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seen Apr 16 at 11:18

Mar
25
comment Jacobian of an injective mapping
@user126154: you are right. I saw in the question $J_f(a) < 0$, and immediately interpreted $J_f$ as the Jacobian determinant.
Mar
25
comment Jacobian of an injective mapping
@user126154: I meant the function $\phi: \mathbb{R} \to \mathbb{R}$ defined by $\phi(t) := J_f(a + t(b-a))$.
Mar
25
comment Jacobian of an injective mapping
For the 2nd question apply the intermediate value theorem to $J_f$-restricted to the line joining a and b.
Mar
12
accepted Why the name “variety” and the notation “V” for zeroes of polynomials?
Mar
11
awarded  Nice Question
Mar
11
asked Why the name “variety” and the notation “V” for zeroes of polynomials?
Mar
10
comment Normal polytopes - counterexample?
Regarding the 'related question': M = dim(P) -1 suffices (Theorem 2.2.12, Toric Varieties, Cox-Little-Schenck).
Feb
19
comment What are some mathematical sculptures?
@ToddTrimble: Hi Todd, it had a "coppery" look, but not sure if it was mixed with anything else.
Feb
4
accepted How many of the true sentences are provable?
Feb
1
awarded  Enlightened
Feb
1
awarded  Nice Answer
Jan
31
comment Is the induced ring homomorphism surjective for a finite injective morphism between affine varieties?
Just wanted to add that in your first statement above, "affine" is not necessary. Essentially the same argument shows that "a finite bijective morphism f:X→Y between varieties where Y is normal must be an isomorphism."
Jan
31
revised Is the induced ring homomorphism surjective for a finite injective morphism between affine varieties?
added 428 characters in body
Jan
31
answered Is the induced ring homomorphism surjective for a finite injective morphism between affine varieties?
Nov
28
comment Computing fundamental groups of the complement of plane curves
@Jason: I see I was being dense. Thanks again.
Nov
28
revised Computing fundamental groups of the complement of plane curves
added 32 characters in body
Nov
28
comment Computing fundamental groups of the complement of plane curves
@Ian: Thanks - I will take a look.
Nov
28
comment Computing fundamental groups of the complement of plane curves
@Jason: I don't think I have written anything wrong. In any event, I edited the question to make it (hopefully) clearer. Thanks.
Nov
28
revised Computing fundamental groups of the complement of plane curves
added 367 characters in body
Nov
28
comment Computing fundamental groups of the complement of plane curves
@Jack: You are right. But I want to know how, for a fixed (not necessarily nice) $C$, to choose $D$ so that every loop in $\mathbb{P}^2-C$ can be deformed into a loop in $D-C$. Even in this case $D$ can be chosen to be a generic line. But can we take it to be a generic element in any other linear system (not necessarily containing lines)?