Boundary maps in bounded cohomology Appendix to: Burger and Monod, in this issue (Q1606088)

In this appendix to the paper by \textit{M. Burger} and \textit{N. Monod} [ibid. 12, 219-280 (2002; see the preceding review)], the authors show that given a group homomorphism \(\pi:G_1\to G_2\), there is a contravariant map \(\pi^*:H^*_{cb} (G_2)\to H^*_{cb} (G_1)\) of continuous bounded cohomology groups. This contravariance property is far from being obvious, and the proof uses properties of boundary maps.