Author:
(1) Thierry Boy de la Tour, Univ. Grenoble Alpes, CNRS, Grenoble INP, LIG 38000 Grenoble, France. Author: Author: (1) Thierry Boy de la Tour, Univ. Grenoble Alpes, CNRS, Grenoble INP, LIG 38000 Grenoble, France. Table of Links Abstract and 1 Introduction Abstract and 1 Introduction 2 Basic Definitions and Notations 2.1 Sets 2.1 Sets 2.2 Sequences 2.2 Sequences 2.3 Signatures and Algebras and 2.4 Categories 2.3 Signatures and Algebras and 2.4 Categories 3 Monographs and their Morphisms 3 Monographs and their Morphisms 4 Limits and Colimits 4 Limits and Colimits 5 Drawing Monographs 5 Drawing Monographs 6 Graph Structures and Typed Monographs 6 Graph Structures and Typed Monographs 7 Submonographs and Partial Morphisms 7 Submonographs and Partial Morphisms 8 Algebraic Transformations of Monographs 8 Algebraic Transformations of Monographs 9 Attributed Typed Monographs 9 Attributed Typed Monographs 10 Conclusion and References 10 Conclusion and References 4 Limits and Colimits The colimits of monographs follow the standard constructions of colimits in Sets and Graphs. Sets Graphs Theorem 4.4. The categories of Definition 3.5 are finitely co-complete. Theorem 4.4. The categories of Definition 3.5 are finitely co-complete. We next investigate the limits in categories of monographs. Products of monographs are more difficult to build than products of graphs. This is due to the fact that edges of identical length may be adjacent to edges of different lengths. We therefore see that E (A x B) is only a subset of EA x EB. Lemma 4.6. Every pair of parallel morphisms f, g : A → B has an equalizer (E, e) eq such that E is finite whenever A is finite. Lemma 4.6. Every pair of parallel morphisms f, g : A → B has an equalizer (E, e) eq such that E is finite whenever A is finite. Corollary 4.7. The monomorphisms in Monogr are the injective morphisms. Corollary 4.7. The monomorphisms in Monogr are the injective morphisms. A well-known consequence of Lemmas 4.5 and 4.6 is that all non-empty finite diagrams in Monogr have limits. Since a limit of O-monographs (resp. standard monographs) is an O-monograph (resp. standard), this holds for all categories of Definition 3.5. In particular they all have pullbacks. We shall now investigate the limits of the empty diagram in these categories, i.e., their possible terminal objects. Definition 4.8. For any set of ordinals O, let Definition 4.8. For any set of ordinals O, let Lemma 4.11. Monogr, SMonogr and FMonogr have no terminal object. Lemma 4.11. Monogr, SMonogr and FMonogr have no terminal object. Since terminal objects are limits of empty diagrams obviously these categories are not finitely complete. Theorem 4.12. O-SMonogr is finitely complete for every set of ordinals O. The categories Monogr, SMonogr and FMonogr are not finitely complete. Theorem 4.12. O SMonogr is finitely complete for every set of ordinals O. The categories Monogr SMonogr and FMonogr are not finitely complete. Proof. By Lemmas 4.5, 4.6, 4.9 and 4.11. Proof The category Graphs is also known to be adhesive, a property of pushouts and pullbacks that has important consequences on algebraic transformations (see [8]) and that we shall therefore investigate. Graphs Definition 4.13 (van Kampen squares, adhesive categories). A pushout square (A, B, C, D) is a van Kampen square if for any commutative cube Definition 4.13 A pushout square if for any commutative cube A category has pushouts along monomorphisms if all sources (A, f, g) have pushouts whenever f or g is a monomorphism. A category has pushouts along monomorphisms if all sources (A, f, g) have pushouts whenever f or g is a monomorphism. A category is adhesive if it has pullbacks, pushouts along monomorphisms and all such pushouts are van Kampen squares. A category is adhesive if it has pullbacks, pushouts along monomorphisms and all such pushouts are van Kampen squares. As in the proof that Graphs is adhesive, we will use the fact that the category Sets is adhesive. Graphs Sets Lemma 4.14. E reflects isomorphisms. Lemma 4.14. reflects isomorphisms. A side consequence is that Monogr is balanced, i.e., if f is both a monomorphism and an epimorphism, then by Corollaries 4.3 and 4.7 f is bijective, hence is an isomorphism. More important is that we can use [7, Theorem 24.7], i.e., that a faithful and isomorphism reflecting functor from a category that has some limits or colimits and preserves them, also reflects them. Monogr Lemma 4.15. E preserves and reflects finite colimits. Lemma 4.15. preserves and reflects finite colimits. Proof. It is easy to see from the proofs of Lemmas 4.1 and 4.2 that E preserves both coproducts and coequalizers, so that E preserves all finite co-limits and hence also reflects them. Proof This is particularly true for pushouts. The situation for pullbacks is more complicated since E does not preserve products. Lemma 4.16. E preserves and reflects pullbacks. preserves and reflects pullbacks. Theorem 4.17. The categories of Definition 3.5 are adhesive. Theorem 4.17. The categories of Definition 3.5 are adhesive. Proof. The existence of pullbacks and pushouts is already established. In any of these categories a commutative cube built on a pushout along a monomorphism as bottom face and with pullbacks as back faces, has an underlying cube in Sets that has the same properties by Corollary 4.7, Lemmas 4.15 and 4.16. Since Sets is an adhesive category (see [8]) the underlying bottom face is a van Kampen square, hence such is the bottom face of the initial cube by Lemmas 4.15 and 4.16. Proof Sets Sets This paper is available on arxiv under CC BY 4.0 DEED license. This paper is available on arxiv under CC BY 4.0 DEED license. available on arxiv

Part of HackerNoon's growing list of open-source research papers, promoting free access to academic material.

Abstract

Every

Lemma

Theorem

A Guide to Naming and Mapping Monographs

How Monographs Unify Graph Structures

Read My Stories

Too Long; Didn't Read

Boost your HackerNoon story @ $159.99! 🚀

A Structural Analysis of Limits and Colimits in Monographs

About Author

Comments

TOPICS

THIS ARTICLE WAS FEATURED IN

Related Stories

Untitled Story

A Guide to Naming and Mapping Monographs

The Algebra of Everything

The Building Blocks of Graph Structures

How Monographs Unify Graph Structures

A Guide to Naming and Mapping Monographs

A Guide to Naming and Mapping Monographs

The Algebra of Everything

The Building Blocks of Graph Structures

How Monographs Unify Graph Structures

A Guide to Naming and Mapping Monographs

Light-Mode

Classic

Newspaper

Dark-Mode

Neon Noir

Minty

HN StartUps