A Survey of Graphical Languages for Monoidal Categories
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A Convenient Category for Higher-Order Probability Theory
A Convenient Category for Higher-Order Probability Theory Chris Heunen Ohad Kammar Sam Staton Hongseok Yang University of Edinburgh, UK University of Oxford, UK University of Oxford, UK University of Oxford, UK Abstract—Higher-order probabilistic programming languages 1 (defquery Bayesian-linear-regression allow programmers to write sophisticated models in machine 2 let let sample normal learning and statistics in a succinct and structured way, but step ( [f ( [s ( ( 0.0 3.0)) 3 sample normal outside the standard measure-theoretic formalization of proba- b ( ( 0.0 3.0))] 4 fn + * bility theory. Programs may use both higher-order functions and ( [x] ( ( s x) b)))] continuous distributions, or even define a probability distribution 5 (observe (normal (f 1.0) 0.5) 2.5) on functions. But standard probability theory does not handle 6 (observe (normal (f 2.0) 0.5) 3.8) higher-order functions well: the category of measurable spaces 7 (observe (normal (f 3.0) 0.5) 4.5) is not cartesian closed. 8 (observe (normal (f 4.0) 0.5) 6.2) Here we introduce quasi-Borel spaces. We show that these 9 (observe (normal (f 5.0) 0.5) 8.0) spaces: form a new formalization of probability theory replacing 10 (predict :f f))) measurable spaces; form a cartesian closed category and so support higher-order functions; form a well-pointed category and so support good proof principles for equational reasoning; and support continuous probability distributions. We demonstrate the use of quasi-Borel spaces for higher-order functions and proba- bility by: showing that a well-known construction of probability theory involving random functions gains a cleaner expression; and generalizing de Finetti’s theorem, that is a crucial theorem in probability theory, to quasi-Borel spaces. -
Bialgebras in Rel
CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector Electronic Notes in Theoretical Computer Science 265 (2010) 337–350 www.elsevier.com/locate/entcs Bialgebras in Rel Masahito Hasegawa1,2 Research Institute for Mathematical Sciences Kyoto University Kyoto, Japan Abstract We study bialgebras in the compact closed category Rel of sets and binary relations. We show that various monoidal categories with extra structure arise as the categories of (co)modules of bialgebras in Rel.In particular, for any group G we derive a ribbon category of crossed G-sets as the category of modules of a Hopf algebra in Rel which is obtained by the quantum double construction. This category of crossed G-sets serves as a model of the braided variant of propositional linear logic. Keywords: monoidal categories, bialgebras and Hopf algebras, linear logic 1 Introduction For last two decades it has been shown that there are plenty of important exam- ples of traced monoidal categories [21] and ribbon categories (tortile monoidal cat- egories) [32,33] in mathematics and theoretical computer science. In mathematics, most interesting ribbon categories are those of representations of quantum groups (quasi-triangular Hopf algebras)[9,23] in the category of finite-dimensional vector spaces. In many of them, we have non-symmetric braidings [20]: in terms of the graphical presentation [19,31], the braid c = is distinguished from its inverse c−1 = , and this is the key property for providing non-trivial invariants (or de- notational semantics) of knots, tangles and so on [12,23,33,35] as well as solutions of the quantum Yang-Baxter equation [9,23]. -
Reasoning About Meaning in Natural Language with Compact Closed Categories and Frobenius Algebras ∗
Reasoning about Meaning in Natural Language with Compact Closed Categories and Frobenius Algebras ∗ Authors: Dimitri Kartsaklis, Mehrnoosh Sadrzadeh, Stephen Pulman, Bob Coecke y Affiliation: Department of Computer Science, University of Oxford Address: Wolfson Building, Parks Road, Oxford, OX1 3QD Emails: [email protected] Abstract Compact closed categories have found applications in modeling quantum information pro- tocols by Abramsky-Coecke. They also provide semantics for Lambek's pregroup algebras, applied to formalizing the grammatical structure of natural language, and are implicit in a distributional model of word meaning based on vector spaces. Specifically, in previous work Coecke-Clark-Sadrzadeh used the product category of pregroups with vector spaces and provided a distributional model of meaning for sentences. We recast this theory in terms of strongly monoidal functors and advance it via Frobenius algebras over vector spaces. The former are used to formalize topological quantum field theories by Atiyah and Baez-Dolan, and the latter are used to model classical data in quantum protocols by Coecke-Pavlovic- Vicary. The Frobenius algebras enable us to work in a single space in which meanings of words, phrases, and sentences of any structure live. Hence we can compare meanings of different language constructs and enhance the applicability of the theory. We report on experimental results on a number of language tasks and verify the theoretical predictions. 1 Introduction Compact closed categories were first introduced by Kelly [21] in early 1970's. Some thirty years later they found applications in quantum mechanics [1], whereby the vector space foundations of quantum mechanics were recasted in a higher order language and quantum protocols such as teleportation found succinct conceptual proofs. -
Basic Category Theory and Topos Theory
Basic Category Theory and Topos Theory Jaap van Oosten Jaap van Oosten Department of Mathematics Utrecht University The Netherlands Revised, February 2016 Contents 1 Categories and Functors 1 1.1 Definitions and examples . 1 1.2 Some special objects and arrows . 5 2 Natural transformations 8 2.1 The Yoneda lemma . 8 2.2 Examples of natural transformations . 11 2.3 Equivalence of categories; an example . 13 3 (Co)cones and (Co)limits 16 3.1 Limits . 16 3.2 Limits by products and equalizers . 23 3.3 Complete Categories . 24 3.4 Colimits . 25 4 A little piece of categorical logic 28 4.1 Regular categories and subobjects . 28 4.2 The logic of regular categories . 34 4.3 The language L(C) and theory T (C) associated to a regular cat- egory C ................................ 39 4.4 The category C(T ) associated to a theory T : Completeness Theorem 41 4.5 Example of a regular category . 44 5 Adjunctions 47 5.1 Adjoint functors . 47 5.2 Expressing (co)completeness by existence of adjoints; preserva- tion of (co)limits by adjoint functors . 52 6 Monads and Algebras 56 6.1 Algebras for a monad . 57 6.2 T -Algebras at least as complete as D . 61 6.3 The Kleisli category of a monad . 62 7 Cartesian closed categories and the λ-calculus 64 7.1 Cartesian closed categories (ccc's); examples and basic facts . 64 7.2 Typed λ-calculus and cartesian closed categories . 68 7.3 Representation of primitive recursive functions in ccc's with nat- ural numbers object . -
Categories of Quantum and Classical Channels (Extended Abstract)
Categories of Quantum and Classical Channels (extended abstract) Bob Coecke∗ Chris Heunen† Aleks Kissinger∗ University of Oxford, Department of Computer Science fcoecke,heunen,[email protected] We introduce the CP*–construction on a dagger compact closed category as a generalisation of Selinger’s CPM–construction. While the latter takes a dagger compact closed category and forms its category of “abstract matrix algebras” and completely positive maps, the CP*–construction forms its category of “abstract C*-algebras” and completely positive maps. This analogy is justified by the case of finite-dimensional Hilbert spaces, where the CP*–construction yields the category of finite-dimensional C*-algebras and completely positive maps. The CP*–construction fully embeds Selinger’s CPM–construction in such a way that the objects in the image of the embedding can be thought of as “purely quantum” state spaces. It also embeds the category of classical stochastic maps, whose image consists of “purely classical” state spaces. By allowing classical and quantum data to coexist, this provides elegant abstract notions of preparation, measurement, and more general quantum channels. 1 Introduction One of the motivations driving categorical treatments of quantum mechanics is to place classical and quantum systems on an equal footing in a single category, so that one can study their interactions. The main idea of categorical quantum mechanics [1] is to fix a category (usually dagger compact) whose ob- jects are thought of as state spaces and whose morphisms are evolutions. There are two main variations. • “Dirac style”: Objects form pure state spaces, and isometric morphisms form pure state evolutions. -
SHORT INTRODUCTION to ENRICHED CATEGORIES FRANCIS BORCEUX and ISAR STUBBE Département De Mathématique, Université Catholique
SHORT INTRODUCTION TO ENRICHED CATEGORIES FRANCIS BORCEUX and ISAR STUBBE Departement de Mathematique, Universite Catholique de Louvain, 2 Ch. du Cyclotron, B-1348 Louvain-la-Neuve, Belgium. e-mail: [email protected] — [email protected] This text aims to be a short introduction to some of the basic notions in ordinary and enriched category theory. With reasonable detail but always in a compact fashion, we have brought together in the rst part of this paper the denitions and basic properties of such notions as limit and colimit constructions in a category, adjoint functors between categories, equivalences and monads. In the second part we pass on to enriched category theory: it is explained how one can “replace” the category of sets and mappings, which plays a crucial role in ordinary category theory, by a more general symmetric monoidal closed category, and how most results of ordinary category theory can be translated to this more general setting. For a lack of space we had to omit detailed proofs, but instead we have included lots of examples which we hope will be helpful. In any case, the interested reader will nd his way to the references, given at the end of the paper. 1. Ordinary categories When working with vector spaces over a eld K, one proves such theorems as: for all vector spaces there exists a base; every vector space V is canonically included in its bidual V ; every linear map between nite dimensional based vector spaces can be represented as a matrix; and so on. But where do the universal quantiers take their value? What precisely does “canonical” mean? How can we formally “compare” vector spaces with matrices? What is so special about vector spaces that they can be based? An answer to these questions, and many more, can be formulated in a very precise way using the language of category theory. -
On the Completeness of the Traced Monoidal Category Axioms in (Rel,+)∗
Acta Cybernetica 23 (2017) 327–347. On the Completeness of the Traced Monoidal Category Axioms in (Rel,+)∗ Mikl´os Barthaa To the memory of my friend and former colleague Zolt´an Esik´ Abstract It is shown that the traced monoidal category of finite sets and relations with coproduct as tensor is complete for the extension of the traced sym- metric monoidal axioms by two simple axioms, which capture the additive nature of trace in this category. The result is derived from a theorem saying that already the structure of finite partial injections as a traced monoidal category is complete for the given axioms. In practical terms this means that if two biaccessible flowchart schemes are not isomorphic, then there exists an interpretation of the schemes by partial injections which distinguishes them. Keywords: monoidal categories, trace, iteration, feedback, identities in cat- egories, equational completeness 1 Introduction It was in March, 2012 that Zolt´an visited me at the Memorial University in St. John’s, Newfoundland. I thought we would find out a research topic together, but he arrived with a specific problem in mind. He knew about the result found by Hasegawa, Hofmann, and Plotkin [12] a few years earlier on the completeness of the category of finite dimensional vector spaces for the traced monoidal category axioms, and wanted to see if there is a similar completeness statement true for the matrix iteration theory of finite sets and relations as a traced monoidal category. Unfortunately, during the short time we spent together, we could not find the solu- tion, and after he had left I started to work on some other problems. -
On Closed Categories of Functors
ON CLOSED CATEGORIES OF FUNCTORS Brian Day Received November 7, 19~9 The purpose of the present paper is to develop in further detail the remarks, concerning the relationship of Kan functor extensions to closed structures on functor categories, made in "Enriched functor categories" | 1] §9. It is assumed that the reader is familiar with the basic results of closed category theory, including the representation theorem. Apart from some minor changes mentioned below, the terminology and notation employed are those of |i], |3], and |5]. Terminology A closed category V in the sense of Eilenberg and Kelly |B| will be called a normalised closed category, V: V o ÷ En6 being the normalisation. Throughout this paper V is taken to be a fixed normalised symmetric monoidal closed category (Vo, @, I, r, £, a, c, V, |-,-|, p) with V ° admitting all small limits (inverse limits) and colimits (direct limits). It is further supposed that if the limit or colimit in ~o of a functor (with possibly large domain) exists then a definite choice has been made of it. In short, we place on V those hypotheses which both allow it to replace the cartesian closed category of (small) sets Ens as a ground category and are satisfied by most "natural" closed categories. As in [i], an end in B of a V-functor T: A°P@A ÷ B is a Y-natural family mA: K ÷ T(AA) of morphisms in B o with the property that the family B(1,mA): B(BK) ÷ B(B,T(AA)) in V o is -2- universally V-natural in A for each B 6 B; then an end in V turns out to be simply a family sA: K ~ T(AA) of morphisms in V o which is universally V-natural in A. -
Note on Monoidal Localisation
BULL. AUSTRAL. MATH. SOC. '8D05« I8DI0' I8DI5 VOL. 8 (1973), 1-16. Note on monoidal localisation Brian Day If a class Z of morphisms in a monoidal category A is closed under tensoring with the objects of A then the category- obtained by inverting the morphisms in Z is monoidal. We note the immediate properties of this induced structure. The main application describes monoidal completions in terms of the ordinary category completions introduced by Applegate and Tierney. This application in turn suggests a "change-of- universe" procedure for category theory based on a given monoidal closed category. Several features of this procedure are discussed. 0. Introduction The first step in this article is to apply a reflection theorem ([5], Theorem 2.1) for closed categories to the convolution structure of closed functor categories described in [3]. This combination is used to discuss monoidal localisation in the following sense. If a class Z of morphisms in a symmetric monoidal category 8 has the property that e € Z implies 1D ® e € Z for all objects B € B then the category 8, of fractions of 8 with respect to Z (as constructed in [fl]. Chapter l) is a monoidal category. Moreover, the projection functor P : 8 -* 8, then solves the corresponding universal problem in terms of monoidal functors; hence such a class Z is called monoidal. To each class Z of morphisms in a monoidal category 8 there corresponds a monoidal interior Z , namely the largest monoidal class Received 18 July 1972. The research here reported was supported in part by a grant from the National Science Foundation' of the USA. -
A Survey of Graphical Languages for Monoidal Categories
5 Traced categories 32 5.1 Righttracedcategories . 33 5.2 Planartracedcategories. 34 5.3 Sphericaltracedcategories . 35 A survey of graphical languages for monoidal 5.4 Spacialtracedcategories . 36 categories 5.5 Braidedtracedcategories . 36 5.6 Balancedtracedcategories . 39 5.7 Symmetrictracedcategories . 40 Peter Selinger 6 Products, coproducts, and biproducts 41 Dalhousie University 6.1 Products................................. 41 6.2 Coproducts ............................... 43 6.3 Biproducts................................ 44 Abstract 6.4 Traced product, coproduct, and biproduct categories . ........ 45 This article is intended as a reference guide to various notions of monoidal cat- 6.5 Uniformityandregulartrees . 47 egories and their associated string diagrams. It is hoped that this will be useful not 6.6 Cartesiancenter............................. 48 just to mathematicians, but also to physicists, computer scientists, and others who use diagrammatic reasoning. We have opted for a somewhat informal treatment of 7 Dagger categories 48 topological notions, and have omitted most proofs. Nevertheless, the exposition 7.1 Daggermonoidalcategories . 50 is sufficiently detailed to make it clear what is presently known, and to serve as 7.2 Otherprogressivedaggermonoidalnotions . ... 50 a starting place for more in-depth study. Where possible, we provide pointers to 7.3 Daggerpivotalcategories. 51 more rigorous treatments in the literature. Where we include results that have only 7.4 Otherdaggerpivotalnotions . 54 been proved in special cases, we indicate this in the form of caveats. 7.5 Daggertracedcategories . 55 7.6 Daggerbiproducts............................ 56 Contents 8 Bicategories 57 1 Introduction 2 9 Beyond a single tensor product 58 2 Categories 5 10 Summary 59 3 Monoidal categories 8 3.1 (Planar)monoidalcategories . 9 1 Introduction 3.2 Spacialmonoidalcategories . -
Locally Cartesian Closed Categories, Coalgebras, and Containers
U.U.D.M. Project Report 2013:5 Locally cartesian closed categories, coalgebras, and containers Tilo Wiklund Examensarbete i matematik, 15 hp Handledare: Erik Palmgren, Stockholms universitet Examinator: Vera Koponen Mars 2013 Department of Mathematics Uppsala University Contents 1 Algebras and Coalgebras 1 1.1 Morphisms .................................... 2 1.2 Initial and terminal structures ........................... 4 1.3 Functoriality .................................... 6 1.4 (Co)recursion ................................... 7 1.5 Building final coalgebras ............................. 9 2 Bundles 13 2.1 Sums and products ................................ 14 2.2 Exponentials, fibre-wise ............................. 18 2.3 Bundles, fibre-wise ................................ 19 2.4 Lifting functors .................................. 21 2.5 A choice theorem ................................. 22 3 Enriching bundles 25 3.1 Enriched categories ................................ 26 3.2 Underlying categories ............................... 29 3.3 Enriched functors ................................. 31 3.4 Convenient strengths ............................... 33 3.5 Natural transformations .............................. 41 4 Containers 45 4.1 Container functors ................................ 45 4.2 Natural transformations .............................. 47 4.3 Strengths, revisited ................................ 50 4.4 Using shapes ................................... 53 4.5 Final remarks ................................... 56 i Introduction -
Dagger Symmetric Monoidal Category
Tutorial on dagger categories Peter Selinger Dalhousie University Halifax, Canada FMCS 2018 1 Part I: Quantum Computing 2 Quantum computing: States α state of one qubit: = 0. • β ! 6 α β state of two qubits: . • γ δ ac a c ad separable: = . • b ! ⊗ d ! bc bd otherwise entangled. • 3 Notation 1 0 |0 = , |1 = . • i 0 ! i 1 ! |ij = |i |j etc. • i i⊗ i 4 Quantum computing: Operations unitary transformation • measurement • 5 Some standard unitary gates 0 1 0 −i 1 0 X = , Y = , Z = , 1 0 ! i 0 ! 0 −1 ! 1 1 1 1 0 1 0 H = , S = , T = , √2 1 −1 ! 0 i ! 0 √i ! 1 0 0 0 I 0 0 1 0 0 CNOT = = 0 X ! 0 0 0 1 0 0 1 0 6 Measurement α|0 + β|1 i i 0 1 |α|2 |β|2 α|0 β|1 i i 7 Mixed states A mixed state is a (classical) probability distribution on quantum states. Ad hoc notation: 1 α 1 α + ′ 2 β ! 2 β′ ! Note: A mixed state is a description of our knowledge of a state. An actual closed quantum system is always in a (possibly unknown) “pure” (= non-mixed) state. 8 Density matrices (von Neumann) α Represent the pure state v = C2 by the matrix β ! ∈ αα¯ αβ¯ 2 2 vv† = C × . βα¯ ββ¯ ! ∈ Represent the mixed state λ1 {v1} + ... + λn {vn} by λ1v1v1† + ... + λnvnvn† . This representation is not one-to-one, e.g. 1 1 1 0 1 1 0 1 0 0 .5 0 + = + = 2 0 ! 2 1 ! 2 0 0 ! 2 0 1 ! 0 .5 ! 1 1 1 1 1 1 1 .5 .5 1 .5 −.5 .5 0 + = + = 2 √2 1 ! 2 √2 −1 ! 2 .5 .5 ! 2 −.5 .5 ! 0 .5 ! But these two mixed states are indistinguishable.