2,440 reputation
1721
bio website wildcatsformma.wordpress.com
location Somewhere over the rainbow
age
visits member for 3 years, 2 months
seen 8 hours ago

My scientific interests:

  • Mathematics: Category Theory, Algebra, Logic (Model-Theory, ATP), Control Systems
  • Physics: General Relativity, QFT
  • Amateur Astronomer and Astrophotographer
  • Mathematica programming

My Website:WildCats
Premiere Mathematica package for category theory

Visit the newly launched Mathematica.SE!

My non-scientific interests:

  • Skiing, Sailing, Windsurfing
  • Argentine Tango dancer

More or less fluent in (random order):

Italian, English, German, French, Spanish, Dutch and struggling with Russian


Oct
6
comment Completing a Partially Defined Associative Binary Operation
Any chance of finding them online? Maybe in the original Russian version?
Oct
6
suggested rejected edit on Catagorical Definition of Coproduct and Abelian Groups
Oct
6
answered Which books to study category theory?
Sep
29
comment Question on category theory
....So you cannot have a giant category that contains itself (since it contains all categories). The way out is to have hierarchies of collections: sets, classes, conglomerates. You can have the class of all sets and the conglomerate of all classes, but not the set of all sets or the class of all classes. See The Joy of Cats katmat.math.uni-bremen.de/acc/acc.pdf for an eye-opening view on the quasicategory of all categories.
Sep
29
comment Question on category theory
Daniel Rust' answer is clear and simple and adequately answers your question. I just would like to add that the definition you have been given is not the most general one. What you are working with are generally called locally small categories. In any case, it is pretty obvious that you cannot make the category of all categories, for exactly the same reason that you cannot have the set of all sets or the mother of all mothers for that matter. The reason is simply that such things would have to contain themselves and this is a little awkward, and is considered unacceptable. ....
Sep
27
comment Hatcher chapter 0 exercise.
You are welcome. I have't received your email yet :-)
Sep
27
revised Hatcher chapter 0 exercise.
edited small typo
Sep
27
suggested approved edit on Hatcher chapter 0 exercise.
Sep
27
comment Hatcher chapter 0 exercise.
+1 I like your categorical point of view
Sep
26
comment $A$ retract of $X$ and $X$ contractible implies $A$ contractible.
you may contact me per email if you would like to discuss this further
Sep
26
comment $A$ retract of $X$ and $X$ contractible implies $A$ contractible.
Jammer! (what a pity!) Check my profile if you like to en-joy the cats with a Computer Algebra System (Mathematica).
Sep
26
comment $A$ retract of $X$ and $X$ contractible implies $A$ contractible.
Leuk! (=nice in Dutch). Can you suggest some source where homotopy theory or $hTop$ or algebraic topology are developed using the language of categories?
Sep
26
revised $A$ retract of $X$ and $X$ contractible implies $A$ contractible.
edited first par. in second part to keep it in line with the rest of the answer. Slightly edited 2nd par. in first part for clarity.
Sep
26
suggested approved edit on $A$ retract of $X$ and $X$ contractible implies $A$ contractible.
Sep
20
comment Why is every category not isomorphic to its opposite?
Right, needless to say that the only morphism going into the empty set is its own identity, which is indeed an iso.
Sep
18
comment Does the comma category functor have an adjoint?
Sorry but your proof does not hold. You make 2 mistakes: 1) $[A, C] = [B, C]= C^1$ is not $\mathrm{Set}(\mathrm{ob} \ C)$ , it is exactly the category $C$ itself. 2) $s\downarrow t= Hom(s, t)$ is the discrete category whose objects are the morphisms from s to t and only has the identity morphisms. When you then rewrite the adjoint iso, you see that it actually holds if we set $F(X) = s$. The category $\mathrm{Arr}(s, t))$ that you mention is actually $C\downarrow C$ also known as $C^2$.
Sep
15
comment Equalizers and Basic limit theorem in Category theory
@Did I know, and I did it! But as I said it was rejected. I am glad it is fixed now.
Sep
14
awarded  Citizen Patrol
Sep
14
comment Equalizers and Basic limit theorem in Category theory
....@Did and has nothing to do with category theory. So the current title is misleading. I tried to edit it yesterday, but apparently some (half asleep?) moderator did not accept it. Besides, as you point out, the OP himself calls it BASIC limit theorem in the body. So please some other moderator should consider reaccepting my edit or at least fix the title appropriately.
Sep
14
comment Equalizers and Basic limit theorem in Category theory
@Did Exactly!!! The central limit theorem is a fundamental result in statistics en.wikipedia.org/wiki/Central_limit_theorem