- A: allometric properties on the structure of a gorgonian, from PySkelWays repo
- B: Money circuit in a 3-sector economy using CHIMES library
- C: Causal scheme of an Economy-Decarbonation-Climate model using CHIMES library
- D: Physical stock-flow circuits for a multisectoral model.
- E: iterative improvement scheme for a modular economic model.
- F: Stabilisation trajectory of an Out-of-equilibrium model using CHIMES library.
- G-H: Stochastic dynamics and agent-based model, using CHIMES library
- Who am I?
- Post-doctoral Researcher at the Environmental Justice Program, Georgetown University
- Previous Work
- Links
Table of contents generated with markdown-toc
In a few words, my passion is the study of self-organizing systems: how a few simple processes put together can allow the emergence of complex behaviors, shapes, and harmonies. I started with a focus on shapes in nature (how does a tree get its shape ? Why are waves different, and can we read the reef shape from theirs ?), and then I studied how the environment influences the shapes of biological systems and the properties emerging from this interaction: synergies, adaptation and sometimes crises.
I was lucky enough to do a Ph.D. about the beautiful shape of a coral Gorgonia ventalina, described below. The goal was to understand how such shape appears (which processes) and if the environmental influence was smartly shaping the shape: the coral would be adapted to its environment. I focused on the mechanical environment: the soft coral is bent with the waves and uses this movement to stand up and catch light and particles. That leads to impressive links between many systems like cities, butterfly wings, gorgonians, the internet, academic hierarchy, trees, continents, beams... As well as a new method to look at complex shapes, read them, and measure their properties.
Alerted by the biodiversity threat of the Anthropocene and our impacts on our society, particularly the bleak future of corals in the XXI century, I decided to study economic structure organization rules and their interaction with the environment. Society as an organism, as a dissipative structure.
Today, I develop methodologies, models, and numerical tools and prove analytical properties to understand and couple complex systems, particularly for ecological economic issues. You'll find here many elements to do so.
My goal is that 50 years from now, some young crazy students can spend years studying the beauty of our environment. That would require that a beautiful environment exists and that society is well enough to explore such non-conventional subjects.
You can always message me; I'll send you the PDF!
I recommend you this article if you want to create economic models that evolves with their physical environment, to construct a core, expand it, and understand its properties.
This article introduces a comprehensive model that encapsulates capital's physical and economic nature, addressing the complex interplay of ecological, economic, and societal dynamics and an ensemble of extensions with their effects. Emphasizing self-organization between capital investment and its services, the framework, we present relies on a double stock-flow consistency, metabolic processes, and behavioral heuristics. We demonstrate its robustness as a foundation with a justification for each hypothesis choice, encompassing dynamics related to debt and inventory. The core dynamics emerge as closed cycles between employment and wage share that align with an extended (Goodwin, 1967) model. We discuss the interest of such self-organizing approaches for the challenge of post-growth studies: in a deteriorating environment, the economic system adapts wages to maintain consistent mean growth and employment. We systematically explore how parameter variation and hypothesis substitution impacts system equilibrium position and stability, for a total of 25 complementary phenomena that we describe and mathematically analyze. It includes elasticity of substitution, endogenous technical progress, delayed dynamics on capital or wage negotiation, increasing return to scale, cost-pushed inflation, and growth- relaxing dividends. We show that, even in its two-dimensional form, the system can exhibit limit cycles with an unstable equilibrium. We conclude that an out-of-equilibrium, process-based perspective is essential, advocating for a closed cycle dynamical core as an initial framework for clarity, quantitative, coupling studies. Furthermore, we discuss the potential for extending this archetype with disaggregation to address dynamics related to inequality and multisectoral productive capital in a changing world
I recommend you this article if you want a critics of some previous IAM structure and the potential coupling possibilities with intermediate complexity climate models
Designing policy for global warming requires an integrated analysis of the interplay between the economy and the environment. The consensus is growing that, despite their dominance in the economics literature and their influence in public discussion and policymaking, the methodology employed so far by most Integrated Assessment Models ``rests on flawed foundations''. This is particularly worrisome in the face of the immense risks and challenges of global warming and the radical changes in our economies that an effective response requires. This paper introduces an alternative paradigm, {\sc idee} (Integrated Dynamic Environment-Economy), based on coupling a medium-size climate model with nonlinear, out-of-equilibrium, stock-flow-consistent macroeconomic dynamics in continuous time. {\sc idee} allows for multiple economic steady states, endogenous business cycles, endogenous growth, corporate default, and the short- and long-run assessment of various mitigation and adaptation policies. This approach is suitable for providing insights into managing the transition to net-zero emissions and coping with damages induced by the ecological crisis.
Stock-Flow-Consistent Macroeconomic Dynamics in Continuous Time (Chapter for the Routledge Handbook of Complexity Economics)
Plan of the chapter:
1 Introduction 2
2 Methodological Preliminaries 3
2.1 The Importance of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Stock-Flow Consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 On Microeconomic Foundations of Modern Macroeconomics . . . . . . . . . . . . . . 6
2.4 A Key Element, the short-run Phillips Curve . . . . . . . . . . . . . . . . . . . . . . 7
3 The Basic Framework 8
3.1 Leontief Technology: The Goodwin Model . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 CES Technology: The Van der Ploeg Model . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Corporate Debt: The Keen Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4 Empirical and Theoretical Support for Predator-Prey Models . . . . . . . . . . . . . 13
4 First Extensions 15
4.1 Inventories and Inflation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Income Inequalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3 Oligopoly Pricing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.4 Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.4.1 Damage Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.4.2 Integrated Dynamic Environment-Economy (IDEE) Models . . . . . . . . . . 20
5 Dynamics of Material Flows 22
5.1 Why Energy Matters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2 The Economy as a Dissipative Structure . . . . . . . . . . . . . . . . . . . . . . . . . 23
6 Multisectoral Dynamics 24
6.1 From One-Commodity Economies to Multisectorality . . . . . . . . . . . . . . . . . . 24
6.2 The Cambridge Controversy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6.3 Intersectoral dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7 Conclusion 28
The library is not public yet but should be in the following months. If you want to know more about it and beta-test it, don't hesitate to get in touch with me
- Do You want to explore, couple, analyze existing models, or create your own? CHIMES is the library made for you!
- Do You work with Agent-Based models (collective behavior, economic agents, bird movements), chaotic systems, spatial properties (PDE, gravitation system, climate), and multiple circuits of resources (Money, CHNOPS...) then CHIMES is the library for you!
- Do You want to do a lot of runs in parallel to test the sensitivity of a parameter or initial condition? Same!
- Do You want a user-friendly interface so that you do not code too much while keeping the full flexibility of Python at every step? Same!
- Do You want to explore a vast library of models with their demos and behavior exploration?
- Do You like Python for its practicality, but it's slow to solve equations? CHIMES is the library for you!
Some illustrations of CHIMES content
A model causal network as generated by CHIMES
E-CHIMES is the state-of-the-art self-organized macroeconomic core designed to couple any number of economic sectors and endogenize their properties (environmental coupling, government dynamics, shocks...). It fully represents the physical exchanges in an economy, from which the economic supply-use tables or Input-output can be generated.
Physical and nominal circuits
The core is only a small number of equations and will provide a closed trajectory in phase space; it is very practical to identify the impact of endogenizations on it and understand how it is structured. To create the core, one has to disaggregate the model CHI Capital-Human instabilities (see above).
ECHIMES is the production disaggregation of the fundamental structure on which the rest can be built
Ph.D. in interdisciplinary physics: self-organization of macroscopic organisms in their mechanical environment
- "form, formation, deformation of G. ventalina"
- Under the direction of Stephane Douady (MSC Paris VII) and Pascal-Jean Lopez (MNHN)
- Ph.D. defense can be found here
- Ph.D. Manuscript can be found here
PySkelWays is a python library of image analysis, network extraction, hyper-graph construction and hyper-graph analysis. It has been created to study 2D reticulated spatial networks, and can be used on various subjects (Gorgonians, cracks patterns, leaves, dragonfly wings, cities network, jellyfishes, hyphal growth...)
Link to the repository I am rewriting the core for an interfaced, updated version including extensions from Selene Jeammet, please get in touch with me if you need more
How can we read the complex shape of corals ? What are its geometrical and mechanical properties ? What can they tell us about their environment ? How do they appear, how can we decompose the shape as an ensemble of simple growth processes coupled together ? What does those growth processes tell us about the ability of Gorgonia ventalina to acclimate its environment ?
- Under the direction of Julien Derr (MSC Paris VII)
Shape creation and control are important topics for both applied development and fundamental research. We focus here on diatoms, a type of unicellular algae which create beautiful, diverse, and well regulated shells of silicate with no waste nor much energy, at the micrometer scale. The basic mechanism of diatom morphogenesis has been clearly identified, but no biologically coherent model can account for observed characteristics. After a review of known diatoms morphogenesis models and usual morphogenesis theoretical approaches in general, we present our model and its hypotheses, based on boundary conditions and movements. We then develop our numerical approach with a new code structure using finite elements, and finish with the qualitative results we obtained during this internship, thus giving a good overall view of regulation mechanisms, their impact.
Zoom on diatom shapes, showing a super-ellispe macroscopic shape and a reticulated local pattern created by calcium sillicate accretion
Left : principle of the model's dynamics. Right : Example of simulation
Link to the repository :
- Under the direction of Stephane Laffite (CEA-DAM)
Inertial Confinement Fusion (ICF) is a method of achieving nuclear fusion, a process that powers the sun and other stars, by compressing and heating a small target of fuel to extremely high temperatures and pressures. The primary goal of ICF research is to create controlled, sustainable fusion reactions that release a large amount of energy, which can potentially provide a clean and virtually limitless source of power for various applications. Those experiments create extreme conditions that mix many branches of physics and are thus hard to understand. Most approaches rely on heavy computer simulation, and while they give accurate results they do not necessarily bring comprehension. My work has been to create a simple, highly reduced model, that could explain what properties and issues were central to tackle in the quest for fusion. Based on geometrical criteria, then on instability propagation and simple fluid mechanics properties, we show the link between initial heterogeneity and the compressed deformation of a target. We identify in a very simple numerical run the amount of orthoradial kinetic energy, which determines the efficiency of a fusion target.
- Under the direction of Denis Morichon (SIAME)
We sometimes observe in geological sampling an unexpected layer of marine elements, far inland and not linked to anything else. It has been proven that those are markers of tsunamis, and their potential erosion and transport effects can dramatically impact any structure made to resist currents. It has been observed that under certain wave conditions, the pressure can transform a layer of ground into a liquified bed, changing the erosion effects and the wave dynamics. What are the conditions for such conditions to happen? What waves can generate such conditions, and where is it in the surf zone? What erosion patterns will it create? We investigate those properties through simple models and numerical 2D modelling.
Criteria of sediment transport during a run-up/washdown event with a tsunami-type wave.
