CosmosClub

CosmosClub


  • 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