منابع مشابه
A Characterization of Absolute Neighborhood Retracts
By an absolute neighborhood retract (ANR) I mean a separable metrizable space which is a neighborhood retract of every separable metrizable space which contains it and in which it is closed. This generalization of Borsuk's original definition was given by Kuratowski for the purpose of enlarging the class of absolute neighborhood retracts to include certain spaces which are not compact. The spac...
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Let G and H be two cographs. We show that the problem to determine whether H is a retract of G is NP-complete. We show that this problem is fixed-parameter tractable when parameterized by the size of H. When restricted to the class of threshold graphs or to the class of trivially perfect graphs, the problem becomes tractable in polynomial time. The problem is also soluble in linear time when on...
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A non-empty set X of a carrier A of an algebra A is called Q-independent if the equality of two term functions f and g of the algebra A on any finite system of elements a1, a2, . . . , an of X implies f(p(a1), p(a2), . . . , p(an)) = g(p(a1), p(a2), . . . , p(an)) for any mapping p ∈ Q. An algebra B is a retract of A if B is the image of a retraction (i.e. of an idempotent endomorphism of B). W...
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This paper solves the problem of determining the number of cells in an invertible three neighborhood null-boundary uniform cellular automaton (CA) by using its rule vector graph (RVG). The RVG represents an efficient data structure designed to characterize CA evolution and is derived out of its rule vector (RV). The concept of a horizontal rule vector subgraph (HRVS) is introduced to formulate ...
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We use rigorous numerical techniques to compute a lower bound for the exponent of expansivity outside a neighborhood of the critical point for thousands of intervals of parameter values in the quadratic family. We first compute a radius of the critical neighborhood outside which the map is uniformly expanding. This radius is taken as small as possible, yet large enough for our numerical procedu...
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ژورنال
عنوان ژورنال: Pacific Journal of Mathematics
سال: 1961
ISSN: 0030-8730,0030-8730
DOI: 10.2140/pjm.1961.11.609