Centre de Recerca Matemàtica, Campus de Bellaterra Edifici C, 08193 Bellaterra, Barcelona, Spain.|School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2QL, United Kingdom.|Center for Brain and Cognition, Department of Information and Communication Technologies, Universitat Pompeu Fabra, C. Ramon Trias Fargas 25 - 27, 08005 Barcelona, Spain.|Centre de Recerca Matemàtica, Campus de Bellaterra Edifici C, 08193 Bellaterra, Barcelona, Spain.