G. Prof, . Meylan, . A. Prof, . Kusenko, A. Prof et al., All my gratitude goes to Prof M. Shaposhnikov for his essential role in this work. I would like to thank all the members of Jury Maggiore for taking part to this. I have to give many thanks to D. Moore, M. Ruiz-Altaba, for their usefull help and discussions to K. Zuleta for her help, it can not be over without mentionning M. Giovaninni, T Ghergeta whose discussions were always very interesting. I also think to those who helped me with their support, Alexis Reynaud, my parents and all my friends and Charly my lovely pet, Acknowledgments First the author would like to thank Doris for her essential support

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