Non-commutative Barge-Ghys quasimorphisms: an erratum

Abstract

This is an erratum to the paper ``Non-commutative Barge-Ghys quasimorphisms''. The effective version of Ambrose-Singer theorem used in this paper was mis-stated, making Theorem 3.11 false as stated. However, this statement remains true for a semidirect product $G=A\rtimes K$ of a non-compact Lie group with a compact Lie group $K$, as long as the curvature of the connection belongs to the Lie algebra of $K$. Theorems 3.12 and 3.22 remain true under this assumptions, the statements of Theorems 4.28 and 4.31 are modified accordingly. Theorem 5.2 is valid only for compact Lie groups.