منابع مشابه
Cofibrations and Bicofibrations
The paper deals with the correlated concepts of cofibration and bicofibration in C∗-algebra theory. We study cofibrations of C∗-algebras introduced by Claude Schochet in [9] (see also [7]). Cofibrations are characterized by means of the mapping cylinder C∗-algebras. We also define and analyse the notion of bicofibration for C∗-algebras based on the topological model from [8] (see also [5]). As ...
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Suppose /: X —• Y is a map of 1-connected spaces. In the "stable" range, roughly where the connectivity of Y exceeds the homology, or homotopy, dimension of X, it is well known that / can be extended as a cofibration C — X — Y, or respectively a fibration X — Y — B. A criterion is given for the existence of such extensions in a less restrictive "metastable" range. A main result is that if / is ...
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One of the most interesting aspects in the theory of cellular automata is the study of different types of nilpotency, that is, different ways in which a cellular automaton can force a particular symbol (usually called 0) to appear frequently in all its spacetime diagrams. The simplest such notion, called simply ‘nilpotency’, is that the cellular automaton c maps every configuration to a uniform...
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We consider categories of coalgebras as (co)-fibred over a base category of parameters and analyse categorical constructions in the total category of deterministic and non-deterministic coalgebras.
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Conditions are given for a class 2 nilpotent group to have no central extensions of class 3. This is related to Betti numbers and to the problem of representing a class 2 nilpotent group as the fundamental group of a smooth projective variety. Surveys of the work on the characterization of the fundamental groups of smooth projective varieties and Kähler manifolds (see [1],[3], [9]) indicate tha...
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ژورنال
عنوان ژورنال: Transactions of the American Mathematical Society
سال: 1981
ISSN: 0002-9947
DOI: 10.1090/s0002-9947-1981-0621979-1