Computation of the eigenvalues of Fredholm–Stieltjes integral equations

The Rayleigh–Ritz and the inverse iteration methods are used in order to compute the eigenvalues of Fredholm–Stieltjes integral equations, i.e. Fredholm equations with respect to suitable Stieltjes-type measures. Some applications to the so-called ‘charged’ (in German ‘belastete’) integral equation, and particularly the problem of computing the eigenvalues of a string charged by a finite number of cursors are given.     

Jackson’s integral of the Hurwitz zeta function

We give a Jacksonq-integral analogue of Euler’s logarithmic sine integral established in 1769 from several points of view, specifically from the one relating to the Hurwitz zeta function. Partially supported by Grant-in-Aid for Exploratory Research No. 15654003. Partially supported by Grant-in-Aid for Scientific Research (B) No. 15340003. Partially supported by Grant-in-Aid for Scientific Research (B) No. 15340012.     

On the ε-optimal control of quasilinear integral equations

We consider an optimal control problem for the stochastic quasilinear integro-functional equation , with cost functional . Two controls are introduced: a program control and a feedback control, generated by the optimal control of the problem under consideration when=0. It is proved that both controls are-optimal for the original problem.Translated fromTeoriya Sluchaínykh Protsessov, Vol. 14, pp. 96–100, 1986.     

A property of the β-Cauchy-type integral with continuous density

  A theorem from the classical complex analysis proved by Davydov in 1949 is extended to the theory of solution of a special case of the Beltrami equation in the z-complex plane (i.e., null solutions of the differential operator ). It is proved that if γ is a rectifiable Jordan closed curve and f is a continuous complex-valued function on γ such that the integral

Deformation of integral sections in the Mordell–Weil group

Using deformation theory, we answer two questions of Shioda concerning the infinitesimal structure of the moduli space of integral sections in the Mordell–Weil group.

     

Singular integral equations — The convergence of the Nyström interpolant of the Gauss-Chebyshev method

Nyström's interpolation formula is applied to the numerical solution of singular integral equations. For the Gauss-Chebyshev method, it is shown that this approximation converges uniformly, provided that the kernel and the input functions possess a continuous derivative. Moreover, the error of the Nyström interpolant is bounded from above by the Gaussian quadrature errors and thus convergence is fast, especially for smooth functions. ForC input functions, a sharp upper bound for the error is obtained. Finally numerical examples are considered. It is found that the actual computational error agrees well with the theoretical derived bounds.This research has been partially supported by a grant from the Rutgers Research Council.     

Convergence of the method of orthogonal polynomials for approximate solution of integral equations of the first kind with Π-kernels

The method of orthogonal polynomials for approxiamte solution of integral equations of the first kind with -kernels is substantiated. The solvability of the corresponding algebraic systems is proved, and estimates for the rate of the convergence of approxiamte solutions to exact ones are established. The applicability of the method of orthogonal polynomials to approximate solution of integral equations of the second kind with -kernels is shown, as well as its high effectiveness in solving integral equations of the first kind with -kernels. Concrete -kernels, most often occurring in applications, are presented.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 2, pp. 223–229, February, 1991.     

On the convergence of the Lavrent’ev method for an integral equation of the first kind with involution

The convergence in the mean-square metric of the Lavrent’ev regularizationmethod for an integral equation with involution is established. The proof of the convergence is based on studying the behavior of the resolvent of a certain integro-differential equation related to the original equation.     

Jacob’s ladders and the almost exact asymptotic representation of the Hardy-Littlewood integral

In this paper we introduce a nonlinear integral equation such that the system of global solutions to this equation represents the class of a very narrow beam as T → ∞ (an analog of the laser beam) and this sheaf of solutions leads to an almost-exact representation of the Hardy-Littlewood integral (1918). The accuracy of our result is essentially better than the accuracy of related results of Balasubramanian, Heath-Brown, and Ivic.     

Improvement of a Sinc-collocation method for Fredholm integral equations of the second kind

A Sinc-collocation scheme for Fredholm integral equations of the second kind was proposed by Rashidinia–Zarebnia in 2005. In this paper, two improved versions of the Sinc-collocation scheme are presented. The first version is obtained by improving the scheme so that it becomes more practical, and natural from a theoretical view point. Then it is rigorously proved that the convergence rate of the modified scheme is exponential, as suggested in the literature. In the second version, the variable transformation employed in the original scheme, the “tanh transformation”, is replaced with the “double exponential transformation”. It is proved that the replacement improves the convergence rate drastically. Numerical examples which support the theoretical results are also given.     

A group theory derivation of the relativistic path integral and the “history-string” dynamics

We derive the Feynman path integral for relativistic elementary particles using group theory considerations. We apply an approach in which choosing a symmetry group (or semigroup) allows deriving the kinematics and dynamics of a particle including the state space and the propagator from it. The quantum properties of a particle appear from intertwining two representations of the symmetry (semi)group, one of which describes local properties of the particle and the other describes the particle as a whole. The path-integrallike dynamics appears when the symmetry semigroup has a structure similar to that of the relativistic analogue of the Galilei group (in which the Lorentz-invariant “proper time” plays the role of time) with translations replaced with the semigroup of trajectories (parameterized paths). The classical action in the weight functional of the path integral is defined by this semigroup up to couplings to gauge and/or gravitational fields. The obtained formalism is suitable for describing not only pointlike particles but also nonlocal objects of the “history-string” type, which, as previously shown, allow explaining quark confinement.     

One-parameter family of integrable solutions of a system of nonlinear integral equations of the Hammerstein–Volterra type in the supercritical case

We study a system of nonlinear integral equations of the Hammerstein–Volterra type on a half-line in the supercritical case. We show that this system has a one-parameter family of positive integrable bounded solutions. We describe the structure of each solution in this family. The monotone dependence of the solutions on the parameter is proved.     

A study of the convergence of and error estimation for the homotopy perturbation method for the Volterra–Fredholm integral equations

In this work the solution of the Volterra–Fredholm integral equations of the second kind is presented. The proposed method is based on the homotopy perturbation method, which consists in constructing the series whose sum is the solution of the problem considered. The problem of the convergence of the series constructed is formulated and a proof of the formulation is given in the work. Additionally, the estimation of the approximate solution errors obtained by taking the partial sums of the series is elaborated on.     

Some properties of Γ-limits of integral functionals

Summary We prove some integral representation theorems for the Γ limit in L¹ of sequences of the form dx in coercivity and bounded growth hypothesis which are optimal as it is checked with examples. These results are utilized to describe the L¹ lower semicontinuous envelope of a given functional. We consider also the stability of Γ limits with respect to obstacle type perturbations and prove the homogenization formulas in conditions more generals of those already considered by several authors. Entrata in Redazione il 10 gennaio 1978.     

Improving the accuracy of multiple integral evaluation by applying Romberg’s method

Romberg’s method, which is used to improve the accuracy of one-dimensional integral evaluation, is extended to multiple integrals if they are evaluated using the product of composite quadrature formulas. Under certain conditions, the coefficients of the Romberg formula are independent of the integral’s multiplicity, which makes it possible to use a simple evaluation algorithm developed for one-dimensional integrals. As examples, integrals of multiplicity two to six are evaluated by Romberg’s method and the results are compared with other methods.