Graduated and Master's degrees in History from Université de Paris VII (1975 and 1976). PhD in Social History from the University of São Paulo (1987). Emeritus Professor at Fluminense Federal University (2024). He is a Full Professor of Contemporary History at Fluminense Federal University (retired since 2016, but still active in the Master's and PhD Program in History at the same institution) and a Researcher 1A at CNPq. He served as a Visiting Professor in the Graduate Program in Arts (PPGartes) at the State University of Rio de Janeiro (2022/2024). He was also a Visiting Researcher at Stanford University, Hoover Institution (2022). He is currently developing the following research lines: Civil Wars in Russia (1918-1921) and the social and historical foundations of authoritarian socialism; Democratic alternatives defeated during the course of the Russian revolutions. The reemergence of authoritarian proposals in the context of the current digital revolution (21st century). His main research themes include: Socialist revolutions; authoritarian socialism; democratic alternatives in the Russian revolutions; and the reemergence of authoritarianism in the 21st century.