscillatory 3-dimensional integrals that are computationally expensive using brute-force methods. In recent years, there has been increased interest in numerical methods that go beyond the well-known Limber approximation...
Galaxy clustering provides a powerful way to probe cosmology. This requires understanding of the background mean density of galaxy samples, which is estimated from the survey itself by averaging the observed galaxy number density over the angular position. The angle average includes not only the background mean density, but also the monopole fluctuation at each redshift. Here for the first...
A new avenue was recently developed for analyzing large-scale structure data with a model-independent approach, in which the linear power spectrum shape is parametrized with a large number of freely varying wavebands rather than by assuming specific cosmological models. Here we show, using a Fisher matrix approach, that the precision of this method for the case of the one-loop power spectrum...
Large-Scale Structure cosmology has made tremendous progress in the last few years, and is now able to place constraints on cosmological parameters with a precision rivalling that achieved by CMB experiments. In this process, the concordance Lambda CDM model has been shown to provide a very reasonable description of the evolution of the Universe's structure and expansion at late times....
The distribution of galaxies provides an ideal laboratory to test deviations from General Relativity. In particular, constraints on gravity modifications are commonly obtained by measuring the growth of cosmic structures through redshift-space distortions. However, such constraints rely on the validity of the weak equivalence principle, which has never been tested for the dark matter...
In this study, we examine the novel effects of peculiar velocities on color selection in galaxy surveys, with a focus on their implications for the analysis of large-scale structure. Our work quantifies the interplay between the peculiar velocities of Emission Line Galaxies (ELGs) and the color filters employed in the DESI survey. We show that these velocities can shift spectral emission...
The novel observable \hat{J}, capturing the evolution of the combined gravitational potential Ψ + Φ, provides a powerful and model-independent test of gravity. As I will demonstrate in this talk, its full capacity comes into play when being combined with further cosmological observables. Together with measurements of the growth of structure \hat{f}, accessible via redshift-space distortions,...
Local effects in a clumpy Universe affect photon paths and give rise to non-Gaussian features in the large-scale structure. We evaluate the higher-order moments for the distribution of the luminosity distance by adopting the averaging formalism on the past light cone. We compute the skewness in the Hubble-Lemaître diagram at the leading order in the cosmological perturbative expansion of the...
Third generation gravitational waves (GWs) observatories such as Einstein Telescope and Cosmic Explorer will yield an abundance of extra-galactic transient objects. Cross-correlations using GW merger events offer novel and powerful insights into the large-scale distribution of matter in the universe. These sources carry information on their luminosity distance, but remain uninformative about...
First-order gravitational lensing is a pure gradient, and hence only gives image magnification and shear. But post-Born corrections give rise to an additional small image rotation. I discuss the impact of this rotation on galaxies and the CMB temperature and polarization, and explain the challenges in trying to measure it. The rotation is somewhat enhanced for CMB lensing due to the large...
Lensing rotation (or curl lensing or shear B-modes) vanish at leading order in a concordance cosmology. However, it can be produced from sequential lensing events and is therefore a unique post-Born lensing observable. This rotation forms bispectra with other large-scale structure tracers, which can be leveraged to optimally probe the rotation as a cross-spectrum signal. I describe this...
The accelerated expansion of the Universe is canonically attributed to the Dark Energy (DE), encapsulated in the Lambda factor in the Einstein field equations of gravity, but its nature is still not understood. While observations supply strong evidence in favor of the standard model of cosmology Lambda-CDM, a plethora of different modified gravity models (MG) can still arise and describe...
In the evolving landscape of modern precision cosmology, the continuous progress of ongoing and upcoming surveys has provided us an unprecedented level of statistical power. Throughout my doctoral journey, I have mostly explored the Cosmic Microwave Background (CMB) at small angular scales, seeking to constrain cosmological parameters. My research has been dedicated to the development of...
In this talk, I would like to highlight some key results from our RayGal studies of the impact of general relativistic effects on the apparent distribution of large-scale structures down to non-linear scales. We have investigated the dipole of the halo-halo cross-correlation from the 150 Mpc/h scale to the 5 Mpc/h scale. At large scales, we recover the linear expectation while at scales...
The current concordance model of cosmology has been extremely successful in constraining the global properties of the universe. However, it is based on the assumption of statistical homogeneity and isotropy, and we are thus lead to test this global geometry. In practice, it is sufficient to constrain mild anisotropies, and I will show how anisotropy can be considered as a special...
Real-time measurements are becoming feasible in cosmology, where the next generation of telescopes such as the Square Kilometer Array and the Extremely Large Telescope will detect the temporal change of redshifts of individual sources with a precision that will allow a direct detection of the cosmic expansion rate. These detections of cosmic drifts of redshifts are likely to become...
The cosmic web is the largest geometric structure in our universe, consisting of an intricate network of empty voids bounded by thin walls, elongated filaments, and dense clusters. Given the array of upcoming cosmological redshift surveys, new analytic tools are needed to study the formation of the various structures, quantify the geometry and topology, and isolate the elements of the cosmic...
Despite more than a decade of effort, we still need to understand why our inference of cosmological parameters from early and late time Universe probes, most notably the value of the Hubble constant, differ. One of the reasons might be that the Universe, despite being homogeneous and isotropic on very large scales, is highly inhomogeneous at smaller ones, where we live and perform our...
Light propagation in cosmology is usually studied in the geometrical optics approximation which requires the spacetime curvature to be much smaller than the light wavenumber. However, for non-fuzzy particle dark matter the curvature is concentrated in widely separated spikes at particle location. We consider a post-geometrical optics approximation that includes curvature and solve the...
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the SARAO Square Kilometer Array (SKA) site in South Africa. Through 21cm Intensity Mapping, HIRAX will provide a cosmological survey of the distribution of the large-scale structure over the redshift range of $ 0.775...
This study breaks new ground by reconstructing how dark energy behaves over time, and we do it without tying ourselves to any specific cosmological model or parametrization. Instead, we rely on actual data to guide our analysis, making this the first study to combine the cosmological background and the growth observations to understand dark energy. We use information about the Hubble parameter...
