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Jan
8
revised Betti number and the homology class - what determines the coefficient $Q$?
edited tags
Jan
8
comment Confused over k-chains and their boundaries.
That is not the correct definition of $\partial C$ in this situation. See the definition of e.g. singular homology.
Jan
7
awarded  Investor
Jan
7
revised Module of differentials in the functorial approach to schemes and quasi-coherent modules
deleted 8 characters in body
Jan
7
comment Construction of Yoneda extension
It's a bit difficult to define directly, but it can be done if you really want to. It's easier to describe the right adjoint and describe the left adjoint in terms of that.
Jan
6
comment Why does the fixed point theorem hold for every lambda term?
Very simply: $\lambda$-terms are not the same as numerical functions.
Jan
6
comment Path structure of an odd-looking higher inductive type.
Ah, good point. I was just thinking of iterates of nest. So perhaps it should be the free "group with an endomap" on one element?
Jan
6
comment Path structure of an odd-looking higher inductive type.
I suspect this defines a rose of infinitely many circles.
Jan
5
comment Rel is a concrete category over Sets, but how to concretize that?
This is an explicit description.
Jan
5
answered Rel is a concrete category over Sets, but how to concretize that?
Jan
5
revised mapping cone and cylinder
edited tags
Jan
5
revised Precomposing a rational function $f$ with a birational isomorphism $g$ to make $f\circ g$ regular?
added 33 characters in body
Jan
5
answered Precomposing a rational function $f$ with a birational isomorphism $g$ to make $f\circ g$ regular?
Jan
5
comment Hom$_{Set}(G \times H,R) \cong $Hom$_{Set}(G,R)\otimes $ Hom$_{Set}(H,R)$?
OK, but now where are you using the fact that you have groups?
Jan
5
revised What is the algebraic tangent cone really?
added 12 characters in body
Jan
4
asked What is the algebraic tangent cone really?
Jan
3
answered A question on Mumford's drawing of $\text{Spec}\,\mathbb{Z}[x]$
Jan
3
comment Is there a system of mathematics where everything is a function?
That's just syntax. Variables are not "real" entities.
Jan
2
answered Sheafication of a presheaf
Jan
2
comment Is there a system of mathematics where everything is a function?
In untyped lambda calculus, everything is a function. (There are no sets!)