16 mar 2018 -- 14:30
Aula Vitali, Dipartimento di Matematica, Università di Bologna
Binary real forms of degree d admit as typical ranks all the integers between $\lfloor d/2 \rfloor +1 $ and $d$. We investigate the boundary between the open subset of rank $r$ forms and the open subset of rank $r+1$. These boundaries are known only in the extreme cases, by Lee-Sturmfels (between rank $\lfloor d/2 \rfloor +1 $ and $\lfloor d/2 \rfloor +2 $ and Comon-Ottaviani (between rank $ d-1 $ and $ d $). We investigate the intermediate boundaries. In the talk I will present our new results, focusing on the case of degree 7 forms. This is work in progress with G.Stagliano'.