Oscar Alfredo Sierra Fonseca builds a trajectory that combines technical rigor, curiosity, and openness to new paths
Originally from Colombia, postdoctoral researcher Oscar Alfredo Sierra Fonseca came to Brazil 11 years ago to pursue his master’s degree. “Research opportunities are greater here” | Image: Personal Archive
When he was still an undergraduate student at the Universidad Nacional de Colombia in Bogotá, Oscar Alfredo Sierra Fonseca discovered that equations had much more life than he imagined. They were not just symbols on a blackboard, but instruments to describe physical phenomena - sounds, waves, movements, and even predictions.
“I was always interested in how mathematics could explain the real world. Differential equations caught my attention because of the way they modeled physical phenomena,” he recalls.
This fascination led him to his first scientific project, which consisted of simulating the behavior of an acoustic tube, guided by Professor Mauricio Ruiz. After graduating, however, the Colombian reality imposed a challenge: there were no scholarships that allowed exclusive dedication to research. To continue studying, he would need to work at the same time - unless he accepted crossing borders.
The solution to this impasse was to look to Brazil, more specifically the Federal University of Rio de Janeiro (UFRJ), which held an “extramural” exam to select foreign students. The researcher was not accepted directly, but he placed first in the 2014 summer course, the year of the World Cup in Brazil.
“That guaranteed my entry into the master’s program. But I didn’t stay here during the games and ended up not watching anything, something I regret to this day,” he jokes.
Oscar is a postdoctoral researcher at FGV EMAp, under the supervision of Professor Maria Soledad Aronna | Image: Personal Archive
Academic leap: a coffee that changed everything
At UFRJ, under the supervision of Professor Ademir Pazoto, Oscar dove into more complex wave equations, such as KdV and BBM. “You have a system, the initial data, and the desired final state. The problem is finding how to intervene in the system so it reaches the final state with the smallest possible error. That is controllability,” he explains.
During his PhD, he wrote four articles that became decisive for the next step in his career. And it was precisely the sum of this work that caught the attention of Professor Maria Soledad Aronna, from the School of Applied Mathematics at the Getulio Vargas Foundation (FGV EMAp).
The opportunity to do a postdoc at FGV EMAp arose unexpectedly, like many good academic stories.
“I was having coffee with a former advisor at UFRJ when a professor mentioned that FGV EMAp would open a position. I barely knew FGV, but my advisor encouraged me: ‘It’s very good, you should try.’ We wrote the cover letter together, I sent it, and I was called for an interview,” Oscar says.
The committee consisted of Soledad Aronna and Professor Yuri Saporito. Their questions were about his work, expectations, and future plans. Shortly afterward, the result came: approved.
Still in his first year at FGV EMAp, Oscar and Soledad submitted a proposal to the “Postdoctoral Nota 10” call from the Rio de Janeiro State Research Support Foundation (FAPERJ), one of the main scientific funding agencies in the country. The initiative is aimed exclusively at researchers with excellent academic output and scientific leadership potential, and it is among the most competitive and prestigious grants offered by the institution.
The project was approved, guaranteeing funding for up to four years of research on high-impact topics in the area of control and optimization. For Professor Maria Soledad Aronna, the achievement had special significance. “The FAPERJ Nota 10 Postdoctoral Fellowship is highly competitive and recognized. It was the first time FGV EMAp received this type of support, but it certainly won’t be the last. This demonstrates the researcher’s qualities, his commitment, and dedication,” she says.
At the institution, Oscar develops research in the area of Optimal Control, more precisely problems governed by randomized differential equations, that is, equations that depend on a stochastic parameter.
“It is a recent formulation that arises directly from applications, especially in models whose parameters are known only through probability distributions,” explains the FGV EMAp professor.
The researchers have already published two articles: one in the international journal ESAIM - Control, Optimisation and Calculus of Variations, in collaboration with Michele Palladino from the University of L’Aquila, Italy, and another in Set-Valued and Variational Analysis with Gabriel Monteiro, a PhD student at FGV EMAp. In addition, a third article is about to be published in the Proceedings of the IEEE Control and Decision Conference. “This work addresses Hamilton–Jacobi-type problems and shows that the value function associated with them is precisely the solution to the partial differential equation of the same name. It was the article that consumed the most of my time during the postdoc, developed in partnership with Professor Soledad and Professor Michele Palladino from Italy. The process was long, full of back-and-forth, until it was finally accepted, and I hope it will be published later this year,” Oscar says.
Encouraged by Soledad, Oscar has actively participated in international conferences, where he presents recent results from the research conducted at FGV EMAp. He also highlights the School’s financial support, which makes it possible for researchers to attend events abroad, as well as the internal dynamics of seminars and scientific meetings, which are essential for expanding dialogue and opening new avenues of collaboration.
“She encouraged me a lot to show myself to the international community. Participating in these events gives visibility, opens doors to new partnerships, and allows the world to know that we are here, researching and producing,” he says.
In 2024, Oscar presented at CNMAC an article that explains how decision problems with uncertainties can be modeled and solved through dynamic programming principles | Image: Personal Archive
Having lived in Brazil for 11 years, Oscar already feels at home. Despite the initial difficulty with the language, he has now mastered it and, when he goes to Colombia to visit his family, he ends up slipping Portuguese words into the conversation. The researcher is a football fan, and after many trips to Maracanã Stadium, he became a Flamengo supporter. To unwind, Oscar enjoys running along the Rio beaches, sometimes even wearing the Rio team’s jersey. Because of the connections he has built here, he hopes to stay and become a university professor.
“Latin America is advancing in Applied Mathematics, and much of this movement comes from the momentum driven by Brazil. I see many connections being made, especially in studies of epidemiological problems, such as dengue. I feel that I can contribute a lot to this development,” he concludes.
The researcher participated in the Summer School and Workshop on Modeling and Numerical Methods in Epidemiology, in Cali | Image: Personal Archive