比利时vs摩洛哥足彩
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university of california san diego
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algebraic geometry seminar
anton geraschenko
when is a variety a quotient of a smooth variety by a finite group?
abstract:
\indent if a variety $x$ is a quotient of a smooth variety by a finite group, it has quotient singularities---that is, it is \emph{locally} a quotient by a finite group. in this talk, we will see that the converse is true if $x$ is quasi-projective and is known to be a quotient by a torus. in particular, all quasi-projective simplicial toric varieties are global quotients by finite groups! though the proof is stack-theoretic, the construction of a smooth variety $u$ and finite group $g$ so that $x=u/g$ can usually be made explicit purely scheme-theoretically. \indent to illustrate the construction, i'll produce a smooth variety $u$ with an action of $g=\mathbb{z}/2$ so that $u/g$ is the blow-up of $\mathbb{p}(1,1,2)$ at a smooth point. this example is interesting because even though $u/g$ is toric, $u$ cannot be taken to be toric. this is joint work with matthew satriano.
october 26, 2011
4:00 pm
ap&m 7218
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