Ulysse Marquis

... a foundation for robust growth models —
and raises questions about the physics of anisotropic, intrisically anomalous interfaces, which exhibit unusual phenomenolgy w.r.t known universality classes.

Studies of the radius fluctuations reveal that the tails are described by a stretched exponential, with exponent ~1/2. These findings help understanding the scaling of higher-order moments of the roughness.

Our results provide the first empirical laws of urban sprawl dynamics, offering ..

widely from a city to another. This variability reflects 1) the quenched nature of the landscape 2) the combination of different growth mechanisms 3) endogeneous anisotropic effects.

The physics of surface growth offer a toolbox to study the dynamics of roughening surfaces, through observables (width, radius-radius correlation...), scaling ansatzes and universality classes. We found an universal exponent ruling the local roughness, while the growth and dynamic exponents change

We find that demographic pressure (g) does not only control growth speed, but also the growth mechanism. At small g, local growth controls the development, while at high values of g (typically, higher than 10^-2), coalescence drives city growth (which have different geometric signatures).

The aggregate built-up area grows roughly affinely with respect to the population, but we observe density-breaking points separating various phases of developments. Despite this, the growth is anisotropuc : the exponents characterizing directional radii growth vary largely around the expected 1/2.

Using fine-grained satellite maps embedded in polar coordinates, we characterized how cities expand as their populations grow.
See here the growth of Changzhou (China) between 1985 and 2015.

Our work on the dynamics of urban expansion just got published in the Physical Review Letters ! journals.aps.org/prl/abstract...

When is better to think without words? Non-verbal, blurry thinking is faster and can search in a broader way, but it is more error-prone than verbal thought.

"In the 1940s, when the French mathematician Jacques Hadamard asked good mathematicians how they came up with solutions to hard problems, they nearly universally answered that they didn’t think in words; neither did they think in images or equations" www.henrikkarlsson.xyz/p/wordless-t...

Principled Model Selection for Stochastic Dynamics link.aps.org/doi/10.1103/...

Modeling the spatial growth of cities
https://arxiv.org/abs/2510.03045

Universal Model of Urban Street Networks
https://arxiv.org/abs/2509.21931

Shortest-path percolation on scale-free networks The shortest-path percolation (SPP) model aims at describing the consumption, and eventual exhaustion, of a network's resources. Starting from a graph containing a macroscopic connected component, ran...

Strikingly, the shortest-path percolation homogenizes scale-free networks before the phase transition, resulting in the same universality class as the Erdős–Rényi Networks!

Check out our new preprint on arXiv: arxiv.org/abs/2509.09142

From lines to networks
https://arxiv.org/abs/2509.07951

Looks more complicated than it is. In our recent study journals.plos.org/plosone/arti... we search for an optimum city size, minimizing both urban carbon emissions and urban heat island (constraint: fundamental allometry). It turns out that given the known UHI parameters such optimum does not exist.

Wide coverage of social media and disinformation analysis yesterday from our lab at the @css-conference.bsky.social, with four talks presenting our works associate to the European projects #AI4TRUST #AICODE_EU #HATEDEMICS

Also seen yesterday at @css-conference.bsky.social a work on reinforcement learning applied to ants behaviour by Alessio Pitteri, our study of the historical evolution of EU projects by @verorsanigo.bsky.social and the study on Coordinated Behavior by @elisamurators.bsky.social #CCS2025

commercial spaces are organized across a city.

these patterns naturally come from clusters of places that share similar activity levels, even if they’re not next to each other. By connecting what happens locally to the bigger city-size distribution—both analytically and empirically—we show how power-law patterns can emerge in the way ...

New pre-print out ! Work led by @eleandre.bsky.social, in collaboration with M. Napolitano and @ricgallotti.bsky.social. Using Foursquare data from Bologna, we find that the distribution of POIs follows a clear power-law pattern at the city scale. To explain this, we introduce a framework where ...

Scale-free Points-of-Interest Distribution in a City Emerging from Homogeneous Poissonian-point Processes
https://arxiv.org/abs/2509.01699

Yesterday was our first day at @css-conference.bsky.social
in Siena 🇮🇹. We presented on Telegram data collection @elisamurators.bsky.social , city growth @ulyssemarquis.bsky.social and urban traffic (Alberto Amaduzzi). Excited for 5 more talks today! #CCS2025

Epidemiology models explain rumour spreading during France’s Great Fear of 1789 - Nature Epidemiological methods are used to show that the Great Fear of 1789, a series of peasant insurrections in rural revolutionary France, was driven by deliberate political action rather than spontaneous...

Very interesting study on social contagion applied in a historical context by @szapperi.bsky.social and collaborators. Powerful example of where good historical data can lead us in the future.

www.nature.com/articles/s41...

Pour ce que ça vaut, je recopie ci-dessous un fil que j'ai posté sur Twitter en 2022, où je tente de raconter les bases fondamentales de la thermodynamique à tout le monde, d'une manière que j'espère pédagogique. 🧵⤵️ •1/24

Opinion dynamics: Statistical physics and beyond Opinion dynamics, the study of how individual beliefs and collective public opinion evolve, is a fertile domain for applying statistical physics to complex social phenomena. Like physical systems, soc...

Opinion dynamics: Statistical physics and beyond

arxiv.org/abs/2507.11521

Geometric Criticality in Scale-Invariant Networks
https://arxiv.org/abs/2507.11348

When dialects collide: how socioeconomic mixing affects language use - EPJ Data Science The socioeconomic background of people and how they use standard forms of language are not independent, as demonstrated in various sociolinguistic studies. However, the extent to which these correlati...

When dialects collide: how socioeconomic mixing affects language use epjdatascience.springeropen.com/articles/10....

So excited to see this come together! 🎉

Our latest study explores the interplay between science and misinformation in public debates during COVID-19 🔍 arxiv.org/abs/2507.01481

👇Take a look

Phys. Rep.: Introduction to correlation networks: Interdisciplinary approaches beyond thresholding
https://www.sciencedirect.com/science/article/pii/S0370157325001784?dgcid=rss_sd_all

Why Do We Build Cities in the Sky? - Skynomics Blog Jason M. Barr May 7, 2024 On May 14, my book Cities in the Sky: The Quest to Build the World’s Tallest Building was released by Scribner Books. You can order a copy and sign up for my email list here....

#Skyscrapers remain controversial, yet the continue to be built world over? Why do we build #cities in the sky?
buildingtheskyline.org/cities-in-th...