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基本説明
Introduces the mathematical background of the subject, beginning with curves and surfaces, going on with convex subsets, smooth submanifolds.
Full Description
The central object of this book is the measure of geometric quantities describing N a subset of the Euclidean space (E ,), endowed with its standard scalar product. Let us state precisely what we mean by a geometric quantity. Consider a subset N S of points of the N-dimensional Euclidean space E , endowed with its standard N scalar product. LetG be the group of rigid motions of E . We say that a 0 quantity Q(S) associated toS is geometric with respect toG if the corresponding 0 quantity Q[g(S)] associated to g(S) equals Q(S), for all g?G . For instance, the 0 diameter ofS and the area of the convex hull ofS are quantities geometric with respect toG . But the distance from the origin O to the closest point ofS is not, 0 since it is not invariant under translations ofS. It is important to point out that the property of being geometric depends on the chosen group. For instance, ifG is the 1 N group of projective transformations of E , then the property ofS being a circle is geometric forG but not forG , while the property of being a conic or a straight 0 1 line is geometric for bothG andG . This point of view may be generalized to any 0 1 subsetS of any vector space E endowed with a groupG acting on it.
Contents
Motivations.- Motivation: Curves.- Motivation: Surfaces.- Background: Metrics and Measures.- Distance and Projection.- Elements of Measure Theory.- Background: Polyhedra and Convex Subsets.- Polyhedra.- Convex Subsets.- Background: Classical Tools in Differential Geometry.- Differential Forms and Densities on EN.- Measures on Manifolds.- Background on Riemannian Geometry.- Riemannian Submanifolds.- Currents.- On Volume.- Approximation of the Volume.- Approximation of the Length of Curves.- Approximation of the Area of Surfaces.- The Steiner Formula.- The Steiner Formula for Convex Subsets.- Tubes Formula.- Subsets of Positive Reach.- The Theory of Normal Cycles.- Invariant Forms.- The Normal Cycle.- Curvature Measures of Geometric Sets.- Second Fundamental Measure.- Applications to Curves and Surfaces.- Curvature Measures in E2.- Curvature Measures in E3.- Approximation of the Curvature of Curves.- Approximation of the Curvatures of Surfaces.- On Restricted Delaunay Triangulations.
