Marc Barthelemy is a French theoretical physicist at the Institute of Theoretical Physics (IPhT) in Paris-Saclay (CEA/CNRS). He worked on complex and spatial networks, theoretical epidemiology, and urban dynamics. His work addresses issues at the intersection of physics and various disciplines such as geography, urban planning, epidemiology, and demography. By leveraging tools and concepts from statistical physics, he has analyzed empirical data and modeled diverse systems, tackling crucial challenges such as virus propagation, mobility and congestion in cities, the historical evolution of infrastructures, and the dynamics of urban populations. Marc Barthelemy is known for his studies on spatial networks and infrastructures, the structure of cities, transportation systems, and the urban population evolution and Zipf's law. The city growth equation reveals that urban population evolution is governed by a stochastic model incorporating two types of fluctuations: those related to interurban migrations and those due to natural growth. Source: Wikipedia (en)