35,052 research outputs found
Metric structures in L_1: Dimension, snowflakes, and average distortion
We study the metric properties of finite subsets of L_1. The analysis of such
metrics is central to a number of important algorithmic problems involving the
cut structure of weighted graphs, including the Sparsest Cut Problem, one of
the most compelling open problems in the field of approximation algorithms.
Additionally, many open questions in geometric non-linear functional analysis
involve the properties of finite subsets of L_1.Comment: 9 pages, 1 figure. To appear in European Journal of Combinatorics.
Preliminary version appeared in LATIN '0
Metric-measure boundary and geodesic flow on Alexandrov spaces
We relate the existence of many infinite geodesics on Alexandrov spaces to a
statement about the average growth of volumes of balls. We deduce that the
geodesic flow exists and preserves the Liouville measure in several important
cases. The developed analytic tool has close ties to integral geometry
Periodicity and Circle Packing in the Hyperbolic Plane
We prove that given a fixed radius , the set of isometry-invariant
probability measures supported on ``periodic'' radius -circle packings of
the hyperbolic plane is dense in the space of all isometry-invariant
probability measures on the space of radius -circle packings. By a periodic
packing, we mean one with cofinite symmetry group. As a corollary, we prove the
maximum density achieved by isometry-invariant probability measures on a space
of radius -packings of the hyperbolic plane is the supremum of densities of
periodic packings. We also show that the maximum density function varies
continuously with radius.Comment: 25 page
Euclidean versus hyperbolic congestion in idealized versus experimental networks
This paper proposes a mathematical justification of the phenomenon of extreme
congestion at a very limited number of nodes in very large networks. It is
argued that this phenomenon occurs as a combination of the negative curvature
property of the network together with minimum length routing. More
specifically, it is shown that, in a large n-dimensional hyperbolic ball B of
radius R viewed as a roughly similar model of a Gromov hyperbolic network, the
proportion of traffic paths transiting through a small ball near the center is
independent of the radius R whereas, in a Euclidean ball, the same proportion
scales as 1/R^{n-1}. This discrepancy persists for the traffic load, which at
the center of the hyperbolic ball scales as the square of the volume, whereas
the same traffic load scales as the volume to the power (n+1)/n in the
Euclidean ball. This provides a theoretical justification of the experimental
exponent discrepancy observed by Narayan and Saniee between traffic loads in
Gromov-hyperbolic networks from the Rocketfuel data base and synthetic
Euclidean lattice networks. It is further conjectured that for networks that do
not enjoy the obvious symmetry of hyperbolic and Euclidean balls, the point of
maximum traffic is near the center of mass of the network.Comment: 23 pages, 4 figure
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