When users open Google Maps or another digital map provider, they see bus stops, bike lanes, motorways. Raphael Steiner sees nodes, edges, graphs. “Graphs” here doesn’t mean the kind that depicts functions, but rather shows networks of nodes that are connected together – or not. The link between two nodes is called an edge.
Steiner’s subjects are mathematics and theoretical computer science. The offices of ETH Zurich’s Institute of Theoretical Computer Science are located on the 21st floor of the Andreasturm high-rise in Zurich’s Oerlikon quarter. A location with a fantastic view like this couldn’t be more fitting for a high-flyer like Steiner. The 23-year-old has been working at ETH Zurich for more than two years, starting as an ETH Fellow in a programme aimed at postdocs who have already demonstrated scientific excellence in the early stages of their careers. Since September 2023, he has been supported by an Ambizione grant from the Swiss National Science Foundation, which will enable him to carry out his own research project and supervise his first doctoral student for the next four years.
The mathematics of road networks
“I deal with discrete mathematics,” Steiner says. “This means the objects I study are mostly finite things.” One example is graphs, which are of particular interest to the young mathematician.
They can be used to represent a traffic network with the intersections as nodes and the roads as edges, where additional information can be stored such as the time it takes to travel a particular route. “Google Maps uses this kind of graph to find the shortest route from A to B,” Steiner explains. “So graph theory definitely has practical relevance in developing algorithms to solve problems of optimum connectivity as quickly as possible. But I focus more on theoretical issues.”
School-leaving exam and Master’s degree in the same year
Raphael Steiner became interested in mathematics as a boy growing up in the southern German town of Tuttlingen. In school, he read books on astrophysics. “That’s also when I got into relativity a little bit and realised that you need a lot of maths to understand what happens with black holes, among other things,” he says. By the time he finished primary school, he had already worked his way through all the secondary school maths textbooks. Together with his sister, who is five years older and at the time was preparing to sit her school-leaving exam (Abitur), he solved problems at this level.