Analysis of economic activities during a century of urban growth in Paris Evolution between 1829 and 1907 of the spatial distribution of cafes and restaurants in Paris. Researchers Marc Barthelemy (Institut de Physique Théorique and Centre d'Analyse et de Mathématique Sociales, EHESS), and Julie Gravier (Centre de Recherches Historiques and Centre d'Analyse et de Mathématique Sociales, EHESS) have just published in the prestigious journal Nature cities [1] their findings on the analysis of economic activities in a century of urban growth in the city of Paris.

Contemporary studies on the dynamics of economic activity in growing cities generally focus on periods of a few years or a few decades. Using a recently constructed geohistorical database containing around 1 million entries from historical directories, this study presents a detailed analysis of economic activities in Paris over almost a century (1829-1907).

The authors show that activities can be classified into three categories according to their dynamics and their scaling law in relation to population: (1) linear for everyday needs such as food and healthcare, (2) sublinear for public services such as education and administration, and (3) superlinear for specialized or temporary trends. The study also shows that these activities are highly sensitive to historical events, such as major public works or political conflicts, offering new insights into the evolution of activities in growing cities.

[1] Julie Gravier et Marc Barthelemy, A typology of activities over a century of urban growth, Nature Cities 1, pages 567–575 (2024)

Jorge graduated in Theoretical Physics from the University of Havana (UH), Cuba. He then joined the Center of Molecular Immunology in Havana, a biopharmaceutical institution that develops therapeutic drugs for cancer and autoimmune diseases. He completed his Ph.D. on mathematical models of cellular metabolism in culture, visiting the Beatson Cancer Research Institute (Glasgow, UK) and the Politecnico di Torino (Italy).

Jorge then moved to Paris for a postdoctoral fellowship at ENS, where he worked on the statistical physics of unsupervised representation learning and applications to biological sequences. He was also awarded a PSL Junior Fellowship in Artificial Intelligence. He joins the IPhT on a CNRS "Junior Chair".

Welcome to the IPhT, Jorge!

Carlo Heissenberg graduated with flying colors in 2019 from the Scuola Normale Superiore di Pisa, the Italian twin sister of the Ecole Normale de Paris. His initial research focused on the infrared properties of gravitational theories and higher spin theories from the perspective of asymptotic symmetries, a topic that later found phenomenological applications in the context of gravitational wave studies.

It was during his first postdoctoral period at Nordita-Uppsala (2019-2023) that Carlo started working on gravitational wave physics using ideas borrowed from particle physics, such as scattering amplitudes and eikonal exponentiation in particular. He quickly became a leader in the field, publishing several important papers with world-famous physicists such as Gabriele Veneziano. Carlo's group achieved, for instance, the first complete calculation of the gravitational deflection angle to the third post-Minkowskian order in the Newton coupling constant expansion, while simultaneously resolving the high-energy limit problem that was puzzling the community.

In the meantime, Carlo was granted a Marie-Curie fellowship and moved to his second postdoc at Queen Mary, while continuing to work on gravitational wave physics, focusing on new observables (waveforms, angular momentum loss, effect of spins…) that could be calculated efficiently using scattering amplitudes techniques.

Carlo accepted an offer from the IPhT and will join the lab as a permanent member in Fall 2024.