TAILIEUCHUNG - Báo cáo hóa học: " ROOTS OF MAPPINGS FROM MANIFOLDS"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: ROOTS OF MAPPINGS FROM MANIFOLDS | ROOTS OF MAPPINGS FROM MANIFOLDS ROBIN BROOKS Received 15 June 2004 Assume that f X Y is a proper map of a connected n-manifold X into a Haus-dorff connected locally path-connected and semilocally simply connected space Y and y0 G Y has a neighborhood homeomorphic to Euclidean n-space. The proper Nielsen number of f at y0 and the absolute degree of f at y0 are defined in this setting. The proper Nielsen number is shown to a lower bound on the number of roots at y0 among all maps properly homotopic to f and the absolute degree is shown to be a lower bound among maps properly homotopic to f and transverse to y0. When n 2 these bounds are shown to be sharp. An example of a map meeting these conditions is given in which in contrast to what is true when Y is a manifold Nielsen root classes of the map have different multiplicities and essentialities and the root Reidemeister number is strictly greater than the Nielsen root number even when the latter is nonzero. 1. Introduction Let f X Y be a map of topological spaces and y0 G Y .A point x G X such that f x y0 is called a root of f at y0. In Nielsen root theory by analogy with Nielsen fixed-point theory the roots of f are grouped into Nielsen classes a notion of essentiality is defined and the Nielsen root number is defined to be the number of essential root classes. The Nielsen root number is a homotopically invariant lower bound for the number of roots of f at y0. When X is noncompact it is often of more interest to restrict attention to proper maps and proper homotopies and define a proper Nielsen root number. We also consider the topological analog of the case where y0 is a regular value of f. In this analog f is said to be transverse to y0. The map f is transverse to y0 if it has a neighborhood that is evenly covered by f. For this purpose Hopf 7 introduced the notion of absolute degree which we redefine in Section 3 below . For maps of compact oriented manifolds the absolute degree is the same up to sign as the .

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