Comparison theorems for weak splittings of bounded operators

Summary Comparison theorems for weak splittings of bounded operators are presented. These theorems extend the classical comparison theorem for regular splittings of matrices by Varga, the less known result by Wonicki, and the recent results for regular and weak regular splittings of matrices by Neumann and Plemmons, Elsner, and Lanzkron, Rose and Szyld. The hypotheses of the theorems presented here are weaker and the theorems hold for general Banach spaces and rather general cones. Hypotheses are given which provide strict inequalities for the comparisons. It is also shown that the comparison theorem by Alefeld and Volkmann applies exclusively to monotone sequences of iterates and is not equivalent to the comparison of the spectral radius of the iteration operators.This work was supported by the National Science Foundation grants DMS-8807338 and INT-8918502     

Comparisons of regular splittings of matrices

Summary In this article, new comparison theorems for regular splittings of matrices are derived. In so doing, the initial results of Varga in 1960 on regular splittings of matrices, and the subsequent unpublished results of Wonicki in 1973 on regular splittings of matrices, will be seen to be special cases of these new comparison theorems.Dedicated to Fritz Bauer on the occasion of his 60th birthdayResearch supported in part by the Air Force Office of Scientific Research, and by the Department of Energy     

A note on comparison theorems for nonnegative matrices

Summary In a recent paper, [4], Csordas and Varga have unified and extended earlier theorems, of Varga in [10] and Wonicki in [11], on the comparison of the asymptotic rates of convergence of two iteration matrices induced by two regular splittings. The main purpose of this note is to show a connection between the Csordas-Varga paper and a paper by Beauwens, [1], in which a comparison theorem is developed for the asymptotic rate of convergence of two nonnegative iteration matrices induced by two splittings which are not necessarily regular. Monotonic norms already used in [1] play an important role in our work here.Research supported in part by NSF grant number DMS-8400879     

The first nonzero eigenvalue of Neumann problem on Riemannian manifolds

In this article, the author obtained some comparison theorems of the first nonzero Neumann eigenvalue on domains in nonpositively curved Riemannian manifolds. The author first gives a generalized Szegö-Weinberger theorem (Theorem 1). Then the first nonzero Neumann eigenvalues for geodesic balls on nonpositively curved Riemannian manifolds are compared (Theorem 2). Based on these results, a “monotonicity principle” for the Neumann eigenvalues is derived. Then the author proves a stability theorem of maximality of the first nonzero Neumann eigenvalue of a geodesic ball among those of all domains with the same volume.     

有界线性算子非负分裂的比较

本文研究有界线性算子非负分裂的比较,建立了若干比较定理,给出了保证两个迭代算子的谱半径间严格不等式成立的一些充分条件．这些结论蕴涵并推广了Ｍａｒｅｋ 和Ｓｚｙｌｄ［２］以及作者［４］的相应结果     

Regular splittings and the discrete Neumann problem

Summary Iterative methods are discussed for approximating a solution to a singular but consistent square linear systemAx=b. The methods are based upon splittingA=M–N withM nonsingular. Monotonicity and the concept of regular splittings, introduced by Varga, are used to determine some necessary and some sufficient conditions in order that the iterationx ⁱ⁺¹=M^–1Nxⁱ+M^–1b converge to a solution to the linear system. Finally, applications are given to solving the discrete Neumann problem by iteration which are based upon the inherent monotonicity in the formulation.This research was supported by the U. S. Army Research Office-Durham under contract no. DAHCO4 74 C 0019.     

Comparison theorems for a subclass of proper splittings of matrices

In this article, a convergence theorem and several comparison theorems are presented for a subclass of proper splittings of matrices introduced recently.     

关于有界线性算子非负分裂的比较定理

Marek和Szyld建立了有界线性算子非负分裂的比较定理.他们还提出了严格不等式成立的条件,但没有进行详细证明.本注记首先用几个反例说明那里的保证严格不等式成立的条件是不充分的,然后给出正确的关于严格不等式的比较定理.     

Exact convergence and divergence domains for the symmetric successive overrelaxation iterative (SSOR) method applied to H-matrices

In this paper, exact convergence and divergence domains for the SSOR iterative method, as applied to the class of H-matrices, are obtained. The theory of regular splittings and the recent results of Varga, Niethammer, and Cai are used as tools in establishing these convergence and divergence domains.     

Comparison theorems for splittings of matrices

Summary. This paper investigates the comparisons of asymptotic rates of convergence of two iteration matrices. On the basis of nonnegative matrix theory, comparisons between two nonnegative splittings and between two parallel multisplitting methods are derived. When the coefficient matrix A is Hermitian positive (semi)definite, comparison theorems about two P-regular splittings and two parallel multisplitting methods are proved. Received April 4, 1998 / Revised version received October 18, 1999 / Published online November 15, 2001     

Zur Konvergenz des Peaceman-Rachford-Verfahrens

Summary In this paper we prove some results concerning the convergence of the Peaceman-Rachford iterative method. The main result covers both the stationary and the instationary case. No use is made of the so called commutativity condition which often was used in the literature in the instationary case. In proving the results of this paper it is made use of the theory of regular splittings which was introduced by R.S. Varga. Finally it is demonstrated how the results can be applied to discrete versions of elliptic boundary value problems.     

On resonant Neumann problems

We consider semilinear Neumann problems at resonance and prove existence and multiplicity theorems. The existence theorems allow resonance with respect to any eigenvalue of the negative Neumann Laplacian. The multiplicity theorems concern problems resonant at 0 (the principal eigenvalue) or at the first nonzero eigenvalue. Our approach uses tools from critical point theory and from Morse theory.     

Regular splittings and monotone iteration functions

Summary In this paper we introduce the set of so-called monotone iteration functions (MI-functions) belonging to a given function. We prove necessary and sufficient conditions in order that a given MI-function is (in a precisely defined sense) at least as fast as a second one.Regular splittings of a function which were initially introduced for linear functions by R.S. Varga in 1960 are generating MI-functions in a natural manner.For linear functions every MI-function is generated by a regular splitting. For nonlinear functions, however, this is generally not the case.     

A Jacobi spectral collocation method for solving multi-dimensional nonlinear fractional sub-diffusion equations

Graf’s and Neumann’s addition theorems for Bessel functions have been widely used in acoustic and electromagnetic scattering problems, especially the fast multipole method for 2-D scattering problems. This paper studies the truncation errors of Graf’s and Neumann’s addition theorems and their linear combinations. Explicit bounds and convergence rates of the truncation errors are derived, and convergence calculated. The conclusions are tested by numerical experiments and show that the derived bounds for the truncation errors of the addition theorems are valid.     

M-矩阵线性互补问题模系多分裂迭代方法的收敛性

首先证明了M-矩阵的H-相容分裂都是正则分裂,反之不成立.这表明对于M-矩阵而言,其正则分裂包含H-相容分裂.然后针对系数矩阵为M-矩阵的线性互补问题,建立了两个收敛定理:一是模系多分裂迭代方法关于正则分裂的收敛定理;二是模系二级多分裂迭代方法关于外迭代为正则分裂和内迭代为弱正则分裂的收敛定理.     

On a generalisation of self-injective von Neumann regular rings

Apart from von Neumann regular rings, rings with infinite identities have not been studied in any detail. We take a first step in that direction by obtaining structure theorems for a class of self-injective rings with infinite identities. These extend the main structure theorems for self-injective von Neumann regular rings.

     

Durchmesserabschätzungen für die einheitskugel des sobolev-raumes

Theory of parabolic differential inequalities, flow-invariance of solutions and comparison theorems are discussed relative to a cone.

In this paper we investigate the theory of parabolic differential inequalities in arbitrary cones. After discussing the fundamental results concerning parabolic inequalities in cones, we prove a result on flow-invariance which is then used to obtain a comparison theorem. This comparison result is useful in deriving upper and lower bounds on solutions of parabolic differential equations in terms of the solutions of ordinary differential equations. We treat the Dirichlet problem in this paper since its theory follows the general pattern of ordinary differential equations and requires less restrictive assumptions. The treatment of Neumann problem, on the other hand, demands stronger smoothness assumptions and depends heavily on strong maximum principle. The study of the corresponding results relative to Neumann problem is discussed elsewhere.     

Convergence of nested classical iterative methods for linear systems

Summary Classical iterative methods for the solution of algebraic linear systems of equations proceed by solving at each step a simpler system of equations. When this system is itself solved by an (inner) iterative method, the global method is called a two-stage iterative method. If this process is repeated, then the resulting method is called a nested iterative method. We study the convergence of such methods and present conditions on the splittings corresponding to the iterative methods to guarantee convergence forany number of inner iterations. We also show that under the conditions presented, the spectral radii of the global iteration matrices decrease when the number of inner iterations increases. The proof uses a new comparison theorem for weak regular splittings. We extend our results to larger classes of iterative methods, which include iterative block Gauss-Seidel. We develop a theory for the concatenation of such iterative methods. This concatenation appears when different numbers of inner interations are performed at each outer step. We also analyze block methods, where different numbers of inner iterations are performed for different diagonal blocks.Dedicated to Richard S. Varga on the occasion of his sixtieth birthdayP.J. Lanzkron was supported by Exxon Foundation Educational grant 12663 and the UNISYS Corporation; D.J. Rose was supported by AT&T Bell Laboratories, the Microelectronic Center of North Carolina and the Office of Naval Research under contract number N00014-85-K-0487; D.B. Szyld was supported by the National Science Foundation grant DMS-8807338.     

Precise domains of convergence for the block SSOR method associated withp-cyclic matrices

We apply Rouché's theorem to the functional equation relating the eigenvalues of theblock symmetric successive overrelaxation (SSOR) matrix with those of the block Jacobi iteration matrix found by Varga, Niethammer, and Cai, in order to obtain precise domains of convergence for the block SSOR iteration method associated withp-cyclic matricesA, p3. The intersection of these domains, taken over all suchp's, is shown to coincide with the exact domain of convergence of thepoint SSOR iteration method associated withH-matricesA. The latter domain was essentially discovered by Neumaier and Varga, but was recently sharpened by Hadjidimos and Neumann.Research supported in part by NSF Grant DMS 870064.     

Multiple Solutions for Gradient Elliptic Systems with Nonsmooth Boundary Conditions

In this paper we prove the existence of at least three solutions of gradient elliptic systems with nonhomogeneous and nonsmooth Neumann boundary conditions. Our investigations complete the results of J. Fernandez Bonder, S. Martinez, J.D. Rossi (NoDEA Nonlinear Differential Equations Appl. 2007). We use a recent generalization of a three critical points theorem of B. Ricceri (Nonlinear Anal. 2008) for locally Lipschitz functionals given by A. Kristály, W. Marzantowicz, Cs. Varga (J. Global Optim. 2010).