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arXiv 1104.3542math.CT
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具体性语境下的Kan扩张

Kan Extensions in Context of Concreteness

Jan Pavlík

摘要:

本文包含两个领域的结果-Kan扩张和具体范畴的形式理论。对前一主题的贡献是基于扩展的概念Kan扩展的锥,我们证明了极限锥创建Kan扩展。后一个主题的重点是两个显着的家庭的具体范畴的任意范畴。Beck范畴是由仿射性质定义的,而新引入的l-代数范畴是由函子代数范畴的极限描述的。后一个家庭被证明是相当自然的。著名的Beck定理指出,一元范畴正是具有自由对象的Beck范畴。我们加强这一定理,削弱假设的存在自由对象,我们取代它的存在一些Kan扩展,即逐点余密度单子。此外,使用的结果Kan扩张的锥,我们表明,l-代数范畴,甚至更弱的假设适合。

英文摘要:

This paper contains results from two areas -- formal theory of Kan extensions and concrete categories. The contribution to the former topic is based on the extension of the concept of Kan extension to the cones and we prove that limiting cones create Kan extensions. The latter topic focuses on two significant families of concrete categories over an arbitrary category. Beck categories are defined by preservance properties while newly introduced l-algebraic categories are described by limits of categories of functor algebras. The latter family is shown to be rather natural. The well known Beck's theorem states that the monadic categories are precisely the Beck categories with free objects. We strengthen this theorem by weakening the assumptions of the existence of free objects and we replace it by existence of some Kan extensions, namely the pointwise codensity monads. Moreover, using the result on Kan extensions of cones we show that for l-algebraic categories even weaker assumption fits.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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