It has been a long way. Only by His grace, I'm here finishing this step, with my heart full of gratitude. I thank to my wife, Rebeca, for her love and support in the good and bad moments. It is our achievement. Also I thank my parents, Ricardo and Delza, for being so present in my life. Thank you for all dedication to your children. This moment is a result of such dedication. I thank my brother, William, for all the support and complicity. I wouldn't have done it without you.I thank my family -Jesana, Tiago, Isabella, and Manuella -for all the moments together. With you, my life is happier. I want to say thank you to Hélio, my advisor, for counselling me along these years, and for teaching me many lessons. Also I thank Abelardo Barreto and Guilherme Schardong who worked with me in this project, from theoretical discussions to code implementation. I thank my laboratory friends for the discussions, the friendship, and for making the laboratory a place I loved to be. Also I thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for the scholarship. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brasil (CAPES) -Finance Code 001.