CosmosClub Ariel SánchezDate: July 9th 2020, 10.00 a.m. Speaker: Ariel Sánchez (MPE Garching/ Max-Planck-Institut für extraterrestrische Physik ) Title: Let us bury the prehistoric h: arguments against using h−1Mpc units in observational cosmology Room: Zoom Meeting (connection details will be updated soon) Abstract It is common to express cosmological measurements in units of h^-1 Mpc. …
CosmosClub Erwan AllysDate: July 2nd 2020, 10.00 a.m. Speaker: Erwan Allys (ENS Paris / École Normale Supérieure, Laboratoire de Radioastronomie ) Title: The Wavelet Phase Harmonics, a new interpretable statistical description for analysis and synthesis of the LSS Room: Zoom Meeting (connection details will be updated soon) Abstract The statistical characterization of non-Gaussian fields is a …
Date: March 18th 2020, 10.30am Speaker: Florent Mertens (LERMA / Kapteyn Astronomical Institute) Title: The challenges of observing the Epoch of Reionization and Cosmic Dawn Room: Cassini Abstract Low-frequency observations of the redshifted 21cm line promise to open a new window onto the first billion years of cosmic history, allowing us to directly study the astrophysical …
Date: February 20th 2020, 10.00 am Room: Kepler Speaker: Céline Gouin (IAS, COSMIX) Title: Probing the azimuthal environment of galaxies around clusters. From cluster core to cosmic filaments Abstract: Galaxy clusters are connected at their peripheries to the large scale structures by cosmic filaments that funnel accreting material.Therefore, the vicinity of galaxy clusters are ideal places to …
Date: December 4rd 2019, 10.30am Speaker: Irène Waldspurger (CEREMADE, Université Paris-Dauphine) Title: Convex and non-convex algorithms for phase retrieval Room: Cassini Abstract Phase retrieval problems consist in recovering elements of a complex vector space from the modulus of their scalar product with a fixed family of measurement vectors. Traditional reconstruction algorithms rely on simple local optimization …
Testing Gravity and Dark Energy with Cosmology and Gravitational WavesDate: November 06th 2019, 15h30 Speaker: Miguel Zumalacarregui (UC Berkeley & IPhT Saclay) Title: Testing Gravity and Dark Energy with Cosmology and Gravitational Waves Room: Cassini Abstract Alternative theories of gravity may provide viable models of cosmic acceleration with the possibility of alleviating shortcomings of the standard …
Date: October 10th 2019, 15h00 Speaker: Fangchen Feng (Laboratoire Astroparticule & Cosmologie) Title: Reconstruction and characterisation of polarisations of a gravitational-wave signal Room: Kepler Abstract Polarisation properties of gravitational waves carry crucial information about the physics of gravitational sources (binary compact systems of black holes or neutron stars, etc. ) such as precession effects. In …
Date: October 22nd 2019, 11am Speaker: Catherine Heymans (ROE, Edinburgh) Title: low-z-vs-CMB tensions with KiDS and DES and photo-z calibration Room: Kepler Abstract Catherine Heymans will give a 15-20min introduction on recent work on low-z-vs-CMB tensions with KiDS and DES (https://arxiv.org/abs/1906.09262) and some more recent work on photo-z calibration. Then we will have a “bring a …
Date: July 12th 2019, 11am Speaker: Sebastian Rojas Gonzales (KU Leuven) Title: Gaussian processes for simulation optimization Room: Kepler Abstract The use of kriging metamodels (also known as gaussian processes) in simulation optimization has become increasingly popular during recent years. The majority of the algorithms so far uses the ordinary (deterministic) kriging approach for constructing …
Date: June 20th 2019, 11am Speaker: Doogesh Kodi Ramanah (IAP) Title: Fast complex dynamics emulators for cosmological inference Room: Cassini Abstract I will present an overview of our recent work in developing various aspects of Bayesian forward modelling machinery for an optimal exploitation of state-of-the-art galaxy redshift surveys. I will focus on the development of …
Date: June 13th 2019, 10:30am (/!\ unusual time) Speaker: Isabella Carucci (CosmoStat) Title: 21cm intensity mapping: using cosmic neutral hydrogen as tracer of large scale structure Room: Kepler Abstract This is an opportunity to introduce my past work to the group. I’ll start by briefly illustrating what we mean by intensity mapping (IM) and why …
Date: May 23rd 2019, 11am Speaker: Jean-Baptise Bayle (APC) Title: Space-based Detection of Gravitational Waves with LISA: Opening the Low-Frequency Part of the Gravitational Spectrum [slides] Room: Cassini Abstract Einstein’s theory of General Relativity offers a powerful picture of the world, where the gravitational force is only the consequence of the curvature of spacetime. Gravitational …
Date: May 20th 2019, 11am Presenters: Imane, Melis & Santiago Room: Kepler Papers Impact of Foregrounds on H1 Intensity Mapping Cross-Correlations with Optical Surveys – Melis [Annotated paper] Sparse BSS with Poisson noise or spectral variabilities – Imane [Slides] Flashtalk How to add your papers on the CosmoStat website – Santiago
Date: May 16th 2019, 4pm Speaker: Alejandro Borlaff (Instituto de Astrofísica de Canarias) Title: The missing light of the Hubble Ultra Deep Field Room: Kepler Abstract TBA
Date: April 25th 2019, 11am Speaker: Nial Jeffrey (UCL, currently visiting CosmoStat) Title: Deep Learning dark matter maps from Dark Energy Survey (DES) weak lensing data Room: Cassini Abstract Reconstructed density fields from weak lensing are rich in information about cosmological parameters and models of the Universe — including a large non-Gaussian component that cannot be …
Date: April 18th 2019, 2pm Presenters: Kamshat, Zaccharie & Sam Room: Copernic Papers First measurement of the Hubble constant from a dark standard siren using the Dark Energy Survey galaxies and the LIGO/Virgo binary-black-hole merger GW170814 – Kamshat [Highlighted paper] Learned Primal-dual Reconstruction – Zaccharie [Slides] [Highlighted paper] Flashtalk How to animate objects in Keynote …
Date: April 11th 2019, 11am Speaker: Antoine Labatie Title: Characterizing Well-behaved vs. Pathological Deep Neural Networks [paper] Room: Kepler Abstract We introduce a novel approach, requiring only mild assumptions, for the characterization of deep neural networks at initialization. Our approach applies both to fully-connected and convolutional networks and easily incorporates the commonly used techniques of …
Date: April 4th 2019, 11am Presenters: Christophe & Virginia Room: Kepler Papers Nonlinear Blind Source Separation for Sparse Sources – Christophe [Highlighted paper] [Slides] Likelihood-free inference workshop debriefing – Virginia [Slides]
Date: March 14th 2019, 11am Speaker: Adrien Picquenot (CEA Saclay) Title: Applying the GMCA to extended sources in X-Ray Astronomy Room: Kepler Abstract In high-energy astronomy, spectro-imaging instruments such as X-ray detectors allow investigation of the spatial and spectral properties of extended sources including galaxy clusters, galaxies, diffuse interstellar medium, supernova remnants and pulsar wind …
Date: March 7th 2019, 11am Presenters: Austin & Santiago Room: Kepler Papers Weak lensing cosmology with convolutional neural networks on noisy data – Austin [Highlighted paper] The Neutrino Puzzle: Anomalies, Interactions, and Cosmological Tensions – Santiago [Highlighted paper]
Date: February 28th 2019, 11am Speaker: Clément Leloup (CEA Paris-Saclay, DPhP) Title: Observational status of the Galileon model from cosmological data and gravitational waves [slides] Room: Cassini Abstract The Galileon model is a tensor-scalar theory of gravity which offers a theoretically viable explanation to the late acceleration of the Universe expansion and recovers General Relativity …
Date: February 11th 2019, 11am Speaker: Tobias Liaudat (ENSAE ParisTech) Title: Optimal Transport for Signed Measures [slides] Room: Cassini Abstract Optimal transport has become a mathematical gem at the interface of probability, analysis and optimization. It is a theory longly developed by the mathematician community, started by Monge and followed by Kantorovich which found applications …
Date: February 7th 2019, 11am Presenters: Fadi, Kostas & Martin Room: Cassini Papers The Sound of APALM Clapping: Faster Nonsmooth Nonconvex Optimization with Stochastic Asynchronous PALM- Kostas [Slides] Cosmological Constraints from Multiple Probes in the Dark Energy Survey – Martin [Highlighted paper] Flashtalk How to insert the CosmoStat signature in e-mails – Fadi
Date: Januray 24th 2019, 11am Presenters: Fadi, Morgan & Pol Room: Kepler Papers Deep Neuroevolution: Genetic Algorithms Are a Competitive Alternative for Training Deep Neural Networks for Reinforcement Learning – Fadi [Highlighted paper] [Slides] Links: https://www.samyzaf.com/ML/rl/qmaze.html https://www.youtube.com/watch?v=qv6UVOQ0F44 https://www.youtube.com/watch?v=gn4nRCC9TwQ https://www.youtube.com/watch?v=Aut32pR5PQA https://www.tutorialspoint.com/genetic_algorithms/genetic_algorithms_fundamentals.htm https://www.researchgate.net/figure/Iterative-scheme-of-a-genetic-algorithm_fig2_228847277 Weak-lensing shear estimates with general adaptive moments, and studies of bias by pixellation, PSF …
Date: January 14th 2018, 10am Speaker: Pol del Aguila Pla (KTH Royal Institute of Technology) Title: Cell detection by functional inverse diffusion and non-negative group sparsity – Biology, physics, math and engineering [slides] Room: Kepler Abstract Image-based immunoassays are used every day across the world to develop new drugs, diagnose diseases, and research the workings …
Date: October 16th 2018, 2pm Speaker: Sylvain Vanneste (LAL) Title: Detecting CMB B-modes Room: Kepler Abstract The discovery of the Cosmic Microwave Background (CMB) by Penzias and Wilson in 1964 was an important confirmation of the Big Bang theory. The CMB constitutes a background of photons emitted during the first instants of our Universe history, …
Date: November 7th 2018, 2pm Speaker: Jia Liu (Princeton University) Title: Cosmology in the nonlinear regime with massive neutrinos [slides] Room: Kepler Abstract The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, …
Date: October 9th 2018 Speaker: Chieh-An Lin (IfA, University of Edinburgh) Title: Predicting weak-lensing covariance with a fast simulator Weak lensing has been shown as an outstanding tool to constrain cosmology. The state-of-the-art studies have used the power spectrum and peak counts as estimators, and the combination of the two can break down parameter degeneracies …
Date: September 13th 2018 Speaker: Benjamin l’Huillier (Korea Astronomy and Space Science Institute) Title: Cosmological structure formation in LCDM and beyond: Testing LCDM with N-body simulations and advanced statistical methods [slides] The current concordance cosmological paradigm relies on a few assumptions: gravity is described by General Relativity, the Universe is Homogeneous and Isotropic on large …
Date: September 6th 2018 Speaker: Remy Joseph (EPFL) Title: Deblending methods for strong gravitational lensing PhD defense rehearsal.
Date: July 9th 2018 Speaker: Santiago Casas (CEA Saclay) Title: Dark Energy with Euclid Euclid is an ESA medium-class mission expected to launch in 2020 that will map the geometry of the Universe by imaging 10^9 galaxies and measuring 10^7 galaxy redshifts in 15000 square degrees of the sky. This will provide us detailed information …
Date: June 25th 2018 Speaker: Viviana Niro (University of Heidelberg) Title: Galaxy rotation curves in modified gravity models [slides] I’ll present the possibility that galaxy rotation curves can be explained in the framework of modified gravity models. A Yukawa term is considered in the gravitational potential and dark matter is included in the fit. Using …
Date: May 3rd 2018 Speaker: Alessio Spurio Mancini Title: Weak gravitational lensing as a (3D) probe of gravity Abstract Cosmic shear, the weak gravitational lensing effect caused by the large-scale structure, is one of the primary probes to test gravity on cosmological scales with current and future surveys. In particular, cosmic shear is sensitive to …
Date: April 13th 2018 Speaker: Benjamin Joachimi (University College London) Title: Cosmic shear cosmology – where we stand Abstract I will review the recent weak lensing cosmology results obtained by the ESO Kilo-Degree Survey, which display an intriguing, marginal discrepancy with the primary Planck CMB constraints on structure growth. Key analysis choices and challenges will …
Date: April 5th 2018 Speaker: Elena Sellentin (University of Geneva) Title: The skewed weak lensing likelihood: why biases arise, despite data and theory being sound Abstract We derive the essentials of the skewed weak lensing likelihood via a simple Hierarchical Model. Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails. We …
Date: March 28th 2018 Speaker: Anais Moller (Australian National University) Title: The next-generation of type Ia supernovae Dark Energy studies Abstract Currently Dark Energy studies with type Ia supernovae rely on a spectroscopically classified sample. The Dark Energy Survey (DES) is entering its last year of observations and a first cosmological analysis with the spectroscopically …
Date: March 7th 2018 Speaker: Nicolas Martinet (Universität Bonn) Title: Cosmological constraints from shear peaks in the Kilo Degree Survey (KiDS) Abstract The peak statistic in weak lensing reconstructed mass maps is a new powerful tool to probe cosmology. Peaks trace the Universe large scale structure, but on the contrary to the two-point correlation function …
Date: February 1st 2018 Speaker: Sandrine Codis (IAP) Title: Intrinsic alignments : theoretical and numerical insights Abstract In this talk, I will show how both dark matter and hydrodynamical simulations predict that the morphology of galaxies is correlated with the cosmic web. This large-scale coherence of galaxy shapes could possibly induce some non-negligible level of contamination …
Date: January 24th 2018 Speaker: Marco Crisostomi (CosmoStat/IPhT/LPT Orsay) Title: Modified gravity after GW170817 Journal club: Self-accelerating Universe in scalar-tensor theories after GW170817 Vainshtein mechanism after GW170817
Date: January 17th 2018 Speaker: François Orieux (L2S, Centrale-Supélec) Title: Semi-unsupervised Bayesian Convex Image Restoration with Location Mixture of Gaussian Abstract Convex image restoration is a major field in inverse problems. The problem is often addressed by hand-tuning hyper-parameters. We propose an incremental contribution about a Bayesian approach where a convex field is constructed via …
Date: December 8th 2017 Speaker: Emilie Chouzenoux (Université Paris-Est) Title: Proximity operator computation for video restoration [slides] Abstract Proximal methods have gained much interest for solving large-scale possibly non smooth optimization problems. When dealing with complicated convex functions, the expression of the proximity operator is however often non explicit and it thus needs to be determined …
Date: November 15th 2017 Speaker: Eleonora Villa (SISSA) Title: Theoretical systematics in galaxy clustering in LCDM and beyond Abstract We study the impact of neglecting lensing magnification in galaxy clustering analyses for future galaxy surveys, considering the ΛCDM model and two extensions: massive neutrinos and modifications of General Relativity. Our study focuses on the biases …
Note: this CosmoClub has been postponed to the 17th of January, 2018. Date: November 8th 2017 Speaker: François Orieux (L2S, Centrale-Supélec) Title: Semi-unsupervised Bayesian Convex Image Restoration with Location Mixture of Gaussian Abstract Convex image restoration is a major field in inverse problems. The problem is often addressed by hand-tuning hyper-parameters. We propose an incremental …
Date: October 19th 2017 Speaker: François Lanusse (Carnegie Mellon University) Title: Towards a better control of weak lensing systematics in the LSST era using Deep Learning Abstract In this talk, I will present several applications of the most recent advances made in the field of Deep Learning to some of the main sources of systematics …
Date: October 6th 2017 Speaker: Daniela Saadeh (University of Nottingham) Title: How isotropic is the Universe? Abstract A fundamental assumption of the standard model of cosmology is that the large-scale Universe is isotropic. Because of its centrality, it is essential to test this assumption. Breaking isotropy leads to Bianchi cosmologies, a set of solutions to …
Date: April 6th 2017 Speaker: Julie Josse (Ecole Polytechnique) Title: Missing data imputation using principal component methods Abstract Missing values are ubiquitous and can occur for plenty of reasons: machines that fail, survey participants who do not answer to all questions, etc. The problem of missing values is somehow exacerbated with the amount of available data: data …
Date: March 30th 2017 Speaker: Matthieu Simeoni (EPFL) Title: Bluebild: a Stable, Accurate and Efficient Imager for Radio Astronomy Abstract Radio astronomy imaging has been primarily focused on a planar approximation to a portion of the observed sphere, producing images of a fixed resolution. Historically, Fourier analysis played a pivotal role, with algorithmic modifications made to fit …
Date: March 27th 2017 Speaker: Francois Meyer (University of Colorado, Boulder/INRIA) Title: Detecting Structural Changes in Dynamic Community Networks Abstract The study of time-varying (dynamic) networks (graphs) is of fundamental importance for computer network analytics. Several methods have been proposed to detect the effect of significant structural changes in a time series of graphs.The main contribution …
Date: February 17th 2017 Speaker: Vivien Scottez (IAP) Title: Clustering-based Redshift estimation Abstract The clustering of galaxies has emerged as a powerful way to estimate the redshift distribution of a sample. I will briefly review how we can get access to redshift information from the crosscorrelation function. Then, using the MICE2 simulation I will present how we …
Date: February 2nd 2017 Speaker: Virginie Ollier (ENS Cachan/Supélec) Title: Robust Calibration of Radio Interferometers in Non-Gaussian Environment [slides] Abstract The development of new phased array systems in radio astronomy, as the low frequency array (LOFAR) and the square kilometre array (SKA), formed of a large number of small and flexible elementary antennas, has led to significant …
Date: December 1st 2017 Speaker: Emille Ishida (Université Clermont-Auvergne) Title: The Cosmostatistics Initiative (COIN) – reshaping scientific interdisciplinary collaborations [slides] Abstract The Cosmostatistics Initiative (COIN) is an international working group built under the auspices of the International Astrostatistics Association (IAA). Its goal is to propose an alternative approach to scientific collaboration while contributing to the establishment of …
Oct 20, 2016 Speaker Arnau Pujol (CosmoStat) Title Journal Club: A study of the sensitivity of shape measurements to the input parameters of weak lensing image simulations May 19, 2016 Speaker Carmelita Carbone (INAF) Title Clustering, lensing, and ISW/Rees-Sciama from the DEMNUni neutrino simulations Abstract I will present the first set of cosmological simulations produced within …
