Aut-invariant quasimorphisms on free products

Bastien Daniel Karlhofer* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Downloads (Pure)


Let G = A ∗ B be a free product of freely indecomposable groups. We explicitly construct quasimorphisms on G which are invariant with respect to all automorphisms of G. We also prove that the space of such quasimorphisms is infinite-dimensional whenever G is not the infinite dihedral group. As an application we prove that an invariant analogue of stable commutator length recently introduced by Kawasaki and Kimura is non-trivial for these groups.
Original languageEnglish
Number of pages19
JournalAnnales mathématiques du Québec
Early online date3 Dec 2021
Publication statusE-pub ahead of print - 3 Dec 2021


  • Aut-invariant
  • Quasimorphism
  • Free product
  • Stable commutator length


Dive into the research topics of 'Aut-invariant quasimorphisms on free products'. Together they form a unique fingerprint.

Cite this