Limits and Colimits of Hopf Algebras
نویسنده
چکیده
It is shown that for any commutative unital ring R the category HopfR of R–Hopf algebras is locally presentable and a coreflective subcategory of the category BialgR of R–bialgebras, admitting cofree Hopf algebras over arbitrary R–algebras. The proofs are based on an explicit analysis of the construction of colimits of Hopf algebras, which generalizes an observation of Takeuchi. Essentially be a duality argument also the dual statement, namely that HopfR is closed in BialgR under limits, is shown to hold, provided that the ring R is von Neumann regular. It then follows that HopfR is reflective in BialgR and admits free Hopf algebras over arbitrary R–coalgebras, for any von Neumann regular ring R. Finally, Takeuchi’s free Hopf algebra construction is analysed and shown to be simply a composition of standard categorical constructions. By simple dualization also a construction of the Hopf coreflection is provided.
منابع مشابه
Universal Constructions for Hopf Algebras
The category of Hopf monoids over an arbitrary symmetric monoidal category as well as its subcategories of commutative and cocommutative objects respectively are studied, where attention is paid in particular to the following questions: (a) When are the canonical forgetful functors of these categories into the categories of monoids and comonoids respectively part of an adjunction? (b) When are ...
متن کاملSubcategories of topological algebras
In addition to exploring constructions and properties of limits and colimits in categories of topological algebras, we study special subcategories of topological algebras and their properties. In particular, under certain conditions, reflective subcategories when paired with topological structures give rise to reflective subcategories and epireflective subcategories give rise to epireflective s...
متن کاملA characterisation of algebraic exactness
An algebraically exact category is one that admits all of the limits and colimits which every variety of algebras possesses and every forgetful functor between varieties preserves, and which verifies the same interactions between these limits and colimits as hold in any variety. Such categories were studied by Adámek, Lawvere and Rosický: they characterised them as the categories with small lim...
متن کاملNOTES ON REGULAR MULTIPLIER HOPF ALGEBRAS
In this paper, we associate canonically a precyclic mod- ule to a regular multiplier Hopf algebra endowed with a group-like projection and a modular pair in involution satisfying certain con- dition
متن کامل