110 research outputs found
Delivering safe and effective hemodialysis in patients with suspected or confirmed COVID-19 infection : a single-center perspective from Italy
MulGuisin, a Topological Network Finder and its Performance on Galaxy Clustering
We introduce a new clustering algorithm, MulGuisin (MGS), that can identify
distinct galaxy over-densities using topological information from the galaxy
distribution. This algorithm was first introduced in an LHC experiment as a Jet
Finder software, which looks for particles that clump together in close
proximity. The algorithm preferentially considers particles with high energies
and merges them only when they are closer than a certain distance to create a
jet. MGS shares some similarities with the minimum spanning tree (MST) since it
provides both clustering and network-based topology information. Also, similar
to the density-based spatial clustering of applications with noise (DBSCAN),
MGS uses the ranking or the local density of each particle to construct
clustering. In this paper, we compare the performances of clustering algorithms
using controlled data and some realistic simulation data as well as the SDSS
observation data, and we demonstrate that our new algorithm find networks most
efficiently and it defines galaxy networks in a way that most closely resembles
human vision.Comment: 15 pages,12 figure
Graph Database Solution for Higher Order Spatial Statistics in the Era of Big Data
We present an algorithm for the fast computation of the general -point
spatial correlation functions of any discrete point set embedded within an
Euclidean space of . Utilizing the concepts of kd-trees and graph
databases, we describe how to count all possible -tuples in binned
configurations within a given length scale, e.g. all pairs of points or all
triplets of points with side lengths . Through bench-marking we show
the computational advantage of our new graph based algorithm over more
traditional methods. We show that all 3-point configurations up to and beyond
the Baryon Acoustic Oscillation scale (200 Mpc in physical units) can be
performed on current SDSS data in reasonable time. Finally we present the first
measurements of the 4-point correlation function of 0.5 million SDSS
galaxies over the redshift range .Comment: 9 pages, 8 figures, submitte
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