Notions of topos

Ross Street*

*Corresponding author for this work

    Research output: Contribution to journalArticle

    12 Citations (Scopus)


    A Grothendieck topos has the property that its Yoneda embedding has a left-exact left adjoint. A category with the latter property is called lex-total. It is proved here that every lex-total category is equivalent to its category of canonical sheaves. An unpublished proof due to Peter Freyd is extended slightly to yield that a lex-total category, which has a set of objects of cardinality at most that of the universe such that each object in the category is a quotient of an object from that set, is necessarily a Grothendieck topos.

    Original languageEnglish
    Pages (from-to)199-208
    Number of pages10
    JournalBulletin of the Australian Mathematical Society
    Issue number2
    Publication statusPublished - 1981


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