arXiv subjects

Guillaume Falmagne

Publications and source records attributed to Guillaume Falmagne.

5 recordsLinked to original sources

arXiv2026

From risk to flourishing: Seeds for responding to a complex world

Flourishing is the actualization of all beings toward their good -- not only individually but collectively, answering the question of `how do we live well with and for each other?'. In science as in society, the tendency to reduce, segregate, specialize, and settle has precluded embracing the concept of flourishing as a guiding principle. We aim to identify an approach to risk science research that promotes the flourishing of socio-ecological-technological systems (SETS). We discuss the normative role of an orientation toward flourishing for the field of risk science. We explore the possibility that (risk) science could be done in a way that is capable of pointing society toward a different future, one more resilient and more capable of flourishing. Our exploration mirrors the conversational nature of flourishing itself: examine ideologies traditionally believed to be rigidly in opposition and consider what emerges in the space(s) and conversation between them. We call this a dialectical approach. Within this paradigm grounded in conversation, pluralism, and pragmatism, we revisit three longstanding tensions in risk science: physical$|$social, determinism$|$uncertainty, contextuality$|$generality. Although these tensions are not new, revisiting them together through the lens of complexity science, and with explicit attention to the normative commitments that shape risk research, reveals underexplored possibilities for the field. Examining them in conversation with the other allows us to explore the provisional seeds for what might be termed complex risk science: interdependence, responsivity, participation, pluralism, openness, and ongoingness. Enacting the dialectical paradigm towards a risk science for a flourishing world will depend on creating collectives toward complex risk science, supporting them with skillfully governed commons, and centering care in our research.

physics.soc-ph↗

arXiv2026

Interpretable Early Warnings using Machine Learning in an Online Game-experiment

Stemming from physics and later applied to other fields such as ecology, the theory of critical transitions suggests that some regime shifts are preceded by statistical early warning signals. Reddit's r/place experiment, a large-scale social game, provides a unique opportunity to test these signals consistently across thousands of subsystems undergoing critical transitions. In r/place, millions of users collaboratively created ''compositions'', or pixel-art drawings, in which transitions occur when one composition rapidly replaces another. We develop a machine-learning-based early warning system that combines the predictive power of multiple system-specific time series via gradient-boosted decision trees with memory-retaining features. Our method significantly outperforms standard early warning indicators. Trained on the 2022 r/place data, our algorithm detects half of the transitions occurring within 20 min at a false positive rate of just 3.6%. Its performance remains robust when tested on the 2023 r/place event, demonstrating generalizability across different contexts. Using SHapley Additive exPlanations (SHAP) for interpreting the predictions, we investigate the underlying drivers of warnings, which could be relevant to other complex systems, especially online social systems. We reveal an interplay of patterns preceding transitions, such as critical slowing down or speeding up, a lack of innovation or coordination, turbulent histories, and a lack of image complexity. These findings show the potential of machine learning indicators in socio-ecological systems for predicting regime shifts and understanding their dynamics.

physics.soc-ph↗

arXiv2024

Path-length dependence of parton and jet energy loss from universal scaling laws

The universal dependence of hadron suppression, $R_{\rm{AA}}(p_\perp)$, observed at large-$p_\perp$ in heavy ion collisions at RHIC and LHC allows for a systematic determination of the average parton energy loss $\langle ε\rangle$ in quark-gluon plasma (QGP). A simple relation between $\langle ε\rangle$ and the soft particle multiplicity allows for probing the dependence of parton energy loss on the medium path-length. We find that all the available measurements are consistent with $\langle ε\rangle \propto L^β$ with $β=1.02\pm^{0.09}_{0.06}$, consistent with the pQCD expectation of parton energy loss in a longitudinally expanding QGP. We then show, based on the model predictions, that the data on the azimuthal anisotropy coefficient divided by the collision eccentricity, $v_2/\rm{e}$, follows the same scaling property as $R_{\rm{AA}}$. Finally, a linear relationship between $v_2/\rm{e}$ and the logarithmic derivative of $R_{\rm{AA}}$ at large $p_\perp$ offers a purely data-driven access to the $L$ dependence of parton energy loss. Quite remarkably, both hadron and jet measurements obey this latter relationship, moreover with consistent values of $β$. This points to the same parametric path-length dependence of parton and jet energy loss in QGP.

hep-ph↗

arXiv2022

Probing the path-length dependence of parton energy loss via scaling properties in heavy ion collisions

The scaling property of large-$p_\perp$ hadron suppression, $R_{\rm{AA}}(p_\perp)$, measured in heavy ion collisions at RHIC and LHC leads to the determination of the average parton energy loss $\langle ε\rangle$ in quark-gluon plasma produced in a variety of collision systems and centrality classes. Relating $\langle ε\rangle$ to the particle multiplicity and collision geometry allows for probing the dependence of parton energy loss on the path-length $L$. We find that $\langle ε\rangle \propto L^β$ with $β=1.02^{+0.09}_{-0.06}$, consistent with the pQCD expectation of parton energy loss in a longitudinally expanding quark-gluon plasma. We then demonstrate that the azimuthal anisotropy coefficient divided by the collision eccentricity, $v_2/\textrm{e}$, follows the same scaling property as $R_{\rm{AA}}$. This scaling is observed in data, which are reproduced by the model at large $p_\perp$. Finally, a linear relationship between $v_2/\textrm{e}$ and the logarithmic derivative of $R_{\rm{AA}}$ is found and confirmed in data, offering an additional way to probe the $L$ dependence of parton energy loss using coming measurements from LHC Run 3.

hep-ph↗

arXiv2019

Quenching of hadron spectra in XeXe and PbPb collisions at the LHC

The $p_\perp$ dependence of the nuclear modification factor $R_{\text{AA}}$ measured in PbPb collisions at the LHC exhibits a universal shape, which can be very well reproduced in a simple energy loss model based on the BDMPS medium-induced gluon spectrum. We update a former study by including in the analysis the recent CMS measurements on $J/ψ$ production in PbPb collisions at $\sqrt{s}=5.02$ TeV and charged hadron production in XeXe collisions at $\sqrt{s}=5.44$ TeV. The average parton energy loss extracted from minimum bias XeXe collisions is reduced typically by 20% compared to PbPb collisions, consistent with a length dependence $\langle\barε\rangle \propto L^{1.3\pm0.5}$ with $L\propto A^{1/3}$.

hep-ph↗