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Full Description
Integral geometry deals with the problem of determining functions by their integrals over given families of sets. These integrals de?ne the corresponding integraltransformandoneofthemainquestionsinintegralgeometryaskswhen this transform is injective. On the other hand, when we work with complex measures or forms, operators appear whose kernels are non-trivial but which describe important classes of functions. Most of the questions arising here relate, in one way or another, to the convolution equations. Some of the well known publications in this ?eld include the works by J. Radon, F. John, J. Delsarte, L. Zalcman, C. A. Berenstein, M. L. Agranovsky and recent monographs by L. H¨ ormander and S. Helgason. Until recently research in this area was carried out mostly using the technique of the Fourier transform and corresponding methods of complex analysis. In recent years the present author has worked out an essentially di?erent methodology based on the description of various function spaces in terms of - pansions in special functions, which has enabled him to establish best possible results in several well known problems.
Contents
1. Preliminaries.- 1 Sets and Mappings.- 2 Some Classes of Functions.- 3 Distributions.- 4 Some Special Functions.- 5 Some Results Related to Spherical Harmonics.- 6 Fourier Transform and Related Questions.- 7 Partial Differential Equations.- 8 Radon Transform Over Hyperplanes.- 9 Comments And Open Problems.- 2. Functions with zero integrals over balls of a fixed radius.- 1 Functions With Zero Averages Over Balls on Subsets of The Space ?n.- 2 Averages Over Balls on Hyperbolic Spaces.- 3 Functions With Zero Integrals Over Spherical Caps.- 4 Comments And Open Problems.- 3. Convolution equation on domains in ?n.- 1 One-Dimensional Case.- 2 General Solution Of Convolution Equation In Domains With Spherical Symmetry.- 3 Behavior of Solutions of Convolution Equation at Infinity.- 4 Systems Of Convolution Equations.- 5 Comments And Open Problems.- 4. Extremal versions of the Pompeiu problem.- 1 Sets With The Pompeiu Property.- 2 Functions With Vanishing Integrals Over Parallelepipeds.- 3 Polyhedra With Local Pompeiu Property.- 4 Functions with Vanishing Integrals over Ellipsoids.- 5 Other Sets With Local Pompeiu Property.- 6 The 'Three Squares' Problem And Related Questions.- 7 Injectivity Sets of the Pompeiu Transform.- 8 Comments and Open Problems.- 5. First applications and related questions.- 1 Injectivity Sets For Spherical Radon Transform.- 2 Some Questions Of Approximation Theory.- 3 Gap Theorems.- 4 Morera Type Theorems.- 5 Mean Value Characterization of Various Classes of Functions.- 6 Applications To Partial Differential Equations.- 7 Some Questions Of Measure Theory.- 8 Functions With Zero Integrals In Problems Of The Discrete Geometry.- 9 Comments And Open Problems.- Author Index.- Basic Notations.
