The real plane Cremona group is a non-trivial amalgam

Abstract

We show that the real Cremona group of the plane is a non-trivial amalgam of two groups amalgamated along their intersection and give an alternative proof of its abelianisation.

References in corpus (2)

• Subgroups of odd order in the real plane Cremona group
• Signature morphisms from the Cremona group over a non-closed field