Concept

Équilibre corrélé

Publications associées (15)

Distributionally Robust Linear Quadratic Gaussian Regulator with Stationary Distributions

We study the Linear Quadratic Gaussian regulation problem in the face of worst-case noise distributions when these are mutually independent, zero-mean, stationary, and within a radius (as measured by the Wasserstein distance) of some reference Gaussian noise distributions. Compared with nonstationary ambiguity models, our stationary modeling choice reduces conservatism when the disturbances are stationary, as is often the case in practice. We first show optimality of linear output-feedback policies via the

Institute of Electrical and Electronics Engineers2026

Particle methods for optimization over the space of measures

Optimization problems over measures arise naturally in many areas of applied mathematics and machine learning, but solving them computationally requires dealing with the infinite-dimensional nature of the measure variables. This thesis focuses on particle methods, a class of algorithms that parametrize the variable by a finite sum of Dirac deltas and apply gradient-based updates to their positions. We analyze the convergence of these methods in several settings of practical relevance, leveraging ideas from

EPFL2026

Teaching Multivariational Reasoning Through AI-Guided Inquiry in Interactive Simulations

Understanding how students learn and enact multivariate quantitative inquiry strategies during science inquiry remains challenging, particularly in scalable instructional settings. Although strategies such as the extended Control of Variables Strategy (CVS++) and the General Principle Strategy (GPS) are known to support multivariate reasoning, less is known about how instruction can foster their uptake and sustained use during inquiry. We investigate this issue using a rule-based AI chatbot that scaffolds s

Springer2026

On Linear Quadratic Potential Games☆

Our paper addresses characterizing conditions for linear quadratic (LQ) games to be potential. The desired properties of potential games in finite action settings, such as convergence of learning dynamics to Nash equilibria and challenges of learning Nash equilibria in continuous state and action settings, motivate us to characterize LQ potential games. Our first contribution is to consider two-player LQ games with full-state feedback and scalar states and action space, and to analytically verify that the s

PERGAMON-ELSEVIER SCIENCE LTD2025

Feedforward equilibrium trajectory optimization with GSPulse

One of the common tasks required for designing new plasma scenarios or evaluating capabilities of a tokamak is to design the desired equilibria using a Grad-Shafranov (GS) equilibrium solver. However, most standard equilibrium solvers are time-independent and do not include dynamic effects such as plasma current flux consumption, induced vessel currents, or voltage constraints. Another class of tools, plasma equilibrium evolution simulators, do include time-dependent effects. These are generally structured

IOP Publishing Ltd2025

Overview of the RFX-mod fusion science activity

Wilfred Anthony Cooper, Federico Alberto Alfredo Felici, Yi Zhang, Nicola Vianello, Matteo Vallar

This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped reversed-field pinch equilibria ...

IOP Publishing Ltd2017

Tall and old Amazonian forests are more resilient to precipitation variability

Climate change is altering the natural equilibrium of the Amazon ecosystem, which is in turn deeply connected to the Earth’s biogeochemical cycles. Understanding this relationship aids optimal rainforests management in the future. Previous research has investigated the role of environmental variables and climatic drivers, neglecting the influence of forest height and age. This study uses remote sensing observations of precipitation, vapour-pressure deficit and canopy height along with model estimates of tre

2017

Numerical study of potential heat flux mitigation effects in the TCV snowflake divertor

Basil Duval, Holger Reimerdes, Benoît Labit, Marco Wischmeier, Wouter Vijvers

We report on EMC3-Eirene simulations of the plasma and neutral particle transport the TCV boundary layer of a series of snowflake (SF) equilibria characterized by the normalized poloidal flux coordinate rho(x2) of the secondary X-point x(2). We refer to a ...

2016

Stabilization of the vertical instability by non-axisymmetric coils

Wilfred Anthony Cooper

In a published Physical Review Letter (Reiman 2007 Phys. Rev. Lett. 99 135007), it was shown that axisymmetric (or vertical) stability can be improved by placing a set of parallelogram coils above and below the plasma oriented at an angle to the constant t ...

IOP Publishing Ltd2016

Effects of magnetic ripple on 3D equilibrium and alpha particle confinement in the European DEMO

Ambrogio Fasoli, Jonathan Graves, Wilfred Anthony Cooper, David Pfefferlé

An assessment of alpha particle confinement is performed in the European DEMO reference design. 3D MHD equilibria with nested flux-surfaces and single magnetic axis are obtained with the VMEC free-boundary code, thereby including the plasma response to the ...

IOP Science2016

VENUS-LEVIS and its spline-Fourier interpolation of 3D toroidal magnetic field representation for guiding-centre and full-orbit simulations of charged energetic particles

Jonathan Graves, Wilfred Anthony Cooper, David Pfefferlé

Curvilinear guiding-centre drift and full-orbit equations of motion are presented as implemented in the code{VENUS-LEVIS} code. A dedicated interpolation scheme based on Fourier reconstruction in the toroidal and poloidal direction and cubic spline in the ...

Elsevier2014

Collaborative Housing and the Intermediation of Moral Hazard

This paper considers intermediation in a di_erentiated short-term housing market where heterogeneous agents may stay at a hotel or at one of several private hosts' properties, below or above hotel quality. The collaborative-housing market fails when agents' hidden actions are noncontractable. If expected liability is not excessive, a trusted intermediary can induce agents to exert first-best effort and fully insure the hosts' risks, without subsidizing the transactions. The intermediary can also extract the

EPFL CDM MTEI2013

Ideal MHD stability of helically symmetric magnetic islands

A new version of the MHD_NX code, that computes the ideal MHD stability of helically symmetric equilibria with arbitrary topology of magnetic surfaces, was applied to the investigation of equilibrium magnetic islands in tokamak-like conditions. Any helical deformation of the plasma boundary shape from a circular cylinder results in the breaking of topology of the helical ﬂux level lines and appearance of magnetic islands at the place of the magnetic surface q = m/n in the original large aspect ratio

European Physical Society2012

Welfare-Maximizing Correlated Equilibria with an Application to Wireless Communication

The set of correlated equilibria is convex and contains all Nash equilibria as special cases. Thus, the social welfare-maximizing correlated equilibrium is amenable to convex analysis and offers social welfare that is at least as good as the game s best performing Nash equilibria.We employ robust semidefinite programming (SDP) for computing the social welfare-maximizing correlated equilibria in static polynomial games, giving rise to a dedicated sequential SDP algorithm, the first of this type that can cope

2011

Experimental study of the out-of-equilibrium behavior of the two-way shape memory effect

Yves Bellouard, Reymond Clavel

The Two-Way Shape Memory Effect (TWSME) has been widely studied in the literature. However, little attention has been paid about the out-of-equilibrium behavior of the TWSME. This paper reports some experiments, which were performed on specimens, previously trained in bending according a constrained temperature cycling process. Once the training process was done, specimens were deformed in their martensitic state such as a permanent deformation remains. In other words, specimens were set in a position that

2003

Graph Chat

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

Publications associées (15)

VENUS-LEVIS and its spline-Fourier interpolation of 3D toroidal magnetic field representation for guiding-centre and full-orbit simulations of charged energetic particles

Jonathan Graves, Wilfred Anthony Cooper, David Pfefferlé

Elsevier2014