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Jan
14
awarded  Necromancer
Dec
15
answered Cone of an adjunction
Dec
15
comment Cone of an adjunction
It means the mapping cone, in the sense of triangulated categories.
Dec
4
comment When should one learn about $(\infty,1)$-categories?
I like Emily Riehl's notes from the YTM for learning about $(\infty,1)$-categories model independently, @QiaochuYuan.
Dec
1
reviewed Reject How to find mean and covariance for a multivariate Gaussian under a linear transformation W?
Nov
22
comment Can any category be imbedded in a balanced category?
I guess I answered the question in the title but went against the spirit of the body of the post, @Qiaochu.
Nov
22
answered Can any category be imbedded in a balanced category?
Nov
3
comment “Comparing” fixed point Theorems.
The fixed point in Brouwer's theorem need not be unique.
Oct
30
comment coequalizers and cofiber in a quasicategory
This is crazy, @user90219: I had completely forgotten I had already answered this question on MathOverflow two years ago! That time I got confused about how to prove the first left hand square was a pushout and Akhil Matthew gave the argument in a comment. I'm glad to see I learned the proof even if I forgot where I learned it. Also, apparently that time I used the row-vector convention for matrices instead...
Oct
30
comment Why does a group homomorphism preserve more structure than a monoid homomorphism while satisfying fewer equations
All the math is correct in this answer but your claim about history, namely that the most common common way people have presented groups is as having three operations, seems false to me. I remember being taught that a group is a binary operation such that there exists a unit and for each element there exists at least one other element called its inverse, etc. I'm pretty sure that is the most common way to present them, at least in classes and textbooks.
Oct
30
comment Is every equivalence of monoidal categories a monoidal equivalence?
To be more explicit, any example of a bijection between monoids which is not a monoid homomorphism is also and example of an equivalence between discrete monoidal categories which is not monoidal.
Oct
29
answered coequalizers and cofiber in a quasicategory
Oct
22
comment homotopy between constant simplicial sets
You only need the codomain to be discrete for this to be true.
Oct
21
comment Serre quotient category
I couldn't quickly figure it out without using elements either, @3A's. :) That might make a good bonus challenge question.
Oct
21
answered Serre quotient category
Oct
20
comment Natural Isomorphism $(V\otimes W)^*\cong V^*\otimes W^*$
Oh, thanks! I assume that "endlichdimensionale" means finite-dimensional, right? You omitted that part from your question!
Oct
19
comment $\otimes$-Categorical Generalization of Lagrange
My impression is that'll take @MartinBrandenburg himself to answer what he meant by that remark. :)
Oct
19
comment Natural Isomorphism $(V\otimes W)^*\cong V^*\otimes W^*$
I'm curious to see the precise wording on Wikipedia: where did you find that statement?
Oct
17
awarded  Informed
Aug
11
awarded  Yearling