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Clusters of galaxies, the most massive virialized systems known, provide a powerful tool for studying the structure, the mass density, and the cosmology of our universe. Clusters furnish one of the best estimates of the dynamical mass…

Astrophysics · Physics 2007-05-23 Neta A. Bahcall

Weak lensing applied to deep optical images of clusters of galaxies provides a powerful tool to reconstruct the distribution of the gravitating mass associated to these structures. We use the shear signal extracted by an analysis of deep…

We investigate the problem of exact cluster recovery using oracle queries. Previous results show that clusters in Euclidean spaces that are convex and separated with a margin can be reconstructed exactly using only $O(\log n)$ same-cluster…

Machine Learning · Computer Science 2021-07-14 Marco Bressan , Nicolò Cesa-Bianchi , Silvio Lattanzi , Andrea Paudice

We present two weak lensing reconstructions of the nearby ($z_{cl}=0.055$) merging cluster Abell 3667, based on observations taken $\sim 1$ year apart under different seeing conditions. This is the lowest redshift cluster with a weak…

Astrophysics · Physics 2009-10-31 M. Joffre , P. Fischer , J. Frieman , T. McKay , J. Mohr , R. Nichol , D. Johnston , E. Sheldon , G. Berstein

The increasing needs of clustering massive datasets and the high cost of running clustering algorithms poses difficult problems for users. In this context it is important to determine if a data set is clusterable, that is, it may be…

Machine Learning · Computer Science 2020-01-08 Dan Simovici , Kaixun Hua

Some years ago we proposed a new approach to the analysis of galaxy and cluster correlations based on the concepts and methods of modern statistical Physics. This led to the surprising result that galaxy correlations are fractal and not…

Astrophysics · Physics 2017-05-31 F. Sylos Labini , M. Montuori , L. Pietronero

Different types of two- and three-dimensional representations of a finite metric space are studied that focus on the accurate representation of the linear order among the distances rather than their actual values. Lower and upper bounds for…

Combinatorics · Mathematics 2007-05-23 Jobst Heitzig

In the kernel clustering problem we are given a large $n\times n$ positive semi-definite matrix $A=(a_{ij})$ with $\sum_{i,j=1}^na_{ij}=0$ and a small $k\times k$ positive semi-definite matrix $B=(b_{ij})$. The goal is to find a partition…

Data Structures and Algorithms · Computer Science 2008-12-09 Subhash Khot , Assaf Naor

Stars in open clusters are powerful probes of the intervening Galactic magnetic field, via background starlight polarimetry, because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31…

Solar and Stellar Astrophysics · Physics 2015-10-14 Sadia Hoq , Dan Clemens

An irreducible algebraic decomposition $\cup_{i=0}^{d}X_i=\cup_{i=0}^{d} (\cup_{j=1}^{d_i}X_{ij})$ of an affine algebraic variety X can be represented as an union of finite disjoint sets $\cup_{i=0}^{d}W_i=\cup_{i=0}…

Algebraic Geometry · Mathematics 2010-10-18 Shawki Al-Rashed , Gerhard Pfister

Let $X$ be a Banach space and $\mu$ a probability measure. A set $K \subseteq L^1(\mu,X)$ is said to be a $\delta\mathcal{S}$-set if it is uniformly integrable and for every $\delta>0$ there is a weakly compact set $W \subseteq X$ such that…

Functional Analysis · Mathematics 2016-11-23 José Rodríguez

The early evolution of massive cluster progenitors is poorly understood. We investigate the fragmentation properties from 0.3 pc to 0.06 pc scales of a homogenous sample of infrared-quiet massive clumps within 4.5 kpc selected from the…

The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak…

We propose counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters. Because peaks can be identified in two-dimensional WL maps directly, they can…

Cosmology and Nongalactic Astrophysics · Physics 2010-04-06 Jan M. Kratochvil , Zoltán Haiman , Morgan May

In this letter we consider the ensemble of codes formed by the serial concatenation of a Hamming code and two accumulate codes. We show that this ensemble is asymptotically good, in the sense that most codes in the ensemble have minimum…

Information Theory · Computer Science 2009-05-29 Alexandre Graell i Amat , Raphael Le Bidan

Galaxy clusters provide a unique probe of the late-time cosmic structure and serve as a powerful independent test of the $\Lambda$CDM model. This work presents the first set of cosmological constraints derived with ~16,000 optically…

Galaxy clusters are the most massive gravitationally bound systems consisting of dark matter, hot baryonic gas and stars. They play an important role in observational cosmology and galaxy evolution studies. We develop a deep learning model…

Astrophysics of Galaxies · Physics 2024-05-16 S. Voskresenskaia , A. Meshcheryakov , N. Lyskova

Centroid based clustering methods such as k-means, k-medoids and k-centers are heavily applied as a go-to tool in exploratory data analysis. In many cases, those methods are used to obtain representative centroids of the data manifold for…

Machine Learning · Computer Science 2022-06-16 Ahmed Imtiaz Humayun , Randall Balestriero , Anastasios Kyrillidis , Richard Baraniuk

We consider an infinite-dimensional stochastic clustering model on $\mathbb{R}$. In discrete time, each point of a unit-intensity simple point process moves halfway toward either of its left or right neighbors, chosen uniformly at random.…

Probability · Mathematics 2026-03-10 Partha S. Dey , S. Rasoul Etesami , Aditya S. Gopalan

Aims: We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. Methods: The eleven clusters in our sample are all X-ray…

Astrophysics · Physics 2009-11-13 S. Bardeau , G. Soucail , J. P. Kneib , O. Czoske , H. Ebeling , P. Hudelot , I. Smail , G. P. Smith