Green functions and eigenfunction expansions for the square of the Laplace–Beltrami operator on plane domains

For a certain class of domains Ω⊂ℂ with smooth boundary and Δtilde;_Ω=w ²Δ the Laplace–Beltrami operator with respect to the Poincaré metric ds ²=w(z)^-2 dz dz on Ω, we (1) show that the Green function for the biharmonic operator Δtilde;_Ω ², with Dirichlet boundary data, is positive on Ω×Ω; and (2) obtain an eigenfunction expansion for the operator Δtilde;_Ω, which reduces to the ordinary non-Euclidean Fourier transform of Helgason for Ω=𝔻 (the unit disc). In both cases the proofs go via uniformization, and in (1) we obtain a Myrberg-like formula for the corresponding Green function. Finally, the latter formula as well as the eigenfunction expansion are worked out more explicitly in the simplest case of Ω an annulus, and a result is established concerning the convergence of the series ∑ _ω∈G (1-|ω0|²) ^s for G the covering group of the uniformization map of Ω and 0<s<1. Received: August 21, 2000?Published online: October 30, 2002 RID="*" ID="*"The first author was supported by GA AV CR grants no. A1019701 and A1019005.     

On the eigenfunction expansion of the Laplace–Beltrami operator in hyperbolic space

We describe the spectral projection of the Laplace–Beltrami operator in n-dimensional hyperbolic space by studying its resolvent as an analytic operator-valued function and applying the technique of contour integration. As a result an integral formula is established for the associated Legendre function     

A Note on Common Zeroes of Laplace–Beltrami Eigenfunctions

Let u+u=v+v= 0, where isthe Laplace–Beltrami operator on a compact connected smoothmanifold M and > 0. If H ¹(M) = 0then there exists pM such that u(p)=v(p) = 0 For homogeneous M,H ¹(M) 0 implies the existence of a pair u,v as above that has no common zero.     

A lower bound on the blow-up rate for the Davey–Stewartson system on the torus

We consider the hyperbolic–elliptic version of the Davey–Stewartson system with cubic nonlinearity posed on the two-dimensional torus. A natural setting for studying blow-up solutions for this equation takes place in H^s$H^s$, 1/2<s<1$1/2<s<1$. In this paper, we prove a lower bound on the blow-up rate for these regularities.     

Eigenfunctions of the Laplace–Beltrami Operator on Harmonic $$$$ Groups

We characterize some \(L^p\)-type eigenfunctions of the Laplace–Beltrami operator on harmonic \(NA\) groups corresponding to the eigenvalue \((\rho ^2-\beta ^2)\) for all \(\beta >0\).     

Representation of the Green’s function of the exterior Neumann problem for the Laplace operator

We represent the Green’s function of the classical Neumann problem for the exterior of the unit ball of arbitrary dimension. We show that the Green’s function can be expressed through elementary functions. The explicit form of the function is written out.     

A lower bound on the Chvátal-rank of Antiwebs

In [Holm, E., L. M. Torres and A. K. Wagler, On the Chvátal-rank of linear relaxations of the stable set polytope, International Transactions in Operational Research 17 (2010), pp. 827–849; Holm, E., L. M. Torres and A. K. Wagler, On the Chvátal-rank of Antiwebs, Electronic Notes in Discrete Mathematics 36 (2010), pp. 183–190] we study the Chvátal-rank of the edge constraint and the clique constraint stable set polytopes related to antiwebs. We present schemes for obtaining both upper and lower bounds. Moreover, we provide an algorithm to compute the exact values of the Chvátal-rank for all antiwebs with up to 5,000 nodes. Here we prove a lower bound as a closed formula and discuss some cases when this bound is tight.     

Spectral structure of the Neumann–Poincaré operator on tori

We address the question whether there is a three-dimensional bounded domain such that the Neumann–Poincaré operator defined on its boundary has infinitely many negative eigenvalues. It is proved in this paper that tori have such a property. It is done by decomposing the Neumann–Poincaré operator on tori into infinitely many self-adjoint compact operators on a Hilbert space defined on the circle using the toroidal coordinate system and the Fourier basis, and then by proving that the numerical range of infinitely many operators in the decomposition has both positive and negative values.     

The Landau–Kolmogorov problem for the Laplace operator on a ball

In this paper we solve the problem of maximizing the value of the Laplace operator at the origin for functions such that the second degree of the Laplace operator belongs to the space L_∞ on the unit ball of the Euclidean space. The problem is solved under restrictions on the uniform norm of a function and the L_∞-norm of the second degree of the Laplace operator of this function.     

The kernel of the bezoutian for operator Polynomials ∗

Based on two set partitions of the symmetric group S_n expansion theorems by diagonal elements for the permanent and the determinant are derived, for both the generic commuting and noncommuting cases. They are of the same type as the well-known Laplace expansions where either fixed rows or columns of a given matrix are chosen instead of diagonal elements.     

High-Order AFEM for the Laplace–Beltrami Operator: Convergence Rates

We present a new AFEM for the Laplace–Beltrami operator with arbitrary polynomial degree on parametric surfaces, which are globally \(W^1_\infty \) and piecewise in a suitable Besov class embedded in \(C^{1,\alpha }\) with \(\alpha \in (0,1]\). The idea is to have the surface sufficiently well resolved in \(W^1_\infty \) relative to the current resolution of the PDE in \(H^1\). This gives rise to a conditional contraction property of the PDE module. We present a suitable approximation class and discuss its relation to Besov regularity of the surface, solution, and forcing. We prove optimal convergence rates for AFEM which are dictated by the worst decay rate of the surface error in \(W^1_\infty \) and PDE error in \(H^1\).     

A remark on wave breaking for the Dullin–Gottwald–Holm equation

In this paper, a new sufficient condition to guarantee wave breaking for the Dullin–Gottwald–Holm equation is established, which is a local criterion and easy to check.     

A short proof of Gowers’ lower bound for the regularity lemma

A celebrated result of Gowers states that for every ?>0 there is a graph G such that every ?-regular partition of G (in the sense of Szemerédi’s regularity lemma) has order given by a tower of exponents of height polynomial in 1/?. In this note we give a new proof of this result that uses a construction and proof of correctness that are significantly simpler and shorter.