Concept

Mesure de Dirac

Publications associées (18)

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

Photonic exceptional points in engineered materials and their emerging applications

Enabled by the coalescence of eigenvalues and eigenstates, exceptional points (EPs) in non-Hermitian photonic systems have revolutionized the control of light–matter interactions and sparked growing interest across diverse material and structural platforms. This Review synthesizes advances in engineered materials that harness EPs across three key domains: band EPs in dielectric photonic crystals, wherein radiation-induced loss transforms Hermitian degeneracies into exceptional rings and bulk Fermi arcs; sca

Springer Science and Business Media LLC2026

Non-Hermitian trapping of Dirac exciton-polariton condensates in a perovskite metasurface

Massless Dirac particles avoid trapping because of their exceptional tunneling properties manifested in the so-called Klein paradox. This conclusion stems from the conservative treatment, but so far, it has not been extended to a non-Hermitian framework. Recently, driven-dissipative bosonic condensation of exciton-polaritons featuring Dirac dispersion was demonstrated in metasurface waveguides—a platform rich in non-Hermitian effects. Here, we report an experimental observation of spatial binding and energy

American Association for the Advancement of Science (AAAS)2026

Electronic states at twist stacking faults in rhombohedral graphite

Flat bands in graphitic materials emerged as a platform for realizing tunable correlated physics. As a nodal-line semimetal, rhombohedral graphite features flat drumhead surface states in the vicinity of the Dirac points, which carry a nontrivial topological charge. We present a comprehensive study on rhombohedral graphite with twist stacking faults. Using both the continuum models and the realistic tight-binding models, we show that the twist angle between the graphene layers can tune the interface states

American Physical Society (APS)2026

Study of the fast-ion confinement via velocity-space resolved measurements in several plasma scenarios in the TCV tokamak

The Fast Ion Loss Detector (FILD), installed on TCV in 2020 was redesigned and upgraded several times throughout this PhD. The collimator apertures were reduced to increase the energy resolution, a faster CMOS camera was intalled, a novel fast camera (up to 4 MHz) was installed to access microsecond velocity-space mapping, two more slits were added on the bottom partof the FILD head accessing to all magnetic field configurations, a bandpass optical filter was installed to reduce residual light contamination

EPFL2026

Spin-orbit Control of Dirac Points and Topological End States in Inverted Gap Nanowires Under a Transverse Electric Field

We predict that broken-gap InAs/GaSb core/shell nanowires, when operating in the topological insulating regime, undergo a collapse of the hybridization gap under the application of a transverse electric field. We perform predictive, self-consistent k p calculations for realistic nanostructures and show that a gap closure occurs at two Kramers-related, massless Dirac points at a critical value of the field in the V/,a range. An analysis based on the Bernevig-Hughes-Zhang model shows that the new

AMER PHYSICAL SOC2025

On the Implementation of a Qualification Model for Nuclear Safety Codes, and its Application to the Verification & Validation of OFFBEAT

Based on regulatory guidelines and established systems engineering principles, this work proposes the adoption of the V-Model as a structured quality assurance framework for nuclear safety assessment computer codes. This universally applicable framework, which makes the relation between individual development and testing phases of a code explicit, is subsequently applied to the open-source fuel performance code OFFBEAT. This exercise shows the clear hierarchical - and thereby scalable - structure of the pro

American Nuclear Society2025

Nonlocal Traffic Models with General Kernels: Singular Limit, Entropy Admissibility, and Convergence Rate

Nonlocal conservation laws (the signature feature being that the flux function depends on the solution through the convolution with a given kernel) are extensively used in the modeling of vehicular traffic. In this work we discuss the singular local limit, namely the convergence of the nonlocal solutions to the entropy admissible solution of the conservation law obtained by replacing the convolution kernel with a Dirac delta. While recent counter-examples rule out convergence in the general case, in the spe

Springer2023

Local limit of nonlocal traffic models: Convergence results and total variation blow-up

Consider a nonlocal conservation law where the flux function depends on the convolution of the solution with a given kernel. In the singular local limit obtained by letting the convolution kernel converge to the Dirac delta one formally recovers a conservation law. However, recent counter-examples show that in general the solutions of the nonlocal equations do not converge to a solution of the conservation law. In this work we focus on nonlocal conservation laws modeling vehicular traffic: in this case, the

EMS Press2021

An anomalous metal-rich phosphogypsum: Characterization and classification according to international regulations

Phosphogypsum is the main waste generated by the phosphate fertilizer industry. Despite the high level of pollutants found in phosphogypsum and the proximity of stacks to cities, there are no specific regulations for the management of this waste. This stud ...

Elsevier Science Bv2017

Sparse Gammatone Signal Model Predicts Perceived Noise Intrusiveness

Is it possible to predict the intrusiveness of background noise in speech signals as perceived by humans? Such a question is important to the automatic evaluation of speech enhancement systems, including those designed for new wideband speech telephony, and the goal of a future ITU quality assessment standard. In this paper, we show that this is possible by modeling the encoding of the noise signal at the auditory nerve. Indeed, recent research suggests that sparse signal representations may be indicative o

Idiap2014

Comparing connectomes across subjects and populations at different scales

Jean-Philippe Thiran, Stephan Morgenthaler, Alessandra Griffa, Elda Fischi Gomez, Patric Hagmann, Djalel Eddine Meskaldji

Brain connectivity can be represented by a network that enables the comparison of the different patterns of struc- tural and functional connectivity among individuals. In the literature, two levels ofstatistical analysis have been con- sidered in comparing ...

2013

Anomalously enhanced photoemission from the Dirac point and other peculiarities in the self-energy of the surface-state quasiparticles in Bi2Se3

Helmuth Berger

Line-shape analysis of the photoemission intensity from the surface states of Bi2Se3 reveals two unusual features: spectral line asymmetry and anomalously enhanced photoemission from the Dirac point. The former can be described by the one-particle spectral ...

2012

Determination of minimum conductivity of graphene from contactless microwaves measurements

Julien Perruisseau-Carrier

We report a non-direct method to determine the minimum conductivity (sigma(min)) of graphene. The proposed technique is based on the prior characterization of graphene sheet impedance at microwave frequencies using waveguides, and on the subsequent extraction of sigma(min) from the measured scattering rate. This approach presents some advantages as compared with standard DC characterization methods, as it is inherently contactless and does not require graphene patterning. Our experimental study estimates a

Ieee2012

A Design of Experiments based Method for the Characterisation of Solid Oxide Fuel Cells

Jan Van Herle

We apply a Design of Experiments methodology for Non-linear models on a simplified model for Solid Oxide Fuel Cells in order to define optimal measurement points. The behaviour of D-optimality criterion is studied as regards the number of measuring points and the number of total measurements.

2010

Analytical Footprints: Compact Representation of Elementary Singularities in Wavelet Bases

Michaël Unser, Dimitri Nestor Alice Van De Ville, Thierry Blu

We introduce a family of elementary singularities that are point-Holder alpha-regular. These singularities are self-similar and are the Green functions of fractional derivative operators; i.e., by suitable fractional differentiation, one retrieves a Dirac ...

Institute of Electrical and Electronics Engineers2010

Convolution Operators And Homomorphisms Of Locally Compact Groups

Let 1 < p < infinity, let G and H be locally compact groups and let c) be a continuous homomorphism of G into H. We prove, if G is amenable, the existence of a linear contraction of the Banach algebra CVp (G) of the p-convolution operators on G into CVp (H ...

Cambridge University Press2008

The Complexity of Asynchronous Byzantine Consensus

Rachid Guerraoui, Partha Dutta

This paper establishes the first theorem relating resilience, round complexity and authentication in distributed computing. We give an exact measure of the time complexity of consensus algorithms that tolerate Byzantine failures and arbitrary long periods of asynchrony as in the Internet. The measure expresses the ability of processes to reach a consensus decision in a minimal number of rounds of information exchange, as a function of (a) the ability to use authentication and (b) the number of actual proces

2004

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Publications associées (18)

Study of the fast-ion confinement via velocity-space resolved measurements in several plasma scenarios in the TCV tokamak

EPFL2026

Spin-orbit Control of Dirac Points and Topological End States in Inverted Gap Nanowires Under a Transverse Electric Field

AMER PHYSICAL SOC2025

On the Implementation of a Qualification Model for Nuclear Safety Codes, and its Application to the Verification & Validation of OFFBEAT

American Nuclear Society2025

Anomalously enhanced photoemission from the Dirac point and other peculiarities in the self-energy of the surface-state quasiparticles in Bi2Se3

Helmuth Berger

2012