Published online by Cambridge University Press: 20 November 2018
Let $E$ be a stable rank 2 vector bundle on a smooth projective curve $X$ and $V\,\left( E \right)$ be the set of all rank 1 subbundles of $E$ with maximal degree. Here we study the varieties (non-emptyness, irreducibility and dimension) of all rank 2 stable vector bundles, $E$, on $X$ with fixed $\deg \left( E \right)$ and $\deg \left( L \right),\,L\,\in \,V\left( E \right)$ and such that $\text{card}\,\left( V(E) \right)\,\ge \,2\,(\text{resp}\text{. card}\left( V(E) \right)\,=\,2)$.