Questions tagged [monads]
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255 questions
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Cyclic lists of multisets
I am wondering if it is appropriate to ask about having a specific algebra for an endofunctor computed. We all know about the multiset monad, and it's endofunctor $\mathcal{M}_S$, and some might know ...
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Are flasque sheaves exactly the retracts of "canonically" flasque sheaves?
Let $X$ be a topological space. Let $X^\delta$ denote the space whose elements are the points of $X$, and which is equipped with the discrete topology. There is a continuous map $i : X^\delta\to X$ ...
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A morphism of monads that doesn't preserve thunkability?
Recall that for a monad $(T,\eta,\mu)$ on a category $C$, the Kleisli category $C_T$ has as objects the objects of $C$ and as morphisms $C_T(x,y) = C(x,T y)$. A morphism $f\in C_T(x,y) = C(x,T y)$ is ...
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Quantum scattering experiments: C-modules, N-modules and their monads
I am working on a theory of particle physics where we use monads. I have a few conjectures that I need to check.
The category of $\mathbb{C}$-modules is monadic over set
The category of $\mathbb{N}$...
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Transformation from the Bag monad to the List monad
The bag monad, sometimes called the multiset monad or free commutative monoid monad is a functor on Set that takes a set to its set of bags. These bags are like strings written in the elements of the ...
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144
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Multiset or Bag monad on Finite-Dimensional Hilbert Spaces
Edit: I will be happy if someone can get me the Bag monad on a 2-category of groupoids, regardless of any reference to Hilbert Spaces. (It's a fire sale!!)
I am trying to create the quantum ...
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Is this Frobenius Monad left exact? Does it preserve equalizers?
In this paper we see a Frobenius Monad in example 5.2. Suppose we take Hilb as the underlying category. Is this functor left exact? Does it preserve equalizers?
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Free commutative monoid monad
Has the monad induced by the free commutative monoid functor already been studied anywhere? Does it have any particular properties (other than not being cartesian)?
I would prefer a reference on ...
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141
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Trying to construct the ultrafilter 2-monad on $\mathbf{Cat}$
By which I mean, following Bôrger's paper Coproducts and Ultrafilters, the terminal monad among those that preserve finite coproducts, if such a thing can be constructed.
So far, what I have is, ...
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A monad that unions sets
Suppose we have a monad that maps types of some kind to other types (see below) , and let types be sets. Let $\alpha, \beta$ be types, $\rightarrow$ denote a function between types, and let $a : \...
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Computing a factorization of a monad
Given a monad, $(M, \mu, \eta)$, where $M: C \rightarrow C$ for some category $C$, there is a category of factorizations, $F\cdot G = M$ where $F: X \rightarrow C$, $G: C \rightarrow X$. Though this ...
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Algebras for general transfors
Algebras for endofunctors bridge the gap between functors acting on a category and structures defined in it. An algebra for an endofunctor $F$ is instantiated by some morphism $Fa \to a$, and more ...
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tree derived from monad is itself a monad
I have constructed a functor from a monad that appears (based on computer experiments to test the monad laws) to also have monad properties but I am having trouble proving it.
Here is the idea: M[A] ...
- 11
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Regarding a difficulty in the Fakir article about associated idempotent triple
I just had post this question in SE: https://math.stackexchange.com/questions/518054/about-details-of-the-fakir-theorem-proof-associated-idempotent-triple but dont get any answer.
I understand that ...
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Kleisli adjunction of the distribution monad
Let $\langle D , \mu, \eta \rangle$ be the distribution monad on $Set$ and let $Kl(D)$ be the Kleisli category on the distribution monad. I am interested in the adjunction between $Kl(D)$ and $Set$, ...
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Internal commutative monoid gives commutative monad
Let $(C,\otimes,1)$ be a symmetric monoidal category. Let $(M,\mu,\eta)$ be an internal commutative monoid object.
The functor $X\mapsto M\otimes X$ has a canonical monad structure, with unit and ...
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288
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comparison between two monadic definitions for an operad
According to May, an operad $\mathcal{C}$ valued in sets is equivalent to a monad in Cat on the endofunctor $C\colon X\mapsto \coprod_i \mathcal{C}(i)\times X^i.$
According to Leinster, an operad is ...
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89
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Recognition theorem for a functor (bi)category or category of monads?
$\DeclareMathOperator\Mnd{Mnd}$I have a bicategory and want to recognize if it's equivalent to $\Mnd(X)$ the bicategory of monads in some other bicategory $X$. Is there a theorem which does this ...
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Monoidal categories with canonical left-strengths of monads
It is well-known that every monad on Set is left-strong and that left-strength on a Set-monad is unique.
Is there an abstract characterization of monoidal categories $C$ for which every monad on $C$ ...
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Bialgebras in 1/Kl(D)
$1/Kl(D)$ is the comma category of the one element set in the Kleisli category of the distribution monad. There is mention of it here. The objects are probability distributions called states and the ...
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139
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Monads for proof relevance in type theory
I am just getting started with homotopy type theory. After watching an introductory lecture, I was attracted to the concept of proof relevance. In my understanding, the core idea here is to elevate ...
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Beck's original formulation of the precise tripleability theorem. Reference when considering reflexive pairs?
Thanks to MO's user Varkor, we have access to Beck's original untitled manuscript where Beck first stated his precise tripleability theorem. Up to terminological isomorphism, the PTT as stated in p. 3 ...
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When is a container a monad?
The category of polynomial functors on Set is equivalent to the category of containers.
We have a prescription for when a container is a comonad.
There are a few other questions that come to mind. ...
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102
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Can application in untyped lambda calculus be seen as the uncurried unit of some monad?
Simply typed lambda calculus in one type variable in a Cartesian closed category $\mathbf{C}$ can be interpreted as a family of Cartesian closed functors (described below, do they have a name?) from ...
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90
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Separable monads do not induce separable monoids
Let us first recall the categorical notion of monad: if we have a category $\mathcal{C}$ then a monad on it consists in an endofunctor $\mathbb{A}\colon \mathcal{C}\rightarrow \mathcal{C}$ together ...
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124
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The S-module Ass is same as the composite of Com and Lie
It has been cited in several places (eg. https://arxiv.org/pdf/1912.05519.pdf) that the S-module Ass is isomorphic to the composite of the S-modules Com and Lie. Is there a reference which gives the ...
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Are pseudomonoids weak algebras for a 2-monad?
I would like to know if whether or not the pseudomonoids in an arbitrary monoidal 2-category are (equivalent to) the weak algebras for some 2-monad (I am thinking about the free monoidal category 2-...
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Conditions such that split coequalizers are a symmetric notion
Consider the notion of a split coequalizer (see the nLab for the definition). Note that the definition seems to be non-symmetric. Are there any conditions on the ambient category such that it becomes ...
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103
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When do objects in the image of a functor $G$ have a unique action as algebras over the codensity monad of $G$?
Let $G:\mathcal{B}\longrightarrow \mathcal{A}$ be some functor which admits a right Kan extension along itself, $(\operatorname{Ran}_G G, \eta:\operatorname{Ran}_G G \circ G \rightarrow G)$.
The ...
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Do these monads on Rel compose?
$Rel$ is the category of sets and relations.
The cyclic list monad, $\mathcal{Cy}=(Cy, \mu_c, \eta_c)$ is defined as follows:
$Cy : Rel \rightarrow Rel$,
such that, $Cy(X)$ is all cyclic lists on ...
- 1,313
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Distributive laws of strong and/or monoidal monads
It is well-known that a commutative strong monad is the same as a monoidal monad.
Is there a notion of distributive law for commutative strong monads which is equivalently a distributive law for ...
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221
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Existence of free functor to Banach spaces
Is there a "non-trivial" characterization of the concrete categories admitting and adjoint pair of functors $F \dashv G$ were $G$ is defined on the category sBan of separable Banach spaces and bounded ...
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101
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Composition of monads induces tensor product in the category of modules
I have recently asked a question about the composition of two monads, namely $\mathcal{M}_P = \mathcal{M}_C \cdot \mathcal{M}_C$. I am conjecturing that the cateogory of $\mathbb{C}$-Modules and the ...
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Schemes for conditional distributions (monads)
(Note: This is a heuristic question. I'm trying to work out if this idea makes sense. I don't have much background in this area, so apologies if I'm wide of the mark.)
Suppose you have a monad ...
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The multi-set monad and modules
I am trying to analyze the category of algebras for the finite free commutative monoid monad, aka the finite multiset monad. This monad is frequently described as having a multiplication that takes a ...
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Codensity monad preserves some colimit?
Let $j: A \to B$ be a functor.
When $j$ has a left adjoint $L$, the codensity monad $\text{Ran}_jj$ will coincide with the monad $jL$. Since a left adjoint preserves all colimits, it is easy to ...
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Does the 2 category of Groupoids Admit the Vector Space Monad?
We can see here in Jacob's 2013 paper, that he seems to state that a particular kind of multiset monad is actually a vector space monad.
3.2. Vector spaces. For a semiring S one can define the ...
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Domain Monad on Density Operators Using Spectral Order
The spectral order for density operators is given in this paper Coecke Martin 2010. I won't give the full definition here. Essentially, it allows for a partial order of density matrices that forms a ...
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(Co)Monads with a mixed distributive law on the 2-Category of Groupoids
I am looking for containers on the 2-Category of Groupoids. In particular, though, I would like my container to be both a monad and a comonad with a mixed distributive law. Can someone provide one ...
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Is Det-Stoch a factorization of the Giry Monad?
Stoch is the category of Measurable spaces and stochastic maps. It is the Klesli category of the Giry monad. Deterministic theories form a subcategory of Stoch. Specifically, the objects are just ...
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The domain monad
$\DeclareMathOperator\Set{\mathit{Set}}\DeclareMathOperator\Dom{\mathit{Dom}}\DeclareMathOperator\Hilb{\mathit{Hilb}}$Many different kinds of data structures can be captured as Monads. Lists and ...
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Monads associated to Higher Categories
By Koudenburg The paper (arXiv:[1511.04070])(https://arxiv.org/pdf/1511.04070) generalizes 2-monad associated to hyper virtual double category.
Another paper (arXiv:[1310.8279]) (https://arxiv.org/...
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Do "factoradic" lists form a finitary monad?
I'm trying to understand better what it means for a monad to be finitary. I know that Lawvere theories correspond to finitary monads, but I don't really understand the definition in terms of filtered ...
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What are the necessary requirements to make this composite monad rewrite work?
It is well known that if you want to take two monads and compose them and get a third monad, you need a distributive law. Let us suppose we have this. So, we have two monads
$$\mathcal{M}$$
And
$$\...
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It's there a way to take a composite monad and a monad map to create a map of the composite?
Let us suppose you start with two monads, $M_S = \langle S , \eta_S, \mu_S \rangle$ and $M_T = \langle T , \eta_T, \mu_T \rangle$ and suppose you have a distributive law, $\lambda: ST \rightarrow TS$ ...
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Substitution structure on pointed sets
$\def\Fin{\text{Fin}_*}
\def\Set{\text{Set}_*}
\def\dd{\mathop{\diamond_\land}}$
The present question is intimately related to another question.
Let $\Fin$ be the category of pointed sets.
The ...
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191
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What is the measures monad for FDHilb?
I am labouring under a particular assumption that, perhaps, needs to be corrected. I believe that FDHilb, the category of Finite Dimensional Hilbert spaces and general linear maps is a category of ...
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iterated loop spaces and configuration spaces [closed]
In the lecture notes by J.P. May, The geometry of iterated loop spaces, Chapter 5, formula (1), (2) and (10), a map
$$
\phi: Hom_T(X,\Omega Y)\to Hom_T(SX,Y)
$$
is defined. And a map
$$
\eta_n=\phi^{-...
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Are there cartesian closed monads that also preserve the closed structure of the CCC
When I look for cartesian closed monads, I only find monads where the endofunctor preserves the cartesian structure of a cartesian closed category
$$
\operatorname T\ (a \times b) = (\operatorname T\ ...
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Expressing a model transformation by using monads in the simply-typed lambda calculus
In https://link.springer.com/content/pdf/10.1007/s10670-019-00128-z.pdf , page 16, the following clause is given for a modal operator $\langle R_k \rangle$ (see definition 4.2 for the definition of a ...
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