coextensive
A category is coextensive when it has finite products and for all objects the product functor is an equivalence of categories. The prototypical example is the category of commutative rings.
- Dual property: extensive
- Related properties: disjoint finite products, finite products, infinitary coextensive
Relevant implications
- coextensive andcomplete andlocally cocartesian coclosed implies infinitary coextensive
- coextensive andcoregular andmono-regular implies effective congruences andMalcev
- coextensive andeffective cocongruences implies epi-regular
- coextensive andfiltered colimits andinitial object implies cartesian filtered colimits
- coextensive andfinite coproducts implies codistributive
- coextensive andself-dual implies extensive
- coextensive implies disjoint finite products andstrict terminal object
- coextensive implies finite products
- disjoint finite products andlocally cocartesian coclosed implies coextensive
- extensive andself-dual implies coextensive
- infinitary coextensive implies coextensive
Examples
There are 5 categories with this property.
- category of commutative algebras
- category of commutative rings
- dual of the category of sets
- trivial category
- walking isomorphism
Counterexamples
There are 75 categories without this property.
- category of abelian groups
- category of abelian sheaves
- category of algebras
- category of Banach spaces with linear contractions
- category of combinatorial species
- category of commutative monoids
- category of compact Hausdorff spaces
- category of countable groups
- category of countable sets
- category of fields
- category of finite abelian groups
- category of finite groups
- category of finite ordered sets
- category of finite sets
- category of finite sets and bijections
- category of finite sets and injections
- category of finite sets and surjections
- category of finitely generated abelian groups
- category of free abelian groups
- category of groups
- category of Hausdorff spaces
- category of Jónsson-Tarski algebras
- category of left modules over a division ring
- category of left modules over a ring
- category of locally ringed spaces
- category of M-sets
- category of measurable spaces
- category of metric spaces with continuous maps
- category of metric spaces with non-expansive maps
- category of metric spaces with ∞ allowed
- category of monoids
- category of non-empty sets
- category of pairs of sets
- category of pointed sets
- category of pointed topological spaces
- category of posets
- category of prosets
- category of pseudo-metric spaces with non-expansive maps
- category of rings
- category of rngs
- category of schemes
- category of semigroups
- category of sets
- category of sets and relations
- category of sets with finite-to-one maps
- category of sheaves
- category of simplicial sets
- category of small categories
- category of smooth manifolds
- category of topological spaces
- category of torsion abelian groups
- category of torsion-free abelian groups
- category of vector spaces
- category of Z-functors
- delooping of a non-trivial finite group
- delooping of an infinite countable group
- delooping of the additive monoid of natural numbers
- delooping of the additive monoid of ordinal numbers
- discrete category on two objects
- empty category
- poset [0,1]
- poset of extended natural numbers
- poset of natural numbers
- poset of ordinal numbers
- proset of integers w.r.t. divisibility
- simplex category
- walking commutative square
- walking composable pair
- walking coreflexive pair
- walking fork
- walking idempotent
- walking morphism
- walking parallel pair
- walking span
- walking splitting
Unknown
There are 0 categories for which the database has no information on whether they satisfy this property.
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