37 research outputs found
Hyperbolic polyhedral surfaces with regular faces
We study hyperbolic polyhedral surfaces with faces isometric to regular
hyperbolic polygons satisfying that the total angles at vertices are at least
The combinatorial information of these surfaces is shown to be
identified with that of Euclidean polyhedral surfaces with negative
combinatorial curvature everywhere. We prove that there is a gap between areas
of non-smooth hyperbolic polyhedral surfaces and the area of smooth hyperbolic
surfaces. The numerical result for the gap is obtained for hyperbolic
polyhedral surfaces, homeomorphic to the double torus, whose 1-skeletons are
cubic graphs.Comment: 23 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1804.1103
Correlation matrix of equi-correlated normal population: fluctuation of the largest eigenvalue, scaling of the bulk eigenvalues, and stock market
Given an -dimensional sample of size and form a sample correlation
matrix . Suppose that and tend to infinity with
converging to a fixed finite constant . If the population is a factor
model, then the eigenvalue distribution of almost surely converges
weakly to Mar\v{c}enko-Pastur distribution such that the index is and the
scale parameter is the limiting ratio of the specific variance to the -th
variable . For an -dimensional normal population with
equi-correlation coefficient , which is a one-factor mode, for the
largest eigenvalue of , we prove that
converges to the equi-correlation coefficient almost surely. These
results suggest an important role of an equi-correlated normal population and a
factor model in (Laloux et al. Random matrix theory and financial correlations,
Int. J. Theor. Appl. Finance, 2000): the histogram of the eigenvalue of sample
correlation matrix of the returns of stock prices fits the density of
Mar\v{c}enko-Pastur distribution of index and scale parameter
. Moreover, we provide the limiting distribution of the largest
eigenvalue of a sample covariance matrix of an equi-correlated normal
population. We discuss the phase transition as to the decay rate of the
equi-correlation coefficient in
Spherical tilings by congruent quadrangles : forbidden cases and substructures
In this article we show the non-existence of a class of spherical tilings by congruent quadrangles. We also prove several forbidden substructures for spherical tilings by congruent quadrangles. These are results that will help to complete of the classification of spherical tilings by congruent quadrangles
The Confluent Terminating Context-Free Substitutive Rewriting System for the lambda-Calculus with Surjective Pairing and Terminal Type
For the lambda-calculus with surjective pairing and terminal type, Curien and Di Cosmo, inspired by Knuth-Bendix completion, introduced a confluent rewriting system of the naive rewriting system. Their system is a confluent (CR) rewriting system stable under contexts. They left the strong normalization (SN) of their rewriting system open. By Girard\u27s reducibility method with restricting reducibility theorem, we prove SN of their rewriting, and SN of the extensions by polymorphism and (terminal types caused by parametric polymorphism). We extend their system by sum types and eta-like reductions, and prove the SN. We compare their system to type-directed expansions