|
The theory of accessible categories originates from the work of Grothendieck completed by 1969 (Grothendieck (1972)) and Gabriel-Ulmer (1971). It has been further developed in 1989 by Michael Makkai and Robert Paré, with motivation coming from model theory, a branch of mathematical logic.〔J. Rosicky ("On combinatorial model categories" ), ''Arxiv'', 16 August 2007. Retrieved on 19 January 2008.〕 Accessible categories have also applications in homotopy theory.〔〔J. Rosicky, Injectivity and accessible categories〕 Grothendieck also continued the development of the theory for homotopy-theoretic purposes in his (still partly unpublished) 1991 manuscript Les dérivateurs (Grothendieck (1991)). Some properties of accessible categories depend on the set universe in use, particularly on the cardinal properties.〔J. Adamek and J. Rosicky, Locally Presentable and Accessible Categories, Cambridge University Press 1994〕 ==Definition== Let be an infinite regular cardinal and let be a category. An object of is called -presentable if the Hom functor preserves -directed colimits. The category is called -accessible provided that : * has -directed colimits * has a set of -presentable objects such that every object of is a -directed colimit of objects of A category is called accessible if is -accessible for some infinite regular cardinal . A -presentable object is usually called finitely presentable, and an -accessible category is often called finitely accessible. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Accessible category」の詳細全文を読む スポンサード リンク
|