Table of contents

The survey is devoted to the multidimensional generalization of the Riemann zeta function as a function of a positive integral argument.

A closed subspace of functions holomorphic in a domain of the -dimensional complex space is considered. It is assumed that the subspace is invariant with respect to the partial differentiation operators and admits spectral synthesis, that is, coincides with the closure of the linear span of the common root elements in it of the partial differentiation operators. Conditions under which the elements of the invariant subspace admit analytic continuation to a larger domain are studied. The geometry of this domain depends both on the original domain and on the existence of functions admitting special lower bounds in the annihilator submodule of the invariant subspace. The same problem is also considered for topological products of invariant subspaces. The results are applied to the analytic continuation of solutions of homogeneous convolution equations.

In this paper a new theory of generalized continued fractions is constructed and applied to numbers, multidimensional vectors belonging to a real space, and infinite-dimensional vectors with integral coordinates. The theory is based on a concept generalizing the procedure for constructing the classical continued fractions and substantially using ergodic theory. One of the versions of the theory is related to differential equations. In the finite-dimensional case the constructions thus introduced are used to solve problems posed by Weyl in analysis and number theory concerning estimates of trigonometric sums and of the remainder in the distribution law for the fractional parts of the values of a polynomial, and also the problem of characterizing algebraic and transcendental numbers with the use of generalized continued fractions. Infinite-dimensional generalized continued fractions are applied to estimate sums of Legendre symbols and to obtain new results in the classical problem of the distribution of quadratic residues and non-residues modulo a prime. In the course of constructing these continued fractions, an investigation is carried out of the ergodic properties of a class of infinite-dimensional dynamical systems which are also of independent interest.