367 research outputs found
Numerical complexity of the joint nulled weak-lensing probability distribution function
No full textBarthelemy A, Bernardeau F, Codis S, Uhlemann C. Numerical complexity of the joint nulled weak-lensing probability distribution function. Physical Review D. 2022;105(4): 043537.In the context of tomographic cosmic shear surveys, there exists a nulling transformation of weak lensing observations (also called BNT transform) that allows us to simplify the correlation structure of tomographic cosmic shear observations, as well as to build observables that depend only on a localized range of redshifts and thus independent from the low-redshift/small-scale modes. This procedure renders possible accurate, and from-first-principles, predictions of the convergence and aperture mass one-point distributions (PDF). We here explore other consequences of this transformation on the (reduced) numerical complexity of the estimation of the joint PDF between nulled bins and demonstrate how to use these results to make theoretical prediction
BEYOND THE POWER SPECTRUM WITH LARGE DEVIATION THEORY
No full textInternational audienceA large-deviation principle is used to model the time-evolution of the large-scale structure of the Universe. This approach allows for analytical predictions in the mildly non-linear regime, beyond what is commonly achievable via other statistics such as correlation functions. The idea is to measure the mean cosmic densities within concentric spheres and study their joint statistics.The spherical symmetry then leads to surprisingly accurate predictions where standard calculations of perturbation theory usually break down. Results for the one-point statistics of the cosmic density field are shown and implications for future large galaxy surveys are discussed
Theoretical modelling of non-linear effects on the statistics of weak gravitational lensing fields
No full textL’astigmatisme cosmique est une conséquence directe de la relativité générale d’Einstein (ou de ses extensions) et décrit comment la présence de matière – au sens large du tenseur énergie-impulsion – déforme les trajectoires des rayons lumineux se propageant autrement en ligne droite.Cet effet, faible lorsqu’appliqué aux très grandes structures de l’Univers, se traduit par de très légères déformations des formes des galaxies d’arrière plan qui sont ainsi vues comme des variables aléatoires très corrélées puisque pour partie résultantes des corrélations existant dans les structures du champ de matière lui-même. L’étude de ces corrélations du champ des formes des galaxies est ainsi une sonde de la structuration du champ de matière totale, structuration qui contient en elle de fortes signatures, entre autres, du modèle cosmologique et de la théorie de la gravitation s’approchant au mieux des lois naturelles à l’oeuvre dans notre Univers. Malheureusement, les équations que nous utilisons pour décrire la formation des grandes structures de notre Univers n’ont pour le moment pas de solutions analytiques ce qui complique notre étude. Ainsi, en complément des outils numériques utilisés par une partie de la communauté scientifique, ce travail de thèse s’attache à proposer une modélisation théorique de la statistique à un point de certaines composantes du champs de déformation des galaxies: la convergence et la masse d’ouverture, toutes deux rattachées à la déformation isotrope des galaxies d’arrière plan. En utilisant une approche inspirée de la théorie mathématique des grandes déviations et une ré-organisation de l’information connue sous le nom de transformation de BNT, sont construites et proposées de nouvelles observables riches en information cosmologique et accessibles par une modélisation purement théorique partant de premiers-principes communément admis dans la communauté scientifique en Astrophysique et Cosmologie.Gravitational lensing is a direct consequence of Einstein’s theory of general relativity and its extensions. It describes how the presence of matter – or more generally of a stress–energy tensor– changes how light propagates through the Universe. When applying this effect to the very large-scale structures of our Universe, we find that the images of distant galaxies that we observe are not exactly accurate but instead are slightly distorted because of this effect. This results in galaxy shapes becoming correlated since now partly resulting from the correlation of the matter field itself which is responsible for the observed deformation. The study of these correlations is thus a direct probe of the cosmological model and the theory of gravitation that mimic best the natural laws at play in ourUniverse. Unfortunately, the equations that we use to describe the formation of large structures in our universe do not admit any analytical solutions which lead part of the astrophysics community to rely on numerical simulations to gain information on how our models influence the formation of structures.My thesis work is complementary to these approaches as it proposes a pure theoretical modelling of certain components of the one-point statistics of the deformation field, namely the convergence and the aperture mass that are both related to the isotropic deformation of the image of background sources.Using an approach inspired by the mathematical theory of large deviations and a re-organisation of the contributing matter-structures along the lines of sight known as BNT transform, I build and propose an accurate theoretical model for cosmological-information-rich observables based on first physical principles commonly admitted in the community
De la cosmologie à la formation des galaxies : que nous apprennent les grandes structures de l'Univers ?
No full textThis thesis by publication is devoted to the theoretical understanding of the large-scale structure of the Universe and its role in the context of cosmology and galaxy formation. The birth and evolution of galaxies occur within the large cosmic highways drawn by the cosmic web and the natural question which arises is whether galaxies retain a memory of the large-scale cosmic flows from which they emerge. To address this key question, we will first show that in cosmological simulations, the spin of galaxies and the direction of their host filament are correlated in a mass-dependent way. This signal will be shown to be qualitatively understood in the context of hierarchical structure formation. An analytic model which explicitly takes into account the anisotropy of the cosmic web will complement this qualitative understanding by reproducing the measured correlations. Those ideas are important to understand the evolution of galaxy morphology but also to understand the intrinsic alignments of galaxies that contaminate cosmological probes like cosmic shear experiments. We will in particular measure this contamination directly from a state-of-the-art hydrodynamical simulation. In a second part, we will address the question of how to efficiently use large-scale structure data to probe the cosmological model describing our Universe by measuring its topology and geometry and using perturbation theory in the weakly and even mildly non-linear regime. The major contribution of this work is to analytically study the effect of redshift space distortions and non-linear collapse of structures on the topology, geometry and statistics of the cosmic density field.Dans cette thèse sur articles, nous nous intéressons aux grandes structures de l’Univers et à leur rôle fondamental pour la cosmologie et la formation des galaxies. Les galaxies naissent et grandissent au sein des filaments de la toile cosmique soulevant la question de l’impact de ces filaments sur les propriétés galactiques telles que la morphologie. Pour étudier cette question fondamentale, nous allons dans un premier temps montrer que dans les simulations numériques de l’Univers, le spin des galaxies est fortement lié à la direction de leur filament hôte avec un comportement qui dépend de leur masse. Ces corrélations spin-filament seront expliquées qualitativement dans le contexte de la formation hiérarchique des structures cosmologiques. Un modèle analytique tenant compte de l’anisotropie de la toile cosmique complètera ce tableau en reproduisant les corrélations observées. Ces idées sont importantes pour comprendre la morphologie des galaxies mais aussi les alignements intrinsèques qui peuvent certaines sondes cosmologiques basées sur la mesure de l’astigmatisme cosmique. Nous allons en particulier mesurer cette contamination dans une simulation hydrodynamique. Dans la seconde partie de ce manuscrit, nous nous poserons la question de comment extraire efficacement de l’information de la toile cosmique en mesurant sa topologie et sa géométrie et en utilisant la théorie perturbative dans un régime quasi-linéaire, la pierre angulaire de ce travail reposant sur l’étude analytique de l’impact de l’effondrement non-linéaire des structures et des distorsions en espace des redshifts sur la statistique du champ de densité cosmique
From cosmology to galaxy formation : what can we learn from the large-scale structure of the Universe ?
No full textDans cette thèse sur articles, nous nous intéressons aux grandes structures de l’Univers et à leur rôle fondamental pour la cosmologie et la formation des galaxies. Les galaxies naissent et grandissent au sein des filaments de la toile cosmique soulevant la question de l’impact de ces filaments sur les propriétés galactiques telles que la morphologie. Pour étudier cette question fondamentale, nous allons dans un premier temps montrer que dans les simulations numériques de l’Univers, le spin des galaxies est fortement lié à la direction de leur filament hôte avec un comportement qui dépend de leur masse. Ces corrélations spin-filament seront expliquées qualitativement dans le contexte de la formation hiérarchique des structures cosmologiques. Un modèle analytique tenant compte de l’anisotropie de la toile cosmique complètera ce tableau en reproduisant les corrélations observées. Ces idées sont importantes pour comprendre la morphologie des galaxies mais aussi les alignements intrinsèques qui peuvent certaines sondes cosmologiques basées sur la mesure de l’astigmatisme cosmique. Nous allons en particulier mesurer cette contamination dans une simulation hydrodynamique. Dans la seconde partie de ce manuscrit, nous nous poserons la question de comment extraire efficacement de l’information de la toile cosmique en mesurant sa topologie et sa géométrie et en utilisant la théorie perturbative dans un régime quasi-linéaire, la pierre angulaire de ce travail reposant sur l’étude analytique de l’impact de l’effondrement non-linéaire des structures et des distorsions en espace des redshifts sur la statistique du champ de densité cosmique.This thesis by publication is devoted to the theoretical understanding of the large-scale structure of the Universe and its role in the context of cosmology and galaxy formation. The birth and evolution of galaxies occur within the large cosmic highways drawn by the cosmic web and the natural question which arises is whether galaxies retain a memory of the large-scale cosmic flows from which they emerge. To address this key question, we will first show that in cosmological simulations, the spin of galaxies and the direction of their host filament are correlated in a mass-dependent way. This signal will be shown to be qualitatively understood in the context of hierarchical structure formation. An analytic model which explicitly takes into account the anisotropy of the cosmic web will complement this qualitative understanding by reproducing the measured correlations. Those ideas are important to understand the evolution of galaxy morphology but also to understand the intrinsic alignments of galaxies that contaminate cosmological probes like cosmic shear experiments. We will in particular measure this contamination directly from a state-of-the-art hydrodynamical simulation. In a second part, we will address the question of how to efficiently use large-scale structure data to probe the cosmological model describing our Universe by measuring its topology and geometry and using perturbation theory in the weakly and even mildly non-linear regime. The major contribution of this work is to analytically study the effect of redshift space distortions and non-linear collapse of structures on the topology, geometry and statistics of the cosmic density field
Large-separation expansion of peak clustering in Gaussian random fields
No full textInternational audienceIn the peak approach, the formation sites of observable structures in the Universe are identified as peaks in the matter density field. The statistical properties of the clustering of peaks are particularly important in this respect. In this paper, we investigate the large-separation expansion of the correlation function of peaks in Gaussian random fields. The analytic formula up to third order is derived, and the resultant expression can be evaluated by a combination of one-dimensional fast Fourier transforms, which are evaluated very fast. The analytic formula obtained perturbatively in the large-separation limit is compared with a method of Monte Carlo integrations, and a complementarity between the two methods is demonstrated
Dataset in support of the thesis 'The Effect of High-Fat Diet During Mouse Preimplantation and Pregnancy-Lactation on Uterine Fluid Protein Composition, Maternal Metabolism and Offspring Health''
No full textDataset and omic data from Thesis entitled: The Effect of High-Fat Diet During Mouse Preimplantation and Pregnancy-Lactation on Uterine Fluid Protein Composition, Maternal Metabolism and Offspring Health. Author: Irene Peral-Sanchez
The added dataset included raw data generated from the period from Oct 2019 to December 2023.
As explained in the thesis, the data were analyzed using SPSS syntax (hierarchical model) and Prism. The omics data (RNA seq and Proteomics) were additionally studied by String and Gene Ontology, apart from R (collaborators).
If any other questions or clarification is needed, contact the author or main supervisor. </span
The cumulant generating function as a novel observable to cumulate weak lensing information
No full textBoyle A, Barthelemy A, Codis S, Habib S, Uhlemann C, Friedrich O. The cumulant generating function as a novel observable to cumulate weak lensing information. The Open Journal of Astrophysics. 2023;6.Key non-Gaussian properties of cosmological fields can be captured by their one-point statistics, providing a complement to two-point statistical measurements from power spectra or correlation functions. Large deviation theory can robustly predict the one-point statistics of cosmological density fields on mildly non-linear scales from first principles. It provides a direct prediction for the cumulant generating function (CGF) of such fields, from which a prediction for the more commonly used probability density function (PDF) is extracted through an inverse Laplace transform. For joint one-point statistics of multiple fields, the inverse Laplace transform rapidly becomes more cumbersome and computationally expensive. In this work, we demonstrate for the first time that the weak lensing CGF itself can be used as an observable that captures an equal amount of cosmological information to the PDF. While we use the weak-lensing convergence field as a simplistic and instructive example, this work is intended as a first step towards a cosmological analysis based on large deviation theory in the context of a nulling framework, which excludes contributions from small scales to facilitate highly accurate theoretical predictions. In this context, the method should be generally applicable for a multi-scale tomographic analysis of weak lensing and galaxy clustering
A theoretical view of the T-web statistical description of the cosmic web
No full textThe classification of the cosmic web into different environments is both a
tool to study in more detail the formation of halos and galaxies via the link
between their properties and the large-scale environment and as a class of
objects whose statistics contain cosmological information. In this paper, we
present an analytical framework to compute the probability of the different
environments in the cosmic web based on the T-web formalism that classifies
structures in four different classes (voids, walls, filaments, knots) by
studying the eigenvalues of the tidal tensor (Hessian of the gravitational
potential). This method relies on studying the eigenvalues of the tidal tensor
with respect to a given threshold and thus requires the knowledge of the JPDF
of those eigenvalues. We perform a change of variables in terms of minimally
correlated rotational invariants and we study their distribution in the linear
regime of structure formation, and in the quasi-linear regime with the help of
a Gram-Charlier expansion and tree-order Eulerian perturbation theory. This
expansion allows us to predict the probability of the different environments in
the density field at a given smoothing scale as a function of the chosen
threshold and redshift. We check the validity of our predictions by comparing
those predictions to measurements made in the N-body Quijote simulations. We
notably find that scaling the threshold value with the non-linear amplitude of
fluctuations allows us to capture almost entirely the redshift evolution of the
probability of the environments, even if we assume that the density field is
Gaussian (corresponding to the linear regime of structure formation). We also
show that adding mild non-Gaussian corrections in the form of third-order
cumulants of the field provides even more precise predictions for cosmic web
abundances up to scales as small as ~5 Mpc/h and redshifts down to z~0.Comment: 16 pages, 5 figure
On the projected mass distribution around galaxy clusters : a Lagrangian theory of harmonic power spectra
No full textInternational audienceAims. Gravitational lensing allows us to quantify the angular distribution of the convergence field around clusters of galaxies to constrain their connectivity to the cosmic web. We describe the corresponding theory in Lagrangian space in which analytical results can be obtained by identifying clusters to peaks in the initial field. Methods. We derived the three-point Gaussian statistics of a two-dimensional (2D) field and its first and second derivatives. The formalism allowed us to study the statistics of the field in a shell around a central peak, in particular its multipolar decomposition. Results. The peak condition is shown to significantly remove power from the dipolar contribution and to modify the monopole and quadrupole. As expected, higher order multipoles are not significantly modified by the constraint. Analytical predictions are successfully checked against measurements in Gaussian random fields. The effect of substructures and radial weighting is shown to be small and does not change the qualitative picture.The non-linear evolution is shown to induce a non-linear bias of all multipoles proportional to the cluster mass. Conclusions. We predict the Gaussian and weakly non-Gaussian statistics of multipolar moments of a 2D field around a peak as a proxy for the azimuthal distribution of the convergence field around a cluster of galaxies. A quantitative estimate of this multipolar decomposition of the convergence field around clusters in numerical simulations of structure formation and in observations will be presented in two forthcoming papers.Key words: large-scale structure of Universe / galaxies: clusters: general / gravitational lensing: weak / methods: analytical / methods: statistica
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