Monographs in Contemporary Mathematics – serie

Author S.A. Stepanov thoroughly investigates the current state of the theory of Diophantine equations and its related methods. Discussions focus on arithmetic, algebraic-geometric, and logical aspects of the problem. Designed for students as well as researchers, the book includes over 250 excercises accompanied by hints, instructions, and references. Written in a clear manner, this text does not require readers to have special knowledge of modern methods of algebraic geometry.

This monograph constructs correct extensions of extremal problems, including problems of multicriteria optimization as well as more general cone optimization problems. The author obtains common conditions of stability and asymptotic nonsensitivity of extremal problems under perturbation of a part of integral restrictions for finite and infinite systems of restrictions. Features include individual chapters on nonstandard approximation of finitely additive measures by indefinite integrals and constructions of attraction sets. Professor Chentsov illustrates abstract settings by providing examples of problems of impulse control, mathematical programming, and stochastic optimization.

Presenting a new approach to qualitative analysis of integrable geodesic flows based on the theory of topological classification of integrable Hamiltonian systems, this book applies this technique systematically to a wide class of integrable systems. The first part of the book provides an introduction to the qualitative theory of integrable Hamiltonian systems and their invariants (symplectic geometry, integrability, the topology of Liouville foliations, the orbital classification theory for integrable nondegenerate Hamiltonian systems with two degrees of freedom, obstructions to integrability, for example). In the second part, the class of integrable geodesic flows on two-dimensional surfaces is discussed both from the classical and contemporary point of view. The authors classify them up to different equivalence relations such as an isometry, the Liouville equivalence, the trajectory equivalence (smooth and continuous), and the geodesic equivalence. A new technique, which provides the possibility to classify integrable geodesic flows up to these kinds of equivalences, is presented together with applications.

Geodesic flows of Riemannian metrics on manifolds are one of the classical objects in geometry. A particular place among them is occupied by integrable geodesic flows. We consider them in the context of the general theory of integrable Hamiltonian systems, and in particular, from the viewpoint of a new topological classification theory, which was recently developed for integrable Hamiltonian systems with two degrees of freedom. As a result, we will see that such a new approach is very useful for a deeper understanding of the topology and geometry of integrable geodesic flows. The main object to be studied in our paper is the class of integrable geodesic flows on two-dimensional surfaces. There are many such flows on surfaces of small genus, in particular, on the sphere and torus. On the contrary, on surfaces of genus 9 > 1, no such flows exist in the analytical case. One of the most important and interesting problems consists in the classification of integrable flows up to different equivalence relations such as (1) an isometry, (2) the Liouville equivalence, (3) the trajectory equivalence (smooth and continuous), and (4) the geodesic equivalence. In recent years, a new technique was developed, which gives, in particular, a possibility to classify integrable geodesic flows up to these kinds of equivalences. This technique is presented in our paper, together with various applications. The first part of our book, namely, Chaps.

An important part of the theory of partial differential equations is the theory of boundary problems for elliptic equations and systems of equations. Among such problems those of greatest interest are the so-called non-Fredholm boundary prob­ lems, whose investigation reduces, as a rule, to the study of singular integral equa­ tions, where the Fredholm alternative is violated for these problems. Thanks to de­ velopments in the theory of one-dimensional singular integral equations [28, 29], boundary problems for elliptic equations with two independent variables have been completely studied at the present time [13, 29], which cannot be said about bound­ ary problems for elliptic equations with many independent variables. A number of important questions in this area have not yet been solved, since one does not have sufficiently general methods for investigating them. Among the boundary problems of great interest is the oblique derivative problem for harmonic functions, which can be formulated as follows: In a domain D with sufficiently smooth boundary r find a harmonic function u(X) which, on r, satisfies the condition n n ~ au ~ . . . :;. . ai (X) ax. = f (X), . . . :;. . [ai (X)]2 = 1, i=l t i=l where aI, . . . , an,fare sufficiently smooth functions defined on r. Obviously the left side of the boundary condition is the derivative of the function u(X) in the direction of the vector P(X) with components al (X), . . . , an(X).

The homology of analytic sheaves is a natural apparatus in the theory of duality on complex spaces. The corresponding apparatus in algebraic geometry was developed by Grothendieck in the fifties. In complex ana- lytic geometry the apparatus of homology was missing until recently, and in its stead the hypercohomology of complex sheaves (the hyper-Ext func- tors) and the Aleksandrov-Cech homology with coefficients in co- presheaves were used. The homology of analytic sheaves, sheaves of germs of homology and homology groups of analytic sheaves, were intro- duced and studied in the mid-seventies in a number of papers by the author. The main goal of this book is to give a systematic and detailed account of the homology theory of analytic sheaves and some of its applications to duality theory on complex spaces and to the theory of hyperfunctions. In order to read this book one must be acquainted with the foundations of ho- mological algebra and the theory of topological vector spaces. Only the most elementary concepts and results from the theory of functions of sev- eral complex variables are assumed to be known.The information needed about sheaves and complex spaces is recounted briefly at the beginning of the fIrst chapter. v. D. Golovin v CONTENTS Chapter 1. ANALYTIC SHEA YES ...1 1. Prelirriinary Information ...1 2. Injectivity Test...16 3. Local Duality ...24 4. Injective and Global Dimension ...36 5. Properties of Fine Sheaves ...46 Chapter 2. HOMOLOGY THEORY ..." .. 63 1. Sheaves of Germs of Homology...63 ...