CatDat

regular-quotient-trivial

A category is regular-quotient-trivial if every regular epimorphism is an isomorphism. Equivalently, the poset of regular quotients of any object is trivial. Or as another equivalent condition, if a parallel pair $f, g : X \rightrightarrows Y$ has a coequalizer, then $f = g$. This is not standard terminology. We have added it to the database since it clarifies the relationship between several related properties.

• Dual property: regular-subobject-trivial
• Related properties: quotient-trivial, thin

Relevant implications

• co-Malcev andregular quotient object classifier implies regular-quotient-trivial
• coequalizers andregular-quotient-trivial is equivalent to thin
• disjoint finite coproducts andregular-quotient-trivial implies trivial
• disjoint finite products andregular-quotient-trivial implies trivial
• left cancellative implies regular-quotient-trivial
• quotient-trivial is equivalent to epi-regular andregular-quotient-trivial
• regular-quotient-trivial andself-dual implies regular-subobject-trivial
• regular-subobject-trivial andself-dual implies regular-quotient-trivial

Examples

There are 24 categories with this property.

• category of fields
• category of finite sets and bijections
• category of finite sets and injections
• delooping of a non-trivial finite group
• delooping of an infinite countable group
• delooping of an infinite uncountable 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
• trivial category
• walking commutative square
• walking composable pair
• walking fork
• walking idempotent
• walking isomorphism
• walking morphism
• walking parallel pair
• walking span

Counterexamples

There are 64 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 algebras
• category of commutative monoids
• category of commutative rings
• category of compact Hausdorff spaces
• category of countable groups
• category of countable sets
• category of filtered vector spaces
• category of finite abelian groups
• category of finite groups
• category of finite ordered sets
• category of finite sets
• category of finite sets and surjections
• category of finite-dimensional vector spaces [countable field]
• category of finite-dimensional vector spaces [finite field]
• category of finite-dimensional vector spaces [uncountable field]
• 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 set functions and commutative squares
• category of sets
• category of sets and relations
• category of sets with a distinguished subset
• 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
• dual of the category of sets
• dual of the category of topological spaces
• simplex category
• walking coreflexive pair
• walking splitting

Unknown

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

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