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AgradecimentosThe best part of the thesis is here, since I can write about the people who I can thank a lot, the good moments of my Ph. D., and add anything that, in the future, when someone opens this part, he or she will see that I am grateful for these wonderful four years.First I thank my supervisors, Aernout and Rodrigo, and my cosupervisor, Daniel, to open the door of statistical mechanics. Thanks to you, I found the area that I will hopefully follow for the rest of my life. I started studying this area when I was in the master degree, and Rodrigo gave a lecture on the introduction of models for ferromagnetism. He showed for the students that the statistical mechanics is not a rocket science, and it is actually a nice area. Thanks Rodrigo to give this amazing lecture. Aernout, who showed me that it is possible to think in the qualitative ideas avoiding heavy maths to understand how a problem could be solved, opened my mind. Thanks for many discussions that we had in Groningen. Daniel, I would like to thank you to have nice discussions about the spatial Gibbs random graphs problem, because those discussions were fruitful to understand how an idea and a proof can be simplified. Thanks to many advices and to help me how to "survive" in Groningen.I would like to thank Noga Alon, Arnaud Le Ny and Wioletta Ruzsel to show me that to do research with collaborations is very interesting and delightful.Let me thank Irene, who rented a room for me when I was in Groningen. The room is very confortable, and it was very important for me, since I could say "I'm home" in a country where I have never been before. Thanks to show me many dutch cultures, to help me to solve many bureaucracies, to teach dutch language, and for the dinners. Dank u wel, het was gezellig! Why not also thanks Groningen city? Het is een mooie stad. Ik ben elke dag gefietst en ik altijd vond culturele evenementen. Ik vind Groningen leuk! Dank u wel, Groningen.There are many people to thanks when I lived in the Netherlands. First, I would like to thank all of the group of the Groningen university. Desiree, Ineke and Lineke to help me for the university bureaucracy. Pedro, it was very fun to talk a lot with you, let's go again to eat krokketjes and drink dutch beer. Réka, it was so nice to show me nice places in Groningen and invite me to watch nice movies. Vladimír, thanks a lot to invite me to the game party and pancakes evenings. Further I would like to thanks Mónika, Nikolay, Pan and all other former and present members of our group.I would like to thanks Sylvia and Sonia for many nice talks that we had.Bruno, you are brazilian, we met in Brazil, but it is so nice that we both went to the Netherlands at the same time to do our Ph. D. Thanks to show me Delft and the research group. Let's spread the brazilian's culture and memes in the world! Ric...