Quadric bundles and their moduli spaces
  Quadric bundles on a compact Riemann surface X generalise orthogonal bundles and arise naturally in the study of the moduli space of representations of $\pi_1(X)$ in Sp(2n,R). We prove some basic results on the moduli spaces of quadric bundles over X of arbitrary rank and then survey deeper results in the rank 2 case. 
Andr\'e Oliveira
math.AG