# category theory

1. ### A Structure preserved by strong equivalence of metrics?

Let $d_1$ and $d_2$ be two metrics on the same set $X$. We say that $d_1$ and $d_2$ are equivalent if the identity map from $(X,d_1)$ to $(X,d_2)$ and its inverse are continuous. We say that they’re uniformly equivalent if the identity map and its inverse are uniformly...
2. ### A Taxonomy of Theories in Theoretical Physics

It goes without saying that theoretical physics has over the years become overrun with countless distinct - yet sometimes curiously very similar - theories, in some cases even dozens of directly competing theories. Within the foundations things can get far worse once we start to run into...
3. ### I System to represent objects in Mathematics

Hi. Usually, Computer Programmers use Flow Charts, Algorithms, or UML diagrams to build a great software or system. In the same manner, in Mathematics, what do Mathematicians use to build a great system that they want to build. Category Theory is at the highest level of abstraction; then...
4. ### Algebra Categories for the Working Mathematician

Hello. I am about to start learning category theory. I keep hearing mixed opinions on the book Categories for the Working Mathematician, by Sanders MacLane (I am aware he is one of the founders of the theory). Some say it's a "must read", and others have called it "outdated." What would seem...
5. ### Understanding the Coproduct in Grp as a Universal Object

1. Homework Statement Coproducts exist in Grp. This starts on page 71. of his Algebra. 2. Homework Equations Allow me to present the proof in it's entirety, modified only where it's convenient or necessary for TeXing it. I've underlined areas where I have issues and bold bracketed off my...
6. ### $\hom_A(-,N)$Functor Takes Coproducts to Products

A couple of notes first: 1. \hom_{A}(-,N) is the left-exact functor I'm referring to; Lang gives an exercise in the section preceeding to show this. 2. This might be my own idiosyncrasy but I write TFDC to mean 'The following diagram commutes' 3. Titles are short, so I know that the hom-functor...