7 citations · 18 across the 14 of their papers we have counts for
18 papers
Algebraicity and smoothness of fixed point stacks
Matthieu Romagny
We study algebraicity and smoothness of fixed point stacks for flat group schemes which have a finite composition series whose factors are either reductive or proper, flat, finitel…
Fixed point stacks under groups of multiplicative type
Matthieu Romagny
We prove that if a group scheme of multiplicative type acts on an algebraic stack with affine, finitely presented diagonal then the stack of fixed points is algebraic. For this, we…
Néron blowups and low-degree cohomological applications
Arnaud Mayeux, Timo Richarz, Matthieu Romagny
We define dilatations of general schemes and study their basic properties. Dilatations of group schemes are -- in favorable cases -- again group schemes, called Néron blowups. We g…
Unramified F-divided objects and the étale fundamental pro-groupoid in positive characteristic
Yuliang Huang, Giulio Orecchia, Matthieu Romagny
Fix a scheme of characteristic . Let be an -algebraic stack and let $\mbox{Fdiv}(\mathscr{M})$ be the stack of $\mbox{F}$-divided objects, that is sequences…
Representations of Affine Group Schemes Over General Rings
Giulia Battiston, Matthieu Romagny
Among all affine, flat, finitely presented group schemes, we focus on those that are pure, this includes all groups which are extensions of a finite locally free group by a group w…
Smooth affine group schemes over the dual numbers
Matthieu Romagny, Dajano Tossici
We provide an equivalence between the category of affine, smooth group schemes over the ring of generalized dual numbers , and the category of extensions of the form $1 \righ…