Institution: | a Mark Kac Complex Systems Research Centre, Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Kraków, Poland b Fachbereich Physik, Universität Duisburg-Essen, Campus Duisburg, 47048 Duisburg, Germany c Centrum Fizyki Teoretycznej, Polska Akademia Nauk, Al. Lotników 32/44, 02-668 Warszawa, Poland |