CatDat

Malcev

A category is Malcev when it has finite limits and every internal reflexive relation is an internal equivalence relation. That is, if $R \subseteq X^2$ is a subobject with $\Delta_X \subseteq R$, then $R$ is symmetric and transitive.

• Dual property: co-Malcev
• Related properties: finitely complete
• nLab Link

Relevant implications

• additive andfinitely complete implies Malcev
• co-Malcev andself-dual implies Malcev
• finitely complete andthin implies Malcev
• Malcev andpointed implies unital
• Malcev andself-dual implies co-Malcev
• Malcev implies finitely complete

Examples

There are 23 categories with this property.

• category of abelian groups
• category of abelian sheaves
• category of algebras
• category of commutative algebras
• category of commutative rings
• category of finite abelian groups
• category of finitely generated abelian groups
• category of free abelian groups
• category of groups
• category of left modules over a division ring
• category of left modules over a ring
• category of rings
• category of rngs
• category of vector spaces
• dual of the category of sets
• poset [0,1]
• poset of extended natural numbers
• proset of integers w.r.t. divisibility
• trivial category
• walking commutative square
• walking composable pair
• walking isomorphism
• walking morphism

Counterexamples

There are 42 categories without this property.

• category of Banach spaces with linear contractions
• category of combinatorial species
• category of commutative monoids
• category of fields
• category of finite orders
• category of finite sets
• category of finite sets and bijections
• category of finite sets and injections
• category of finite sets and surjections
• category of Hausdorff spaces
• 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 posets
• category of prosets
• category of schemes
• category of sets
• category of sets and relations
• category of sheaves
• category of simplicial sets
• category of small categories
• category of smooth manifolds
• category of topological spaces
• category of Z-functors
• delooping of a non-trivial finite group
• delooping of an infinite 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 of natural numbers
• poset of ordinal numbers
• walking fork
• walking parallel pair of morphisms
• walking span

Unknown

There are 0 categories for which the database has no information on whether they satisfy this property.

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