Topological and algebraic definitions of commutator lengths. Topological and group theoretic definitions of stable commutator length. Bavard duality and applications of stable commutator length to bounded cohomology.
Links:
[1] http://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/de/node/3444
[3] http://www.mpim-bonn.mpg.de/de/node/2761