Some remarks on the asymptotic behavor of toeplitz determinants

In order to optimize the stability regions we construct families of k multi-step methods with free parameters and of order k+1. We exhibit parameters for which the real interval of stability is arbitrarly large and using the Flexible Tolerance Method we show how these parameters optimize - under a predefined criterion - the stability region. Computational experience, while limited, has indicated that the procedure is efficient     

The forward problem for the electromagnetic Helmholtz equation with critical singularities

We study the forward problem of the magnetic Schrödinger operator with potentials that have a strong singularity at the origin. We obtain new resolvent estimates and give some applications on the spectral measure and on the solutions of the associated evolution problem.     

Local existence and uniqueness for the hydrostatic Euler equations on a bounded domain

We address the question of well-posedness in spaces of analytic functions for the Cauchy problem for the hydrostatic incompressible Euler equations (inviscid primitive equations) on domains with boundary. By a suitable extension of the Cauchy-Kowalewski theorem we construct a locally in time, unique, real-analytic solution and give an explicit rate of decay of the radius of real-analyticity.     

Existence and uniqueness of positive solutions to the boundary blow-up problem for an elliptic system

An elliptic system is considered in a smooth bounded domain, subject to Dirichlet boundary conditions of three different types. Based on the construction of certain upper and sub-solutions, we obtain some conditions on the parameters ai,bi,ci (i=1,2) and the exponents m,n,p,q to ensure the existence of positive solutions. Furthermore, uniqueness and boundary behavior of positive solutions is also discussed.     

Optimal uniqueness theorems and exact blow-up rates of large solutions

In this paper, we prove some optimal uniqueness results for large solutions of a canonical class of semilinear equations under minimal regularity conditions on the weight function in front of the non-linearity and combine these results with the localization method introduced in [López-Gómez, The boundary blow-up rate of large solutions, J. Differential Equations 195 (2003) 25-45] to prove that any large solution L of Δu=a(x)u^p, p>1, a>0, must satisfy

     

Homotopy uniqueness ofBG 2

We prove that the homotopy type ofBG ₂ is determined by its mod 2 cohomology as well as by its Weyl group data. The author is partially supported by DGICYT grant PB94-0725.     

Characteristic expansions and multiplicative addition theorems

The notions of -polynomial expansion % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqefeKCPfgBaG% qbciaa-DgacaGGOaWexLMBb50ujbqeguuDJXwAKbacgiGae4hEaGNa% ey4kaSsefCuzVj3zPfgaiCGacaqF5bGaaiykaiabg2da9iaa-Dgaca% GGOaGae4hEaGNaaiykaiabgUcaRiaa-DgacaGGOaGaa0xEaiaacMca% cqGHRaWkdaaeqbqaaiaadchadaWgaaWcbaGaamOBaaqabaGccaGGOa% Gaeqy1dOMaaiikaiab+Hha4jaacMcacaGGPaWaaSaaaeaacaqF5bWa% aWbaaSqabeaacaqFUbaaaaGcbaGaamOBaiaacgcaaaGaey4kaSIaam% OCaiaacIcacqGF4baEcqGFSaalcaqF5bGaaiykaiaacYcaaSqaaiaa% d6gatuuDJXwAK1uy0HMmaeXbfv3ySLgzG0uy0HgiuD3BaGacciab8v% MifkaaigdaaeqaniabggHiLdaaaa!7116!\[g(x + y) = g(x) + g(y) + \sum\limits_{n \geqslant 1} {p_n (\varphi (x))\frac{{y^n }}{{n!}} + r(x,y),} \] and multiplicative addition theorems % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyOeI0YaaS% aaaeaacaaIXaaabaGaamyAaaaadaWcaaqaaiabgkGi2cqaaiabgkGi% 2kaadshaaaqeduuDJXwAKbYu51MyVXgaiuaacqWFvpGAcaWG0bGaey% ypa0JaamisamaaBaaaleaacaGGOaaabeaakmaaBaaaleaacaGGPaaa% beaakiab-v9aQjaadshaaaa!4A8D!\[ - \frac{1}{i}\frac{\partial }{{\partial t}}\varphi t = H_( _) \varphi t\] are introduced and characterization of some -polynomial expansions and multiplicative addition theorems are obtained.Sponsored by the International Science Foundation (Soros) Grant M3Z00 and by Russian Foundation of Fundamental Research 94-01-0144.     

Asymptotic existence theorems for formal power series whose coefficients satisfy certain partial differential recursions

We study power series whose coefficients are holomorphic functions of another complex variable and a nonnegative real parameter s, and are given by a differential recursion equation. For positive integer s, series of this form naturally occur as formal solutions of some partial differential equations with constant coefficients, while for s=0 they satisfy certain perturbed linear ordinary differential equations. For arbitrary s?0, these series solve a differential-integral equation. Such power series, in general, are not multisummable. However, we shall prove existence of solutions of the same differential-integral equation that in sectors of, in general, maximal opening have the formal series as their asymptotic expansion. Furthermore, we shall indicate that the solutions so obtained can be related to one another in a fairly explicit manner, thus exhibiting a Stokes phenomenon.     

Existence, uniqueness and stability of travelling waves in a discrete reaction-diffusion monostable equation with delay

In this paper, we study the existence, uniqueness and asymptotic stability of travelling wavefronts of the following equation:

u_t(x,t)=D[u(x+1,t)+u(x-1,t)-2u(x,t)]-du(x,t)+b(u(x,t-r)),     

On the existence of positive solution for a kind of multi-point boundary value problem at resonance

This paper concerns the existence of positive solution for a class of second-order m-point boundary value problems under different resonant conditions. By using the Leggett-Williams norm-type theorem due to O’Regan and Zima, we obtain the existence of positive solution. An example is given to demonstrate the main results.     

The existence of mild and classical solutions for a second-order abstract fractional problem

In this paper we consider a second-order abstract problem involving derivatives of non-integer order. The existence and uniqueness of mild and classical solutions are established in appropriate spaces under weak assumptions.     

Equilibrium existence theorems in KKM spaces

An abstract convex space satisfying the KKM principle is called a KKM space. This class of spaces contains G$G$-convex spaces properly. In this work, we show that a large number of results in KKM theory on G$G$-convex spaces also hold on KKM spaces. Examples of such results are theorems of Sperner and Alexandroff–Pasynkoff, Fan–Browder type fixed point theorems, Horvath type fixed point theorems, Ky Fan type minimax inequalities, variational inequalities, von Neumann type minimax theorems, Nash type equilibrium theorems, and Himmelberg type fixed point theorems.     

Theorem about existence and uniqueness of continuous solution of nonlocal problem for nonlinear hyperbolic equation

The aim of the paper is to give a theorem about the existence and uniqueness of the continuous solution of a non-linear differential hyperbolic problem with a nonlocal condition in a bounded domain. The Banach theorem about the fixed point is used to prove the existence and uniqueness of the problem considered. The results obtained in this paper can be applied in the theory of elasticity with better effect than the analogous known result with the classical initial condition.     

A necessary and sufficient condition for the existence of positive solutions to a kind of singular three-point boundary value problem

In this paper, we are concerned with the following three point boundary value problem