Arc-smoothness and contractibility in Whitney levels
نویسندگان
چکیده
منابع مشابه
A1-contractibility and topological contractibility
These notes are an extended transcript of two lectures given at the University of Ottawa during the workshop “Group actions, generalized cohomology theories, and affine algebraic geometry." The first lecture was a general introduction to A1-homotopy theory focusing on motivating the choice of definitions in the construction, together with a definition of A1-contractible spaces. The second lectu...
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It is shown that δ-connectedness is not a Whitney reversible property. This answers in the negative a question posed by Sam B. Nadler, Jr. in 1978. A topological property P is said to be: (a) a Whitney property provided that if a continuum X has property P, so does μ−1(t) for each Whitney map μ for C(X) and each t ∈ [0, μ(X)) ([6, p. 165]); (b) a Whitney reversible property provided that whenev...
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Contractibility and NP-completeness
For a fixed graph H, let H-CON denote the problem of determining whether a given graph is contractible to H. The complexity of H-CON is studied for H belonging to certain classes of graphs, together covering all connected graphs of order at most 4. In particular, H-CON is NP-complete if H is a connected triangle-free graph other than a star. For each connected graph H of order a t most 4 other ...
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ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 1990
ISSN: 0002-9939
DOI: 10.1090/s0002-9939-1990-1037210-2