An entropy for $ℤ^2$ -actions with finite entropy generators
Tom 157 / 1998
                    
                    
                        Fundamenta Mathematicae 157 (1998), 209-220                    
                                        
                        DOI: 10.4064/fm-157-2-3-209-220                    
                                    
                                                Streszczenie
We study a definition of entropy for $ℤ^+ × ℤ^+$-actions (or $ℤ^2$-actions) due to S. Friedland. Unlike the more traditional definition, this is better suited for actions whose generators have finite entropy as single transformations. We compute its value in several examples. In particular, we settle a conjecture of Friedland [2].