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Apr
19
comment A Hartogs-type criterion for flatness
Quotients by finite group actions give counter examples in the general case, e.g. see the answer to this question: mathoverflow.net/questions/169052/… Take $U = k^2$, $V = U\setminus$origin, $Y = $ image of $V$ by the quotient map.
Apr
13
comment Is this method of finding a “dual curve” correct?
Well, $(\Gamma^*)^* = \Gamma$, and $[a(t) : b(t):1]$ are points on $\Gamma$, so unless I am missing something, by definition of duality, the tangents to $\Gamma^*$ are precisely (modulo taking the closure) the lines $\{[x:y:1]: a(t)x + b(t)y + 1 = 0\}$.
Mar
22
comment A question about homogenous polynomials of degree $\frac{n(n-1)}{2}$
Can you elaborate on what can be expected to be known about $f$? E.g: do you know a factorization, and expansions of the factors (as in your example)? Can you evaluate $f$ at (finite) sets of points?
Mar
10
revised Resolution of the $E_8$ singularity with a weighted blowup
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Mar
8
answered Resolution of the $E_8$ singularity with a weighted blowup
Feb
25
awarded  Nice Question
Feb
3
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Nov
23
awarded  Nice Question
Nov
19
comment Standard polynomials applied to matrices (bis)
How do you get a map from $M_2(\mathbb{R})$ to itself via $S_2$? Do you fix one of the factors?
Nov
17
awarded  Popular Question
Nov
5
awarded  Yearling
Oct
22
awarded  Popular Question
Oct
22
answered Can a curve intersect a given curve only at given points?
Oct
21
awarded  Enlightened
Oct
21
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Jun
5
revised When is $f(x^d)$ irreducible?
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Jun
5
revised When is $f(x^d)$ irreducible?
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Jun
5
answered When is $f(x^d)$ irreducible?
Jun
5
accepted The space of polynomials with all real roots
Jun
5
revised The space of polynomials with all real roots
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