Proper shape retracts
نویسندگان
چکیده
منابع مشابه
On Retracts, Absolute Retracts, and Folds in Cographs
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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The subgroup R of the group G has been termed a retract of the group G whenever there exists an idempotent endomorphism of G which maps G upon R. This definition is in strict analogy to the topological concept of retract. Thus one may be tempted to define absolute retracts in like similarity to topological usage. However, we shall prove in the course of the present note that the identity is the...
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ژورنال
عنوان ژورنال: Fundamenta Mathematicae
سال: 1975
ISSN: 0016-2736,1730-6329
DOI: 10.4064/fm-89-2-177-189