Eleftherios Papantonopoulos is Emeritus Professor in the Physics Department of the National Technical University of Athens. His research interests include the study of Lie Algebras and their applications to elementary particles phenomenology; applications of the AdS/CFT correspondence to Condensed Matter Physics; studies of Relativity and Cosmology in Supergravity and String theories; study of Black Hole solutions, their perturbations and construction of cosmological models in Modified Gravity Theories; Gravitational collapse and Gravitational Waves. For more than 20 years he has organized the biennial Aegean Summer School for postgraduate students and young researchers. Mavromatos Nikolaos is Professor of Physics at Kings College London. His research interests include Astro-particle Physics; Quantum Gravity and Dirichlet-Brane Phenomenology; Strings and Conformal Field Theory; Yang-Mills Gauge Theory; Low-dimensional gauge field theories and Supersymmetry; interdisciplinary research between Condensed Matter and Particle Physics.