In category theory, a branch of mathematics, duality is a correspondence between properties of a category C and so-called dual properties of the opposite categoryCop. Given a statement regarding the category C, by interchanging the source and target of each morphism as well as interchanging the order of composing two morphisms, a corresponding dual statement is obtained regarding the opposite category Cop. Duality, as such, is the assertion that truth is invariant under this operation on statements. In other words, if a statement is true about C, then its dual statement is true about Cop. Also, if a statement is false about C, then its dual has to be false about Cop.
Given a concrete categoryC, it is often the case that the opposite category Cop per se is abstract. Cop need not be a category that arises from mathematical practice. In this case, another category D is also termed to be in duality with C if D and Cop are equivalent as categories.
In the case when C and its opposite Cop are equivalent, such a category is self-dual.
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is…duality in categories? Or: Rigid and pivotal categories.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Rigid and pivotal categories.
https://en.wikipedia.org/wiki/Rigid_category
https://ncatlab.org/nlab/show/rigid+monoidal+cat...
published: 08 Mar 2022
Category Theory For Beginners: Duality And Functors
In this video we introduce the idea of duality, and the notion of the opposite category. We define the initial object of a category, and show that it can be viewed as the empty set, within the category of sets. We also introduce the idea of the coproduct and show that it corresponds to the discriminated union, within the category of sets. We also show how the Cartesian product can be viewed as a functor in the category of sets. More generally, we show that the categorical product can be viewed as a functor, when the categorical product of each pair of objects is defined. This also gives us a notion of the categorical product of a pair of arrows.
published: 03 Jun 2019
Takt Category Theory Session 13: Duality and Coproducts
We go over the first two sections of chapter 3 in Awodey's "Category Theory".
published: 02 Feb 2017
A Sensible Introduction to Category Theory
Remember when I used a video with a coconut in the thumbnail to drive a stake through the heart of mathematical structure? Today, in this introduction to the basics of category theory, I attempt to remove it.
27 Unhelpful Facts About Category Theory: https://www.youtube.com/watch?v=H0Ek86IH-3Y
MetaMaths on category theory: https://www.youtube.com/watch?v=ZG6t0-JMrw0
My dissertation on the equivalence between the category of monoidal categories and the category of representable multicategories: https://drive.google.com/file/d/1hAkV1qSnUutzQMMQi48yo_fXsgb1YnbL/view?usp=sharing
FURTHER READING
Basic Category Theory (Tom Leinster): https://arxiv.org/pdf/1612.09375.pdf
Categories for the Working Mathematician (Saunders Mac Lane): http://www.mtm.ufsc.br/~ebatista/2016-2/maclanecat.pdf
Catego...
Limits and Adjoints in Category theory ; Stone duality in propositional logic
Limits and Adjoints in Category theory by Dipankar Maity and Animesh Renanse; Stone duality in propositional logic by Prof. Mohua Banerjee
published: 18 May 2022
What is...the duality principle?
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is...the duality principle? Or: Flipping arrows.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Nonsense.
On the “Transposing matrices” slide: Transposing matrices does not change entries from 3→2. No idea how that typo happened...
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.htm...
published: 23 Nov 2021
Category Theory Part 1 of 3: Categories
An introduction to categories, functors, universal properties, natural transformations, and monads with applications to the lambda calculus and functional programming.
This video is part 1 of a series:
https://youtube.com/playlist?list=PL6kPvEdcJ4jTXsLMBy-1E8CIalh5DCc6B
Read more here: https://github.com/blargoner/math-categories/blob/main/categories.pdf
published: 25 May 2020
Categories 1 Introduction
This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The lectures were originally part of a graduate algebra course, and give a quick overview of the basic category theory that is useful in algebra.
Recommended textbook: "Categories for the working mathematician", by S. Mac Lane.
For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj51F9XZ_Ka4bLnQoxTdMx0AL
published: 20 Sep 2021
What does categorical dual mean?
What does categorical dual mean?
A spoken definition of categorical dual.
Intro Sound:
Typewriter - Tamskp
Licensed under CC:BA 3.0
Outro Music:
Groove Groove - Kevin MacLeod (incompetech.com)
Licensed under CC:BA 3.0
Intro/Outro Photo:
The best days are not planned - Marcus Hansson
Licensed under CC-BY-2.0
Book Image:
Open Book template PSD - DougitDesign
Licensed under CC:BA 3.0
Text derived from:
http://en.wiktionary.org/wiki/categorical_dual
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is…duality in categories? Or: Rigid and pivotal categories.
Disclaim...
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is…duality in categories? Or: Rigid and pivotal categories.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Rigid and pivotal categories.
https://en.wikipedia.org/wiki/Rigid_category
https://ncatlab.org/nlab/show/rigid+monoidal+category
https://ncatlab.org/nlab/show/pivotal+category
https://math.stackexchange.com/questions/4010759/pivotal-category-why-that-name
Monoidal categories.
https://en.wikipedia.org/wiki/Monoidal_category
https://nlab-pages.s3.us-east-2.amazonaws.com/nlab/show/monoidal+category
https://ocw.mit.edu/courses/mathematics/18-769-topics-in-lie-theory-tensor-categories-spring-2009/lecture-notes/MIT18_769S09_lec01.pdf
https://www.dtubbenhauer.com/qinvariants.pdf
String diagrams.
https://en.wikipedia.org/wiki/String_diagram
https://ncatlab.org/nlab/show/string+diagram
https://core.ac.uk/download/pdf/21747055.pdf
Pictures used.
Pictures from From http://www.dtubbenhauer.com/qinvariants.pdf
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is…duality in categories? Or: Rigid and pivotal categories.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Rigid and pivotal categories.
https://en.wikipedia.org/wiki/Rigid_category
https://ncatlab.org/nlab/show/rigid+monoidal+category
https://ncatlab.org/nlab/show/pivotal+category
https://math.stackexchange.com/questions/4010759/pivotal-category-why-that-name
Monoidal categories.
https://en.wikipedia.org/wiki/Monoidal_category
https://nlab-pages.s3.us-east-2.amazonaws.com/nlab/show/monoidal+category
https://ocw.mit.edu/courses/mathematics/18-769-topics-in-lie-theory-tensor-categories-spring-2009/lecture-notes/MIT18_769S09_lec01.pdf
https://www.dtubbenhauer.com/qinvariants.pdf
String diagrams.
https://en.wikipedia.org/wiki/String_diagram
https://ncatlab.org/nlab/show/string+diagram
https://core.ac.uk/download/pdf/21747055.pdf
Pictures used.
Pictures from From http://www.dtubbenhauer.com/qinvariants.pdf
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
In this video we introduce the idea of duality, and the notion of the opposite category. We define the initial object of a category, and show that it can be vie...
In this video we introduce the idea of duality, and the notion of the opposite category. We define the initial object of a category, and show that it can be viewed as the empty set, within the category of sets. We also introduce the idea of the coproduct and show that it corresponds to the discriminated union, within the category of sets. We also show how the Cartesian product can be viewed as a functor in the category of sets. More generally, we show that the categorical product can be viewed as a functor, when the categorical product of each pair of objects is defined. This also gives us a notion of the categorical product of a pair of arrows.
In this video we introduce the idea of duality, and the notion of the opposite category. We define the initial object of a category, and show that it can be viewed as the empty set, within the category of sets. We also introduce the idea of the coproduct and show that it corresponds to the discriminated union, within the category of sets. We also show how the Cartesian product can be viewed as a functor in the category of sets. More generally, we show that the categorical product can be viewed as a functor, when the categorical product of each pair of objects is defined. This also gives us a notion of the categorical product of a pair of arrows.
Remember when I used a video with a coconut in the thumbnail to drive a stake through the heart of mathematical structure? Today, in this introduction to the ba...
Remember when I used a video with a coconut in the thumbnail to drive a stake through the heart of mathematical structure? Today, in this introduction to the basics of category theory, I attempt to remove it.
27 Unhelpful Facts About Category Theory: https://www.youtube.com/watch?v=H0Ek86IH-3Y
MetaMaths on category theory: https://www.youtube.com/watch?v=ZG6t0-JMrw0
My dissertation on the equivalence between the category of monoidal categories and the category of representable multicategories: https://drive.google.com/file/d/1hAkV1qSnUutzQMMQi48yo_fXsgb1YnbL/view?usp=sharing
FURTHER READING
Basic Category Theory (Tom Leinster): https://arxiv.org/pdf/1612.09375.pdf
Categories for the Working Mathematician (Saunders Mac Lane): http://www.mtm.ufsc.br/~ebatista/2016-2/maclanecat.pdf
Category Theory for Computing Science (Michael Barr and Charles Wells): https://www.math.mcgill.ca/triples/Barr-Wells-ctcs.pdf
Category Theory for the Sciences (David Spivak): https://math.mit.edu/~dspivak/CT4S.pdf
Bartosz Milewski on category theory: https://www.youtube.com/watch?v=I8LbkfSSR58&list=PLbgaMIhjbmEnaH_LTkxLI7FMa2HsnawM_
Emily Riehl on category theory: https://www.youtube.com/watch?v=WLkMBMUk48E
MUSIC
Meditation Aquatic
369 (Epidemic Sound)
Nights Full of Overthinking
Lionel Quick (Epidemic Sound)
Oregano
Vendla (Epidemic Sound)
Wash
Timothy Infinite (Epidemic Sound)
Wind
Osoku (Epidemic Sound)
Remember when I used a video with a coconut in the thumbnail to drive a stake through the heart of mathematical structure? Today, in this introduction to the basics of category theory, I attempt to remove it.
27 Unhelpful Facts About Category Theory: https://www.youtube.com/watch?v=H0Ek86IH-3Y
MetaMaths on category theory: https://www.youtube.com/watch?v=ZG6t0-JMrw0
My dissertation on the equivalence between the category of monoidal categories and the category of representable multicategories: https://drive.google.com/file/d/1hAkV1qSnUutzQMMQi48yo_fXsgb1YnbL/view?usp=sharing
FURTHER READING
Basic Category Theory (Tom Leinster): https://arxiv.org/pdf/1612.09375.pdf
Categories for the Working Mathematician (Saunders Mac Lane): http://www.mtm.ufsc.br/~ebatista/2016-2/maclanecat.pdf
Category Theory for Computing Science (Michael Barr and Charles Wells): https://www.math.mcgill.ca/triples/Barr-Wells-ctcs.pdf
Category Theory for the Sciences (David Spivak): https://math.mit.edu/~dspivak/CT4S.pdf
Bartosz Milewski on category theory: https://www.youtube.com/watch?v=I8LbkfSSR58&list=PLbgaMIhjbmEnaH_LTkxLI7FMa2HsnawM_
Emily Riehl on category theory: https://www.youtube.com/watch?v=WLkMBMUk48E
MUSIC
Meditation Aquatic
369 (Epidemic Sound)
Nights Full of Overthinking
Lionel Quick (Epidemic Sound)
Oregano
Vendla (Epidemic Sound)
Wash
Timothy Infinite (Epidemic Sound)
Wind
Osoku (Epidemic Sound)
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is...the duality principle? Or: Flipping arrows.
Disclaimer.
Nobody...
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is...the duality principle? Or: Flipping arrows.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Nonsense.
On the “Transposing matrices” slide: Transposing matrices does not change entries from 3→2. No idea how that typo happened...
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Dual and opposite.
https://en.wikipedia.org/wiki/Dual_(category_theory)
https://ncatlab.org/nlab/show/duality
https://en.wikipedia.org/wiki/Opposite_category
https://ncatlab.org/nlab/show/opposite+category
Duality.
https://en.wikipedia.org/wiki/Duality_(mathematics)
Pictures used.
http://www.euclideanspace.com/maths/topology/algtop/cohomology/innerProduct.png
Picture from Chapter 1 of http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://en.wikipedia.org/wiki/Injective_function#/media/File:Injection.svg
https://en.wikipedia.org/wiki/Injective_function#/media/File:Surjection.svg
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is...the duality principle? Or: Flipping arrows.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Nonsense.
On the “Transposing matrices” slide: Transposing matrices does not change entries from 3→2. No idea how that typo happened...
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Dual and opposite.
https://en.wikipedia.org/wiki/Dual_(category_theory)
https://ncatlab.org/nlab/show/duality
https://en.wikipedia.org/wiki/Opposite_category
https://ncatlab.org/nlab/show/opposite+category
Duality.
https://en.wikipedia.org/wiki/Duality_(mathematics)
Pictures used.
http://www.euclideanspace.com/maths/topology/algtop/cohomology/innerProduct.png
Picture from Chapter 1 of http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://en.wikipedia.org/wiki/Injective_function#/media/File:Injection.svg
https://en.wikipedia.org/wiki/Injective_function#/media/File:Surjection.svg
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
An introduction to categories, functors, universal properties, natural transformations, and monads with applications to the lambda calculus and functional progr...
An introduction to categories, functors, universal properties, natural transformations, and monads with applications to the lambda calculus and functional programming.
This video is part 1 of a series:
https://youtube.com/playlist?list=PL6kPvEdcJ4jTXsLMBy-1E8CIalh5DCc6B
Read more here: https://github.com/blargoner/math-categories/blob/main/categories.pdf
An introduction to categories, functors, universal properties, natural transformations, and monads with applications to the lambda calculus and functional programming.
This video is part 1 of a series:
https://youtube.com/playlist?list=PL6kPvEdcJ4jTXsLMBy-1E8CIalh5DCc6B
Read more here: https://github.com/blargoner/math-categories/blob/main/categories.pdf
This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The ...
This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The lectures were originally part of a graduate algebra course, and give a quick overview of the basic category theory that is useful in algebra.
Recommended textbook: "Categories for the working mathematician", by S. Mac Lane.
For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj51F9XZ_Ka4bLnQoxTdMx0AL
This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The lectures were originally part of a graduate algebra course, and give a quick overview of the basic category theory that is useful in algebra.
Recommended textbook: "Categories for the working mathematician", by S. Mac Lane.
For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj51F9XZ_Ka4bLnQoxTdMx0AL
What does categorical dual mean?
A spoken definition of categorical dual.
Intro Sound:
Typewriter - Tamskp
Licensed under CC:BA 3.0
Outro Music:
Groov...
What does categorical dual mean?
A spoken definition of categorical dual.
Intro Sound:
Typewriter - Tamskp
Licensed under CC:BA 3.0
Outro Music:
Groove Groove - Kevin MacLeod (incompetech.com)
Licensed under CC:BA 3.0
Intro/Outro Photo:
The best days are not planned - Marcus Hansson
Licensed under CC-BY-2.0
Book Image:
Open Book template PSD - DougitDesign
Licensed under CC:BA 3.0
Text derived from:
http://en.wiktionary.org/wiki/categorical_dual
What does categorical dual mean?
A spoken definition of categorical dual.
Intro Sound:
Typewriter - Tamskp
Licensed under CC:BA 3.0
Outro Music:
Groove Groove - Kevin MacLeod (incompetech.com)
Licensed under CC:BA 3.0
Intro/Outro Photo:
The best days are not planned - Marcus Hansson
Licensed under CC-BY-2.0
Book Image:
Open Book template PSD - DougitDesign
Licensed under CC:BA 3.0
Text derived from:
http://en.wiktionary.org/wiki/categorical_dual
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is…duality in categories? Or: Rigid and pivotal categories.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Rigid and pivotal categories.
https://en.wikipedia.org/wiki/Rigid_category
https://ncatlab.org/nlab/show/rigid+monoidal+category
https://ncatlab.org/nlab/show/pivotal+category
https://math.stackexchange.com/questions/4010759/pivotal-category-why-that-name
Monoidal categories.
https://en.wikipedia.org/wiki/Monoidal_category
https://nlab-pages.s3.us-east-2.amazonaws.com/nlab/show/monoidal+category
https://ocw.mit.edu/courses/mathematics/18-769-topics-in-lie-theory-tensor-categories-spring-2009/lecture-notes/MIT18_769S09_lec01.pdf
https://www.dtubbenhauer.com/qinvariants.pdf
String diagrams.
https://en.wikipedia.org/wiki/String_diagram
https://ncatlab.org/nlab/show/string+diagram
https://core.ac.uk/download/pdf/21747055.pdf
Pictures used.
Pictures from From http://www.dtubbenhauer.com/qinvariants.pdf
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
In this video we introduce the idea of duality, and the notion of the opposite category. We define the initial object of a category, and show that it can be viewed as the empty set, within the category of sets. We also introduce the idea of the coproduct and show that it corresponds to the discriminated union, within the category of sets. We also show how the Cartesian product can be viewed as a functor in the category of sets. More generally, we show that the categorical product can be viewed as a functor, when the categorical product of each pair of objects is defined. This also gives us a notion of the categorical product of a pair of arrows.
Remember when I used a video with a coconut in the thumbnail to drive a stake through the heart of mathematical structure? Today, in this introduction to the basics of category theory, I attempt to remove it.
27 Unhelpful Facts About Category Theory: https://www.youtube.com/watch?v=H0Ek86IH-3Y
MetaMaths on category theory: https://www.youtube.com/watch?v=ZG6t0-JMrw0
My dissertation on the equivalence between the category of monoidal categories and the category of representable multicategories: https://drive.google.com/file/d/1hAkV1qSnUutzQMMQi48yo_fXsgb1YnbL/view?usp=sharing
FURTHER READING
Basic Category Theory (Tom Leinster): https://arxiv.org/pdf/1612.09375.pdf
Categories for the Working Mathematician (Saunders Mac Lane): http://www.mtm.ufsc.br/~ebatista/2016-2/maclanecat.pdf
Category Theory for Computing Science (Michael Barr and Charles Wells): https://www.math.mcgill.ca/triples/Barr-Wells-ctcs.pdf
Category Theory for the Sciences (David Spivak): https://math.mit.edu/~dspivak/CT4S.pdf
Bartosz Milewski on category theory: https://www.youtube.com/watch?v=I8LbkfSSR58&list=PLbgaMIhjbmEnaH_LTkxLI7FMa2HsnawM_
Emily Riehl on category theory: https://www.youtube.com/watch?v=WLkMBMUk48E
MUSIC
Meditation Aquatic
369 (Epidemic Sound)
Nights Full of Overthinking
Lionel Quick (Epidemic Sound)
Oregano
Vendla (Epidemic Sound)
Wash
Timothy Infinite (Epidemic Sound)
Wind
Osoku (Epidemic Sound)
Goal.
Explaining basic concepts of category theory in an intuitive way.
This time.
What is...the duality principle? Or: Flipping arrows.
Disclaimer.
Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references.
Disclaimer.
The distinction between “large classes” and “small classes (sets)” turns out is crucial for many categorical considerations, but somehow makes the language more cumbersome without too much gain imho. So I will strategically ignore all set-theoretical issues.
Nonsense.
On the “Transposing matrices” slide: Transposing matrices does not change entries from 3→2. No idea how that typo happened...
Slides.
http://www.dtubbenhauer.com/youtube.html
Website with exercises.
http://www.dtubbenhauer.com/lecture-ct-2022.html
Dual and opposite.
https://en.wikipedia.org/wiki/Dual_(category_theory)
https://ncatlab.org/nlab/show/duality
https://en.wikipedia.org/wiki/Opposite_category
https://ncatlab.org/nlab/show/opposite+category
Duality.
https://en.wikipedia.org/wiki/Duality_(mathematics)
Pictures used.
http://www.euclideanspace.com/maths/topology/algtop/cohomology/innerProduct.png
Picture from Chapter 1 of http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://en.wikipedia.org/wiki/Injective_function#/media/File:Injection.svg
https://en.wikipedia.org/wiki/Injective_function#/media/File:Surjection.svg
Some books I am using (I sometimes steal some pictures from there).
https://en.wikipedia.org/wiki/Categories_for_the_Working_Mathematician
https://www.cambridge.org/core/books/an-introduction-to-category-theory/38C6B02892C2FE7408F52975756AC88D
http://www.tac.mta.ca/tac/reprints/articles/17/tr17.pdf
https://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf
https://math.jhu.edu/~eriehl/context.pdf
https://github.com/hmemcpy/milewski-ctfp-pdf
Nlab.
https://ncatlab.org/nlab/show/HomePage
TheCatsters.
https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA
Mathematica.
https://wildcatsformma.wordpress.com/
#categorytheory
#categoricalalgebra
#mathematics
An introduction to categories, functors, universal properties, natural transformations, and monads with applications to the lambda calculus and functional programming.
This video is part 1 of a series:
https://youtube.com/playlist?list=PL6kPvEdcJ4jTXsLMBy-1E8CIalh5DCc6B
Read more here: https://github.com/blargoner/math-categories/blob/main/categories.pdf
This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The lectures were originally part of a graduate algebra course, and give a quick overview of the basic category theory that is useful in algebra.
Recommended textbook: "Categories for the working mathematician", by S. Mac Lane.
For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj51F9XZ_Ka4bLnQoxTdMx0AL
What does categorical dual mean?
A spoken definition of categorical dual.
Intro Sound:
Typewriter - Tamskp
Licensed under CC:BA 3.0
Outro Music:
Groove Groove - Kevin MacLeod (incompetech.com)
Licensed under CC:BA 3.0
Intro/Outro Photo:
The best days are not planned - Marcus Hansson
Licensed under CC-BY-2.0
Book Image:
Open Book template PSD - DougitDesign
Licensed under CC:BA 3.0
Text derived from:
http://en.wiktionary.org/wiki/categorical_dual
In category theory, a branch of mathematics, duality is a correspondence between properties of a category C and so-called dual properties of the opposite categoryCop. Given a statement regarding the category C, by interchanging the source and target of each morphism as well as interchanging the order of composing two morphisms, a corresponding dual statement is obtained regarding the opposite category Cop. Duality, as such, is the assertion that truth is invariant under this operation on statements. In other words, if a statement is true about C, then its dual statement is true about Cop. Also, if a statement is false about C, then its dual has to be false about Cop.
Given a concrete categoryC, it is often the case that the opposite category Cop per se is abstract. Cop need not be a category that arises from mathematical practice. In this case, another category D is also termed to be in duality with C if D and Cop are equivalent as categories.
In the case when C and its opposite Cop are equivalent, such a category is self-dual.