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seen Feb 7 '13 at 18:18

Nov
17
revised Why do number rings have no endomorphisms
deleted 393 characters in body
Nov
17
asked Why do number rings have no endomorphisms
Nov
13
revised When does a ring have a flat noetherian extension?
added 15 characters in body
Nov
13
comment When does a ring have a flat noetherian extension?
Actually, let me take that back. That can't be correct. What about taking $B$ to be the localization of $A$ at some minimal prime ideal? In this case $B$ is a local zero-dimensional ring. Aren't these always noetherian?
Nov
13
answered When does a ring have a flat noetherian extension?
Nov
8
comment Do K3-surfaces have Weierstrass equations
I don't understand your comment on "birational equivalence" being the same as "isomorphism". I'm trying to say that we need to restrict to an open, or maybe to an open of some blow-up. Certainly this is necessary if we would want a Weierstrass equation in that form. This is already the case for elliptic curves.
Nov
7
asked Do K3-surfaces have Weierstrass equations
Nov
6
comment Coordinate ring of an affine quasi projective variety
The notation for the zero locus of $f$ in $\mathbf{P}^n$ is $V_+(f)$ or $Z_+(f)$ in general.
Nov
6
comment Coordinate ring of an affine quasi projective variety
An affine variety is quasi-projective. (If $X$ is closed in $\mathbf{A}^n$, then it is a closed of an open of $\mathbf{P}^n$. Thus, it is quasi-projective.)
Nov
5
comment Is $M_g$ NEVER proper? And why does $T_g$ contain products?
Another related reference is Matthieu Romagny's notes on models of curves: perso.univ-rennes1.fr/matthieu.romagny/articles/…
Nov
5
comment Is $M_g$ NEVER proper? And why does $T_g$ contain products?
See page 3 and page 4 in Dan Edidin's amazing notes on the moduli space of curves: math.missouri.edu/~edidin/Papers/mfile.pdf
Nov
5
comment Does an irreducible polynomial in K(t)[x] give an irreducible polynomial in K[t][x]
Ow that looks helpful. I think it implies that if I take $a$ to be the least common multiple of the denominators of the coefficients of f (which lie in $K(t)$) we get that the polynomial $af$ is irreducible. In fact, it is irreducible in $K(t)[x]$ (because we're just multiplying by an element in $K(t)$) and it is primitive in $K[t,x]$.
Nov
5
asked Does an irreducible polynomial in K(t)[x] give an irreducible polynomial in K[t][x]
Oct
31
accepted Factorizing rational functions of curves
Oct
26
accepted Representing a curve as a plane curve in different ways
Oct
26
asked Factorizing rational functions of curves
Oct
23
accepted Does de Franchis' theorem hold over any base field
Oct
22
revised Do Neron models of hyperbolic curves exist
added 148 characters in body
Oct
22
comment Does de Franchis' theorem hold over any base field
I can't remember...I think sometimes people also use it for an integral curve whose normalization is a smooth projective geometrically connected curve of genus $\geq 2$.
Oct
22
comment Does de Franchis' theorem hold over any base field
A smooth projective geometrically connected curve of genus $\geq 2$.