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Connected clustering denotes a family of constrained clustering problems in which we are given a distance metric and an undirected connectivity graph $G$ that can be completely unrelated to the metric. The aim is to partition the $n$…

Data Structures and Algorithms · Computer Science 2025-11-25 Jan Eube , Heiko Röglin

We use measurements of weak gravitational shear around a sample of massive galaxy clusters at z = 0.3 to constrain their average radial density profile. Our results are consistent with the density profiles of CDM halos in numerical…

Astrophysics · Physics 2007-05-23 H. Dahle

We study the stability of unitary quantum dynamics of composite systems (for example: central system + environment) with respect to weak interaction between the two parts. Unified theoretical formalism is applied to study different physical…

Quantum Physics · Physics 2009-11-07 Marko Znidaric , Tomaz Prosen

With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at $z\gtrsim2$. Evolutionary studies comparing these distant clusters to the clusters in our local universe depend…

We quantify the structure of a very large number of Galactic open clusters and look for evidence of mass segregation for the most massive stars in the clusters. We characterise the structure and mass segregation ratios of 1276 clusters in…

Astrophysics of Galaxies · Physics 2017-10-30 Sami Dib , Stefan Schmeja , Richard J. Parker

The existence of the three most massive clusters of galaxies observed so far at z>0.5 is used to constrain the mass density parameter of the universe, Omega, and the amplitude of mass fluctuations, sigma_8. We find Omega=0.2 (+0.3,-0.1),…

Astrophysics · Physics 2011-05-05 Neta A. Bahcall , Xiaohui Fan

Given a trajectory $T$ and a distance $\Delta$, we wish to find a set $C$ of curves of complexity at most $\ell$, such that we can cover $T$ with subcurves that each are within Fr\'echet distance $\Delta$ to at least one curve in $C$. We…

Computational Geometry · Computer Science 2025-05-26 Ivor van der Hoog , Thijs van der Horst , Tim Ophelders

We study the efficient learnability of high-dimensional Gaussian mixtures in the outlier-robust setting, where a small constant fraction of the data is adversarially corrupted. We resolve the polynomial learnability of this problem when the…

Data Structures and Algorithms · Computer Science 2020-05-14 Ilias Diakonikolas , Samuel B. Hopkins , Daniel Kane , Sushrut Karmalkar

We present the first measurement of the mass function of galaxy clusters based directly on cluster masses derived from observations of weak gravitational lensing. To investigate the degree of sample incompleteness resulting from the X-ray…

Astrophysics · Physics 2009-02-06 H. Dahle

The surface mass density of a cluster of galaxies, and thus its total mass, can be estimated from its lens magnification. The magnification can be determined from the variation in number counts of its background galaxies. In the weak…

Astrophysics · Physics 2009-10-30 Eelco van Kampen

In 1998, Leclerc and Zelevinsky introduced the notion of weakly separated collections of subsets of the ordered $n$-element set $[n]$ (using this notion to give a combinatorial characterization for quasi-commuting minors of a quantum…

Combinatorics · Mathematics 2016-09-20 Vladimir I. Danilov , Alexander V. Karzanov , Gleb A. Koshevoy

The total mass of clusters of galaxies is a key parameter to study massive halos. It relates to numerous gravitational and baryonic processes at play in the framework of large scale structure formation, thus rendering its determination…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 G. Foëx , G. Soucail , E. Pointecouteau , M. Arnaud , M. Limousin , G. W. Pratt

In this paper, we study gapsets and we focus on obtaining information on how the maximum distance between to consecutive elements influences the behaviour of the set. In particular, we prove that the cardinality of the set of gapsets with…

Combinatorics · Mathematics 2022-01-25 Gilberto B. Almeida Filho , Matheus Bernardini

Weak lensing is one of the best available diagnostic tools to measure the total density profiles of distant clusters of galaxies. Unfortunately, it suffers from the well-known mass-sheet degeneracy, so that weak lensing analyses cannot lead…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Alessandro Sonnenfeld , Giuseppe Bertin , Marco Lombardi

We give the first $2$-approximation algorithm for the cluster vertex deletion problem. This is tight, since approximating the problem within any constant factor smaller than $2$ is UGC-hard. Our algorithm combines the previous approaches,…

Combinatorics · Mathematics 2021-10-19 Manuel Aprile , Matthew Drescher , Samuel Fiorini , Tony Huynh

A locally compact group $ G $ is discrete if and only if the Fourier algebra $ A(G) $ has a non-zero (weakly) compact multiplier. We partially extend this result to the setting of ultraspherical hypergroups. Let $H$ be an ultraspherical…

Functional Analysis · Mathematics 2019-07-09 Reza Esmailvandi , Mehdi Nemati

We present a survey of mass profiles and mass-to-light ratios of eight typical galaxy clusters at a common redshift (z ~ 0.2). We use weak gravitational lensing as a probe because it is unique in avoiding any assumptions about the dynamical…

A novel nonparametric clustering algorithm is proposed using the interpoint distances between the members of the data to reveal the inherent clustering structure existing in the given set of data, where we apply the classical nonparametric…

Methodology · Statistics 2024-09-02 Soumita Modak

Good a-priori bounds on the smallest pairwise distance $r_{\rm{{min}}}(\mbox{LJ}_N^{\rm{gmin}})$ for a three-dimensional (3D) Lennard-Jones $N$-body cluster of globally minimal energy can significantly reduce the computational search space…

Atomic and Molecular Clusters · Physics 2025-11-20 Michael K. -H. Kiessling , David J. Wales

The weak lensing (WL) distortions of distant galaxy images are sensitive to neutrino masses by probing the suppression effect on clustering strengths of total matter in large-scale structure. We use the latest measurement of WL…

Astrophysics · Physics 2010-04-21 Kiyotomo Ichiki , Masahiro Takada , Tomo Takahashi
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