12 results on '"Romain Ducasse"'
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2. Influence of the geometry on a field-road model: the case of a conical field.
- Author
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Romain Ducasse
- Published
- 2018
- Full Text
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3. Correction to: Second order local minimal-time mean field games
- Author
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Romain Ducasse, Guilherme Mazanti, and Filippo Santambrogio
- Subjects
Applied Mathematics ,Analysis - Published
- 2022
4. A cross-diffusion system obtained via (convex) relaxation in the JKO scheme
- Author
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Romain Ducasse, Filippo Santambrogio, and Havva Yoldaş
- Subjects
Mathematics - Analysis of PDEs ,35A01, 35A15, 49J45 ,Applied Mathematics ,FOS: Mathematics ,Analysis ,Analysis of PDEs (math.AP) - Abstract
In this paper, we start from a very natural system of cross-diffusion equations, which can be seen as a gradient flow for the Wasserstein distance of a certain functional. Unfortunately, the cross-diffusion system is not well-posed, as a consequence of the fact that the underlying functional is not lower semi-continuous. We then consider the relaxation of the functional, and prove existence of a solution in a suitable sense for the gradient flow of (the relaxed functional). This gradient flow has also a cross-diffusion structure, but the mixture between two different regimes, that are determined by the relaxation, makes this study non-trivial., Comment: 38 pages, 2 figures, accepted version with minor revisions
- Published
- 2021
- Full Text
- View/download PDF
5. Second order local minimal-time Mean Field Games
- Author
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Romain Ducasse, Guilherme Mazanti, Filippo Santambrogio, Institut Camille Jordan [Villeurbanne] (ICJ), Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon, Institut Polytechnique des Sciences Avancées (IPSA), Dynamical Interconnected Systems in COmplex Environments (DISCO), Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire des signaux et systèmes (L2S), CentraleSupélec-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-CentraleSupélec-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Public grant as part of the ``Investissement d'avenir' project, reference ANR-11-LABX-0056-LMH, LabEx LMH, PGMO project VarPDEMFG., French IDEXLYON project Impulsion ``Optimal Transport and Congestion Games' PFI 19IA106udl., Hadamard Mathematics LabEx (LMH), grant number ANR-11-LABX-0056-LMH in the ``Investissement d'avenir' project., ANR-16-CE40-0015,MFG,Jeux Champs Moyen(2016), Laboratoire Jacques-Louis Lions (LJLL (UMR_7598)), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire des signaux et systèmes (L2S), CentraleSupélec-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université Jean Monnet [Saint-Étienne] (UJM)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Camille Jordan (ICJ), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Modélisation mathématique, calcul scientifique (MMCS), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Lyon (ECL), and ANR-11-LABX-0056,LMH,LabEx Mathématique Hadamard(2011)
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parabolic PDEs ,congestion games ,Applied Mathematics ,MFG system ,35Q89, 35K40, 35B40, 35A01, 35D30 ,Mean Field Games ,Mathematics - Analysis of PDEs ,existence of solutions ,FOS: Mathematics ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,asymptotic behavior ,MSC2020: 35Q89, 35K40, 35B40, 35A01, 35D30 ,Analysis ,Analysis of PDEs (math.AP) - Abstract
The paper considers a forward-backward system of parabolic PDEs arising in a Mean Field Game (MFG) model where every agent controls the drift of a trajectory subject to Brownian diffusion, trying to escape a given bounded domain $\Omega$ in minimal expected time. The important point is that agents are constrained by a bound on the drift depending on the density of the other agents at their location (the higher the density, the smaller the velocity). Existence for a finite time horizon $T$ is proven via a fixed point argument but, because of the diffusion, the model should be studied in infinite horizon as the total mass inside the domain decreases in time, but never reaches zero in finite time. Hence, estimates are needed to pass the solution to the limit as $T\to\infty$, and the asymptotic behavior of the solution which is obtained in this way is also studied. This passes through a combination of classical parabolic arguments together with specific computations for MFGs. Both the Fokker--Planck equation ruling the evolution of the density of agents and the Hamilton--Jacobi--Bellman equation on the value function display Dirichlet boundary conditions as a consequence of the fact that agents stop as soon as they reach $\partial\Omega$. The initial datum for the density is given (and its regularity is discussed so as to have the sharpest result), and the long-time limit of the value function is characterized as the solution of a stationary problem.
- Published
- 2020
6. Influence of a road on a population in an ecological niche facing climate change
- Author
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Henri Berestycki, Luca Rossi, Romain Ducasse, Centre d'Analyse et de Mathématique sociales (CAMS), École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS), Institut de Mathématiques de Marseille (I2M), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Dipartimento di Matematica [padova], Universita degli Studi di Padova, Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Università degli Studi di Padova = University of Padua (Unipd)
- Subjects
35B53 ,Computer science ,Population Dynamics ,Population ,Niche ,Climate change ,generalized principal eigenvalue ,reaction-diffusion system ,92D25 ,01 natural sciences ,010305 fluids & plasmas ,forced speed ,03 medical and health sciences ,Mathematics - Analysis of PDEs ,ecological niche ,KPP equations ,line with fast diffusion ,moving environment ,0103 physical sciences ,FOS: Mathematics ,Econometrics ,Quantitative Biology::Populations and Evolution ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,Set (psychology) ,education ,gen- eralized principal eigenvalue ,Ecosystem ,030304 developmental biology ,Ecological niche ,0303 health sciences ,education.field_of_study ,Extinction ,Plane (geometry) ,Applied Mathematics ,35B40 ,eco- logical niche MSC: 35K57 ,35K40 ,Agricultural and Biological Sciences (miscellaneous) ,climate change ,Modeling and Simulation ,Line (geometry) ,Analysis of PDEs (math.AP) - Abstract
We introduce a model designed to account for the influence of a line with fast diffusion-such as a road or another transport network-on the dynamics of a population in an ecological niche. This model consists of a system of coupled reaction-diffusion equations set on domains with different dimensions (line / plane). We first show that the presence of the line is always deleterious and can even lead the population to extinction. Next, we consider the case where the niche is subject to a displacement, representing the effect of a climate change or of seasonal variation of resources. We find that in such case the presence of the line with fast diffusion can help the population to persist. We also study several qualitative properties of this system. The analysis is based on a notion of generalized principal eigenvalue developed by the authors in [5].
- Published
- 2019
7. Threshold phenomenon and traveling waves for heterogeneous integral equations and epidemic models
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Romain Ducasse, Laboratoire Jacques-Louis Lions (LJLL (UMR_7598)), Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Mathématiques de Marseille (I2M), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
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threshold phenomenon ,Applied Mathematics ,heterogeneous models ,integro-differential systems ,traveling waves ,Mathematics - Analysis of PDEs ,Epidemic Model ,FOS: Mathematics ,Nonlinear integral equations ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,anisotropic equations ,SIR model ,Analysis ,Analysis of PDEs (math.AP) - Abstract
We study some anisotropic heterogeneous nonlinear integral equations arising in epidemiology. We focus on the case where the heterogeneities are spatially periodic. In the first part of the paper, we show that the equations we consider exhibit a "threshold phenomenon". In the second part, we study the existence and non-existence of "traveling waves", and we provide a formula for the admissible speeds. In a third part, we apply our results to a spatial heterogeneous SIR model.
- Published
- 2019
8. Blocking and invasion for reaction–diffusion equations in periodic media
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Luca Rossi, Romain Ducasse, Centre d'Analyse et de Mathématique sociales (CAMS), and École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS)
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Bistability ,blocking phenomena ,Reaction-diffusion equations ,periodic equations ,stability ,travelling fronts ,01 natural sciences ,Domain (mathematical analysis) ,Mathematics - Analysis of PDEs ,propagation ,0103 physical sciences ,Reaction–diffusion system ,FOS: Mathematics ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,0101 mathematics ,Mathematics ,Block (data storage) ,domains with holes ,Blocking (linguistics) ,Applied Mathematics ,010102 general mathematics ,Mathematical analysis ,A domain ,invasion ,Homogeneous ,010307 mathematical physics ,spreading ,Focus (optics) ,Analysis ,Analysis of PDEs (math.AP) - Abstract
International audience; We investigate the large time behavior of solutions of reaction-diffusion equations with general reaction terms in periodic media. We first derive some conditions which guarantee that solutions with compactly supported initial data invade the domain. In particular, we relate such solutions with front-like solutions such as pulsating traveling fronts. Next, we focus on the homogeneous equation set in a domain with periodic holes, and specifically in the cases where fronts are not known to exist. We show how the geometry of the domain can block or allow invasion. We finally exhibit a periodic domain on which the propagation takes place in an asymmetric fashion, in the sense that the invasion occurs in a direction but is blocked in the opposite one.
- Published
- 2018
9. Propagation properties of reaction-diffusion equations in periodic domains
- Author
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Romain Ducasse, Centre d'Analyse et de Mathématique sociales (CAMS), and École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
35B51 ,elliptic equations ,01 natural sciences ,Domain (mathematical analysis) ,Mathematics - Analysis of PDEs ,Critical speed ,35K05 ,0103 physical sciences ,Reaction–diffusion system ,propagation ,domains with obstacles ,FOS: Mathematics ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,0101 mathematics ,MSC: 35A08, 35B30, 35K05, 35K57, 35B40 ,Heat kernel ,Mathematics ,domains with holes ,Numerical Analysis ,speed of propagation ,Applied Mathematics ,geometry of the domain ,010102 general mathematics ,Mathematical analysis ,35B40 ,parabolic equations ,35B06 ,periodic domains ,Parabolic partial differential equation ,Connection (mathematics) ,reaction-diffusion equations ,35K57 ,heat kernel ,010307 mathematical physics ,spreading ,Analysis ,Analysis of PDEs (math.AP) - Abstract
We study the phenomenon of invasion for heterogeneous reaction-diffusion equations in periodic domains with monostable and combustion reaction terms. We give an answer to a question raised by Berestycki, Hamel and Nadirashvili concerning the connection between the speed of invasion and the critical speed of fronts. To do so, we extend the classical Freidlin–Gartner formula to such equations and we derive some bounds on the speed of invasion using estimates on the heat kernel. We also give geometric conditions on the domain that ensure that the spreading occurs at the critical speed of fronts.
- Published
- 2017
- Full Text
- View/download PDF
10. Generalized principal eigenvalues for heterogeneous road–field systems
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Henri Berestycki, Luca Rossi, Romain Ducasse, Centre d'Analyse et de Mathématique sociales (CAMS), École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS), Institut de Mathématiques de Marseille (I2M), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), European Project: 321186,EC:FP7:ERC,ERC-2012-ADG_20120216,READI(2013), and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)
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road-field model ,General Mathematics ,Field (mathematics) ,generalized principal eigenvalue ,01 natural sciences ,Mathematics - Spectral Theory ,Mathematics - Analysis of PDEs ,FOS: Mathematics ,[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP] ,Applied mathematics ,Boundary value problem ,0101 mathematics ,Spectral Theory (math.SP) ,line with fast diffusion ,Systems of elliptic operators ,Eigenvalues and eigenvectors ,Mathematics ,Harnack's inequality ,Harnack inequality ,Plane (geometry) ,Applied Mathematics ,010102 general mathematics ,reaction-diffusion systems ,KPP equations ,Coupling (probability) ,010101 applied mathematics ,Line (geometry) ,Element (category theory) ,[MATH.MATH-SP]Mathematics [math]/Spectral Theory [math.SP] ,Analysis of PDEs (math.AP) - Abstract
This paper develops the notion and properties of the generalized principal eigenvalue for an elliptic system coupling an equation in a plane with one on a line in this plane, together with boundary conditions that express exchanges taking place between the plane and the line. This study is motivated by the reaction–diffusion model introduced by Berestycki, Roquejoffre and Rossi [The influence of a line with fast diffusion on Fisher–KPP propagation, J. Math. Biol. 66(4–5) (2013) 743–766] to describe the effect on biological invasions of networks with fast diffusion imbedded in a field. Here we study the eigenvalue associated with heterogeneous generalizations of this model. In a forthcoming work [Influence of a line with fast diffusion on an ecological niche, preprint (2018)] we show that persistence or extinction of the associated nonlinear evolution equation is fully accounted for by this generalized eigenvalue. A key element in the proofs is a new Harnack inequality that we establish for these systems and which is of independent interest.
- Published
- 2019
11. Effects of Translucency and Thickness of Lithium Disilicate-Reinforced Glass-Ceramic Veneers on the Degree of Conversion of a Purely Light-Curing Bonding Resin: An In Vitro Study
- Author
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Anthony Poca, Kenza De Peretti Della Rocca, Karim Nasr, Romain Ducassé, and Thibault Canceill
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light-curing composite resin ,dental ceramics ,glass-ceramics ,FTIR spectroscopy ,Organic chemistry ,QD241-441 - Abstract
The objective of this study was to evaluate the variations in the degree of conversion (DC) of a light-curing composite resin when the thickness or the translucency of lithium disilicate-enriched glass-ceramic veneers are modified. IPS e. max® CAD blocks of the MT-A2, LT-A2 and MO1 types were cut to obtain four slices with thicknesses ranging from 0.6 mm to 1 mm. A strictly light-curing composite resin (G-aenial Universal Injectable) was injected in the empty part of a silicone mold so that the veneer could then be inserted under digital pressure to the stop. A 40 s light cure (1400 mW/cm2) was then performed. Resin samples were analyzed using Fourier transform infrared (FTIR) spectroscopy. When the degree of translucency of the ceramic was modified, a decrease in the resin conversion rate was noted, but with a non-significant global p-value (p = 0.062). Interestingly, the degree of conversion of the light-curing composite resin was also modified when the ceramic’s thickness increased, especially when it was over 1 mm (DC0.6 > DC0.7 > DC0.8 > DC1; p < 0.0001). This confirms that the degree of conversion of a bonding material is very dependent on the ceramic’s thickness. Contradictory data are, however, found in the literature, where there are reports of an absence of a difference between the DC obtained with thicknesses of ceramics of 0.7 and 2 mm.
- Published
- 2023
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12. Thermodynamic properties of polyolefin solutions at high temperature: 2. Lower critical solubility temperatures for polybutene-1, polypentene-1 and poly(4-methylpentene-1) in hydrocarbon solvents and determination of the polymer-solvent interaction parameter for PB1 and one ethylene-propylene copolymer
- Author
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Gérard Charlet, Geneviève Delmas, and Romain Ducasse
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chemistry.chemical_classification ,Polymers and Plastics ,Organic Chemistry ,Polymer ,Flory–Huggins solution theory ,Lower critical solution temperature ,Polyolefin ,Solvent ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Physical chemistry ,Polybutene ,Solubility - Abstract
Lower critical solubility temperature (LCST) for 3 polyolefins, polybutene-1 (PB1), polypentene-1 (PP1) and poly(4-methylpentene-1) (P4MP1), and the x interaction parameter in concentrated solutions for PB1 and the 33% ethylene ethylene-propylene copolymer have been measured in linear, branched, cyclic alkanes and some other solvents. Effects on x of the equation of state term, of correlations of molecular orientations (CMO) and of the solvent steric hindrance were investigated. The solvent density ds is found to be a good empirical parameter to characterize the equation of state term and to correlate the LCST. The parameter d s d p (where dp is the polymer density) affords an excellent correlation for the LCST of all polyolefins in normal and branched alkanes (polyethylene (PE) excepted). In dilute solution (at the LCST) the effect of CMO and solvent steric hindrance could not be distinguished from equation of state effects. However, values of x, found to be higher in branched than in linear alkanes in solutions of the linear polymer (PE) but not with the branched PB1 and the copolymer, are indicative of the importance in concentrated solutions of CMO even at high temperatures (100°–135°C). Furthermore, the lowering of x from linear PE to the branched PE and to the ethylene-propylene copolymers, following the expected diminution of CMO in the corresponding melts, is another indication of the persistance of CMO at high temperature. Solvent steric hindrance is seen to lower x (measured here by gas-liquid chromatography).
- Published
- 1981
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