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arXiv · 1107.4620

Injective objects and retracts of Fraïssé limits

Wieslaw Kubiś
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Abstract

We present a purely category-theoretic characterization of retracts of Fraïssé limits. For this aim, we consider a natural version of injectivity with respect to a pair of categories (a category and its subcategory). It turns out that retracts of Fraïssé limits are precisely the objects that are injective relatively to such a pair. One of the applications is a characterization of non-expansive retracts of Urysohn's universal metric space.

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Wieslaw Kubiś. 2012-10-22. Injective objects and retracts of Fraïssé limits. https://doi.org/10.1515/forum-2012-0081

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