Search Results for author: Alexandre Refregier

Found 11 papers, 5 papers with code

Cosmology from Galaxy Redshift Surveys with PointNet

no code implementations22 Nov 2022 Sotiris Anagnostidis, Arne Thomsen, Tomasz Kacprzak, Tilman Tröster, Luca Biggio, Alexandre Refregier, Thomas Hofmann

In this work, we aim to improve upon two-point statistics by employing a \textit{PointNet}-like neural network to regress the values of the cosmological parameters directly from point cloud data.

Super-resolving Dark Matter Halos using Generative Deep Learning

1 code implementation11 Nov 2021 David Schaurecker, Yin Li, Jeremy Tinker, Shirley Ho, Alexandre Refregier

Generative deep learning methods built upon Convolutional Neural Networks (CNNs) provide a great tool for predicting non-linear structure in cosmology.

Cosmological constraints with deep learning from KiDS-450 weak lensing maps

no code implementations7 Jun 2019 Janis Fluri, Tomasz Kacprzak, Aurelien Lucchi, Alexandre Refregier, Adam Amara, Thomas Hofmann, Aurel Schneider

We present the cosmological results with a CNN from the KiDS-450 tomographic weak lensing dataset, constraining the total matter density $\Omega_m$, the fluctuation amplitude $\sigma_8$, and the intrinsic alignment amplitude $A_{\rm{IA}}$.

Cosmology and Nongalactic Astrophysics

Cosmological constraints from noisy convergence maps through deep learning

no code implementations23 Jul 2018 Janis Fluri, Tomasz Kacprzak, Aurelien Lucchi, Alexandre Refregier, Adam Amara, Thomas Hofmann

We find that, for a shape noise level corresponding to 8. 53 galaxies/arcmin$^2$ and the smoothing scale of $\sigma_s = 2. 34$ arcmin, the network is able to generate 45% tighter constraints.

Cosmology and Nongalactic Astrophysics

Fast Point Spread Function Modeling with Deep Learning

no code implementations23 Jan 2018 Jörg Herbel, Tomasz Kacprzak, Adam Amara, Alexandre Refregier, Aurelien Lucchi

We find that our approach is able to accurately reproduce the SDSS PSF at the pixel level, which, due to the speed of both the model evaluation and the parameter estimation, offers good prospects for incorporating our method into the $MCCL$ framework.

Radio frequency interference mitigation using deep convolutional neural networks

3 code implementations28 Sep 2016 Joel Akeret, Chihway Chang, Aurelien Lucchi, Alexandre Refregier

We employ a special type of Convolutional Neural Network, the U-Net, that enables the classification of clean signal and RFI signatures in 2D time-ordered data acquired from a radio telescope.

Instrumentation and Methods for Astrophysics

Approximate Bayesian Computation for Forward Modeling in Cosmology

1 code implementation27 Apr 2015 Joel Akeret, Alexandre Refregier, Adam Amara, Sebastian Seehars, Caspar Hasner

We first review the principles of ABC and discuss its implementation using a Population Monte-Carlo (PMC) algorithm and the Mahalanobis distance metric.

Cosmology and Nongalactic Astrophysics Instrumentation and Methods for Astrophysics Computation

Systematic Bias in Cosmic Shear: Beyond the Fisher Matrix

1 code implementation26 Oct 2007 Adam Amara, Alexandre Refregier

For a future DUNE-like full sky survey, we find that, for cases with mild redshift evolution, the variance of the additive systematic signal should be kept below 10^-7 to ensure biases on cosmological parameters that are sub-dominant to the statistical errors.

Polar Shapelets

1 code implementation24 Aug 2004 Richard Massey, Alexandre Refregier

The shapelets method for image analysis is based upon the decomposition of localised objects into a series of orthogonal components with convenient mathematical properties.

Image Manipulation

Weak Lensing Measurements: A Revisited Method and Application to HST Images

no code implementations7 May 1999 Jason Rhodes, Alexandre Refregier, Ed Groth

The weak distortions produced by gravitational lensing in the images of background galaxies provide a method to measure directly the distribution of mass in the universe.

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