4 papers
Small G-varieties
Hanspeter Kraft, Andriy Regeta, Susanna Zimmermann
An affine varieties with an action of a semisimple group is called "small" if every non-trivial -orbit in is isomorphic to the orbit of a highest weight vector. Such a v…
Continuous automorphisms of Cremona groups
Christian Urech, Susanna Zimmermann
We show that if a group automorphism of a Cremona group of arbitrary rank is also a homeomorphism with respect to either the Zariski or the Euclidean topology, then it is inner up…
A new presentation of the plane Cremona group
Christian Urech, Susanna Zimmermann
We give a presentation of the plane Cremona group over an algebraically closed field with respect to the generators given by the Theorem of Noether and Castelnuovo. This presentati…
The decomposition groups of plane conics and plane rational cubics
Tom Ducat, Isac Hedén, Susanna Zimmermann
The decomposition group of an irreducible plane curve is the subgroup of birational maps which restrict to a…