Moduli of Twisted Orbifold Sheaves and the Period-index Problem
نویسندگان
چکیده
We prove that certain stacks of slope-semistable twisted sheaves on orbisurfaces are non-empty and geometrically irreducible. Using these results, we prove the standard period-index conjecture for Brauer classes over function fields of surfaces over finite fields.
منابع مشابه
Moduli of Twisted Orbifold Sheaves
We study stacks of slope-semistable twisted sheaves on orbisurfaces with projective coarse spaces and prove that in certain cases they have many of the asymptotic properties enjoyed by the moduli of slope-semistable sheaves on smooth projective surfaces.
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Let X be a smooth projective variety over C. Let α := {αijk ∈ H(Ui ∩ Uj ∩ Uk,O X)} be a 2-cocycle representing a torsion class [α] ∈ H2(X,O X). An α-twisted sheaf E := {(Ei, φij)} is a collection of sheaves Ei on Ui and isomorphisms φij : Ei|Ui∩Uj → Ej|Ui∩Uj such that φii = idEi , φji = φ ij and φki ◦ φjk ◦ φij = αijk idEi . We assume that there is a locally free α-twisted sheaf, that is, α giv...
متن کامل/ 95 09 01 4 v 1 4 S ep 1 99 5 March 1995 QMW - TH - 95 - 29 . SPECIAL GEOMETRY AND TWISTED MODULI IN ORBIFOLD THEORIES WITH CONTINUOUS WILSON LINES
Target space duality symmetries, which acts on Kähler and continuous Wilson line moduli, of a Z N (N = 2) 2-dimensional subspace of the moduli space of orbifold compactification are modified to include twisted moduli. These spaces described by the cosets SU (n,1) SU (n)×U (1) are special Kähler, a fact which is exploited in deriving the extension of tree level duality transformation to include ...
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تاریخ انتشار 2009