A Sharp Threshold for Random Graphs with a Monochromatic Triangle in Every Edge Coloring

A Sharp Threshold for Random Graphs with a Monochromatic Triangle in Every Edge Coloring
Author: Ehud Friedgut
Publisher: American Mathematical Soc.
Total Pages: 80
Release: 2006
Genre: Mathematics
ISBN: 0821838253

Let $\cal{R}$ be the set of all finite graphs $G$ with the Ramsey property that every coloring of the edges of $G$ by two colors yields a monochromatic triangle. In this paper the authors establish a sharp threshold for random graphs with this property. Let $G(n, p)$ be the random graph on $n$ vertices with edge probability $p$. The authors prove that there exists a function $\widehat c=\widehat c(n)=\Theta(1)$ such that for any $\varepsilon > 0$, as $n$ tends to infinity, $Pr\left[G(n, (1-\varepsilon)\widehat c/\sqrt{n}) \in \cal{R} \right] \rightarrow 0$ and $Pr \left[ G(n, (1]\varepsilon)\widehat c/\sqrt{n}) \in \cal{R}\ \right] \rightarrow 1.$. A crucial tool that is used in the proof and is of independent interest is a generalization of Szemeredi's Regularity Lemma to a certain hypergraph setti

Exceptional Vector Bundles, Tilting Sheaves and Tilting Complexes for Weighted Projective Lines

Exceptional Vector Bundles, Tilting Sheaves and Tilting Complexes for Weighted Projective Lines
Author: Hagen Meltzer
Publisher: American Mathematical Soc.
Total Pages: 154
Release: 2004
Genre: Mathematics
ISBN: 082183519X

Deals with weighted projective lines, a class of non-commutative curves modelled by Geigle and Lenzing on a graded commutative sheaf theory. They play an important role in representation theory of finite-dimensional algebras; the complexity of the classification of coherent sheaves largely depends on the genus of these curves.

The Second Duals of Beurling Algebras

The Second Duals of Beurling Algebras
Author: Harold G. Dales
Publisher: American Mathematical Soc.
Total Pages: 206
Release: 2005
Genre: Mathematics
ISBN: 0821837745

Let $A$ be a Banach algebra, with second dual space $A""$. We propose to study the space $A""$ as a Banach algebra. There are two Banach algebra products on $A""$, denoted by $\,\Box\,$ and $\,\Diamond\,$. The Banach algebra $A$ is Arens regular if the two products $\Box$ and $\Diamond$ coincide on $A""$.

Mutually Catalytic Super Branching Random Walks: Large Finite Systems and Renormalization Analysis

Mutually Catalytic Super Branching Random Walks: Large Finite Systems and Renormalization Analysis
Author: J. T. Cox
Publisher: American Mathematical Soc.
Total Pages: 114
Release: 2004
Genre: Mathematics
ISBN: 0821835424

Studies the evolution of the large finite spatial systems in size-dependent time scales and compare them with the behavior of the infinite systems, which amounts to establishing the so-called finite system scheme. This title introduces the concept of a continuum limit in the hierarchical mean field limit.

Kahler Spaces, Nilpotent Orbits, and Singular Reduction

Kahler Spaces, Nilpotent Orbits, and Singular Reduction
Author: Johannes Huebschmann
Publisher: American Mathematical Soc.
Total Pages: 110
Release: 2004
Genre: Mathematics
ISBN: 0821835726

For a stratified symplectic space, a suitable concept of stratified Kahler polarization encapsulates Kahler polarizations on the strata and the behaviour of the polarizations across the strata and leads to the notion of stratified Kahler space which establishes an intimate relationship between nilpotent orbits, singular reduction, invariant theory, reductive dual pairs, Jordan triple systems, symmetric domains, and pre-homogeneous spaces: The closure of a holomorphic nilpotent orbit or, equivalently, the closure of the stratum of the associated pre-homogeneous space of parabolic type carries a (positive) normal Kahler structure. In the world of singular Poisson geometry, the closures of principal holomorphic nilpotent orbits, positive definite hermitian JTS's, and certain pre-homogeneous spaces appear as different incarnations of the same structure. The closure of the principal holomorphic nilpotent orbit arises from a semisimple holomorphic orbit by contraction. Symplectic reduction carries a positive Kahler manifold to a positive normal Kahler space in such a way that the sheaf of germs of polarized functions coincides with the ordinary sheaf of germs of holomorphic functions. Symplectic reduction establishes a close relationship between singular reduced spaces and nilpotent orbits of the dual groups. Projectivization of holomorphic nilpotent orbits yields exotic (positive) stratified Kahler structures on complex projective spaces and on certain complex projective varieties including complex projective quadrics. The space of (in general twisted) representations of the fundamental group of a closed surface in a compact Lie group or, equivalently, a moduli space of central Yang-Mills connections on a principal bundle over a surface, inherits a (positive) normal (stratified) Kahler structure. Physical examples are provided by certain reduced spaces arising from angular momentum zero.

Kleinian Groups which Are Limits of Geometrically Finite Groups

Kleinian Groups which Are Limits of Geometrically Finite Groups
Author: Ken'ichi Ōshika
Publisher: American Mathematical Soc.
Total Pages: 136
Release: 2005
Genre: Mathematics
ISBN: 0821837729

Ahlfors conjectured in 1964 that the limit set of every finitely generated Kleinian group either has Lebesgue measure $0$ or is the entire $S^2$. This title intends to prove that this conjecture is true for purely loxodromic Kleinian groups which are algebraic limits of geometrically finite groups.

Entropy Bounds and Isoperimetry

Entropy Bounds and Isoperimetry
Author: Serguei Germanovich Bobkov
Publisher: American Mathematical Soc.
Total Pages: 88
Release: 2005
Genre: Computers
ISBN: 082183858X

In these memoirs Bobkov and Zegarlinski describe interesting developments in infinite dimensional analysis that moved it away from experimental science. Here they also describe Poincar -type inequalities, entropy and Orlicz spaces, LSq and Hardy-type inequalities on the line, probability measures satisfying LSq inequalities on the real line, expo

Hilbert Modular Forms: mod $p$ and $p$-Adic Aspects

Hilbert Modular Forms: mod $p$ and $p$-Adic Aspects
Author: Fabrizio Andreatta
Publisher: American Mathematical Soc.
Total Pages: 114
Release: 2005
Genre: Mathematics
ISBN: 0821836099

We study Hilbert modular forms in characteristic $p$ and over $p$-adic rings. In the characteristic $p$ theory we describe the kernel and image of the $q$-expansion map and prove the existence of filtration for Hilbert modular forms; we define operators $U$, $V$ and $\Theta_\chi$ and study the variation of the filtration under these operators. Our methods are geometric - comparing holomorphic Hilbert modular forms with rational functions on a moduli scheme with level-$p$ structure, whose poles are supported on the non-ordinary locus.In the $p$-adic theory we study congruences between Hilbert modular forms. This applies to the study of congruences between special values of zeta functions of totally real fields. It also allows us to define $p$-adic Hilbert modular forms 'a la Serre' as $p$-adic uniform limit of classical modular forms, and compare them with $p$-adic modular forms 'a la Katz' that are regular functions on a certain formal moduli scheme. We show that the two notions agree for cusp forms and for a suitable class of weights containing all the classical ones. We extend the operators $V$ and $\Theta_\chi$ to the $p$-adic setting.

Classification and Probabilistic Representation of the Positive Solutions of a Semilinear Elliptic Equation

Classification and Probabilistic Representation of the Positive Solutions of a Semilinear Elliptic Equation
Author: Benoît Mselati
Publisher: American Mathematical Soc.
Total Pages: 146
Release: 2004
Genre: Mathematics
ISBN: 0821835092

Concerned with the nonnegative solutions of $\Delta u = u^2$ in a bounded and smooth domain in $\mathbb{R}^d$, this title intends to prove that they are uniquely determined by their fine trace on the boundary as defined in [DK98a], answering a major open question of [Dy02].