# Brauer group of a moduli space of parabolic vector bundles over a curve

Research paper by **Indranil Biswas, Arijit Dey**

Indexed on: **24 Dec '10**Published on: **24 Dec '10**Published in: **Mathematics - Algebraic Geometry**

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#### Abstract

Let ${\mathcal P}{\mathcal M}^\alpha_s$ be a moduli space of stable parabolic
vector bundles of rank $n \geq 2$ and fixed determinant of degree $d$ over a
compact connected Riemann surface $X$ of genus $g(X) \geq 2$. If $g(X) = 2$,
then we assume that $n > 2$. Let $m$ denote the greatest common divisor of $d$,
$n$ and the dimensions of all the successive quotients of the quasi-parabolic
filtrations. We prove that the cohomological Brauer group ${\rm Br}({\mathcal
P}{\mathcal M}^\alpha_s)$ is isomorphic to the cyclic group ${\mathbb Z}/
m{\mathbb Z}$. We also show that ${\rm Br}({\mathcal P}{\mathcal M}^\alpha_s)$
is generated by the Brauer class of the projective bundle over ${\mathcal
P}{\mathcal M}^\alpha_s$ obtained by restricting the universal projective
bundle over $X\times {\mathcal P}{\mathcal M}^\alpha_s$. We also prove that
there is a universal vector bundle over $X\times {\mathcal P}{\mathcal
M}^\alpha_s$ if and only if $m=1$.