18,889 research outputs found

    Products of straight spaces

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    A metric space X is straight if for each finite cover of X by closed sets, and for each real valued function f on X, if f is uniformly continuous on each set of the cover, then f is uniformly continuous on the whole of X. A locally connected space is straight if it is uniformly locally connected (ULC). It is easily seen that ULC spaces are stable under finite products. On the other hand the product of two straight spaces is not necessarily straight. We prove that the product X x Y of two metric spaces is straight if and only if both X and Y are straight and one of the following conditions holds: (a) both X and Y are precompact; (b) both X and Y are locally connected; (c) one of the spaces is both precompact and locally connected. In particular, when X satisfies (c), the product X x Z is straight for every straight space Z. Finally, we characterize when infinite products of metric spaces are ULC and we completely solve the problem of straightness of infinite products of ULC spaces.Comment: 21 page

    On locally 1-connectedness of quotient spaces and its applications to fundamental groups

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    Let XX be a locally 1-connected metric space and A1,A2,...,AnA_1,A_2,...,A_n be connected, locally path connected and compact pairwise disjoint subspaces of XX. In this paper, we show that the quotient space X/(A1,A2,...,An)X/(A_1,A_2,...,A_n) obtained from XX by collapsing each of the sets AiA_i's to a point, is also locally 1-connected. Moreover, we prove that the induced continuous homomorphism of quasitopological fundamental groups is surjective. Finally, we give some applications to find out some properties of the fundamental group of the quotient space X/(A1,A2,...,An)X/(A_1,A_2,...,A_n).Comment: 11 page
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