Tautological algebra of the moduli stack of semi stable bundles of rank two on a general curve

Abstract: Our aim in this paper is to determine the tautological algebra generated by the cohomology classes of the Brill Noether loci in the rational cohomology of the moduli stack $\mathcal{U}_C(n,d)$ of semistable bundles of rank $n$ and degree $d$. When $C$ is a general smooth projective curve of genus $g\geq 2$, $n=2$, $d=2g-2$, the tautological algebra of $ \mathcal{U}_C(2,2g-2)$ (resp. $\mathcal{SU}_C(2,L)$, $deg(L)=2g-2)$) is generated by the divisor classes (resp. the Theta divisor $\Theta$).