ès sciences, mention interdisciplinaire par Olga Chekeres Thèse No. 5336 GENÈVE Atelier d'impression ReproMail de l'Université de Genève 2019 My deepest gratitude is to my advisor Anton Alekseev. He is standing behind my every step into the wild of mathematical physics, and no words are ever going to be enough to thank him for all his guidance and support, patience and wise advice, encouragement when needed, being kind, inspiring and available. I would also like to express my gratitude • to my

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... hildren, for non-stop motivation, 7/7 and 24/24; • to my parents, who taught me to value education above everything; • to all my friends and to the inhabitants of Villa Battelle Math Department in Geneva for bringing so much inspiration, fun and joy into my work and life; • to God 1 for playing dice, so much in my favour.