Zev Rosengarten

collaborators

8 papers

math.AG2026

Extensions Of Unirational Groups

Zev Rosengarten

We undertake a study of extensions of unirational algebraic groups. We prove that extensions of unirational groups are also unirational over fields of degree of imperfection $1$ , b…

math.AG2025

Algebraic Groups with Torsors That Are Versal for All Affine Varieties

Uriya A. First, Mathieu Florence, Zev Rosengarten

Let $k$ be a field and let $G$ be an affine algebraic group over $k$ . Call a $G$ -torsor weakly versal for a class of $k$ -schemes $C$ if it specializes to every $G$ -torsor over…

math.NT2025

Splitting p-primary cohomology classes of tori in characteristic p

Zev Rosengarten

We prove that $p$ -primary cohomology classes of a torus $T$ over a global function field of characteristic $p$ may be split by suitable separable $p$ -primary extensions. More preci…

math.AG2025

Rigidity And Unirational Groups

Zev Rosengarten

We prove a rigidity theorem for morphisms from products of open subschemes of the projective line into solvable groups not containing a copy of $\Ga$ (for example, wound unipotent…

math.AG2025

Permawound Unipotent Groups

Zev Rosengarten

We introduce the class of permawound unipotent groups, and show that they simultaneously satisfy certain "ubiquity" and "rigidity" properties that in combination render them very u…

math.AG2025

Extensions of Abelian Schemes and the Additive Group

Gabriel Ribeiro, Zev Rosengarten

We compute extension sheaves of abelian schemes and of the additive group by the multiplicative group in the fppf topology. Our main results include a generalized and streamlined p…