Higher secant varieties of $\mathbb P^n \times\mathbb P^ 1$ embedded in   bi-degree $(a,b)$
  In this paper we compute the dimension of all the higher secant varieties to the Segre-Veronese embedding of $\mathbb{P}^n\times \mathbb{P}^1$ via the section of the sheaf $\mathcal{O}(a,b)$ for any $n,a,b\in \mathbb{Z}^+$. We relate this result to the Grassmann Defectivity of Veronese varieties and we classify all the Grassmann $(1,s-1)$-defective Veronese varieties. 
Edoardo Ballico, Alessandra Bernardi, Maria Virginia Catalisano
math.AG math.AC