We investigate limits in the 2-category of strict algebras and lax morphisms for a 2-monad. This includes both the 2-category of monoidal categories and monoidal functors as well as the 2-category of monoidal categories and opomonoidal functors, among many other examples.

Motivated by algebraic structures appearing in Rational Conformal Field Theory we study a construction associating to an algebra in a monoidal category a commutative algebra (full centre) in the monoidal centre of the monoidal category. We establish Morita invariance of this construction by extending it to module categories. As an example we treat the case of group-theoretical categories.

Many homotopy-coherent algebraic structures can be described by Segal-type limit conditions determined an “algebraic pattern”, which we mean ?-category equipped with a factorization system and collection of “elementary” objects. Examples that occur as such “Segal O-spaces” for pattern O include ?-categories, (?,n)-categories, ?-operads (including symmetric, non-symmetric, cyclic, modular ones),...

The Dijkstra and Hoare monads have been introduced recently for capturing weakest precondition computations and computations with preand post-conditions, within the context of program verification, supported by a theorem prover. Here we give a more general description of such monads in a categorical setting. We first elaborate the recently developed view on program semantics in terms of a trian...

It is also possible to define monads in terms of two other operations, map : (D → E) → M(D) → M(E) and join : M(M(D))→M(D). This is often the approach taken in category theory, but the definitions are equivalent. We use the notation [σ] to denote unit(σ), and the notation f∗(m) to denote bind(f)(m). Monads figure heavily in the programming language Haskell, which uses monads as a way to introdu...

Monads are used heavily in Haskell for supporting computational effects, and the language offers excellent support for defining monadic computations. Unfortunately, defining a monad remains a difficult challenge. There are no libraries that a programmer can use to define a monad that is not a composition of existing monad transformers; therefore every such effort must start from scratch despite...

It was argued by Crans that it is too much to ask that the category of Gray-categories admit a well behaved monoidal biclosed structure. We make this precise by establishing undesirable properties that any such monoidal biclosed structure must have. In particular we show that there does not exist any tensor product making the model category of Gray-categories into a monoidal model category.

Abstract. This survey of categorical structures, occurring naturally in mathematics, physics and computer science, deals with monoidal categories; various structures in monoidal categories; free monoidal structures; Penrose string notation; 2-dimensional categorical structures; the simplex equations of field theory and statistical mechanics; higher-order categories and computads; the (v,d)-cube...

We consider a symmetric monoidal closed category V = (V ,⊗, I, [−,−]) together with a regular injective object Q such that the functor [−, Q] : V → V op is comonadic and prove that in such a category, as in the monoidal category of abelian groups, a morphism of commutative monoids is an effective descent morphism for modules if and only if it is a pure monomorphism. Examples of this kind of mon...

We introduce an axiomatic extension of Höhle’s Monoidal Logic called Semi–divisible Monoidal Logic, and prove that it is complete by showing that semi–divisibility is preserved in MacNeille completion. Moreover, we introduce Strong semi– divisible Monoidal Logic and conjecture that a predicate formula α is derivable in Strong Semi–divisible Monadic logic if, and only if its double negation ¬¬α ...