Publications associées à 2-forme de courbure

An Accelerated First-Order Method for Non-convex Optimization on Manifolds

Nicolas Boumal, Christopher Arnold Criscitiello

We describe the first gradient methods on Riemannian manifolds to achieve accelerated rates in the non-convex case. Under Lipschitz assumptions on the Riemannian gradient and Hessian of the cost function, these methods find approximate first-order critical ...

SPRINGER2022

Full field dependence of primary aberrations in perturbed double-plane symmetric systems with a circular pupil

Toralf Scharf, Alessandro Grosso

This paper deals with the theory of primary aberrations for perturbed double-plane symmetric optical systems consisting of a combination of tilted and decentered surfaces and a circular pupil. First, the analytical expressions describing the full field beh ...

OPTICAL SOC AMER2020

Robustness via curvature regularization, and vice versa

Pascal Frossard, Seyed Mohsen Moosavi Dezfooli, Alhussein Fawzi

State-of-the-art classifiers have been shown to be largely vulnerable to adversarial perturbations. One of the most effective strategies to improve robustness is adversarial training. In this paper, we investigate the effect of adversarial training on the ...

IEEE2019

Robust Maximization of Non-Submodular Objectives

Volkan Cevher, Ilija Bogunovic, Junyao Zhao

We study the problem of maximizing a monotone set function subject to a cardinality constraint k in the setting where some number of elements is deleted from the returned set. The focus of this work is on the worst-case adversarial setting. While there exi ...

2018

Hybrid guiding-centre/full-orbit simulations in non-axisymmetric magnetic geometry exploiting general criterion for guiding-centre accuracy

Jonathan Graves, Wilfred Anthony Cooper, David Pfefferlé

To identify under what conditions guiding-centre or full-orbit tracing should be used, an estimation of the spatial variation of the magnetic field is proposed, not only taking into account gradient and curvature terms but also parallel currents and the lo ...

Iop Publishing Ltd2015

Energetic ion dynamics and confinement in 3D saturated MHD configurations

David Pfefferlé

In the following theoretical and numerically oriented work, a number of findings have been assembled. The newly devised VENUS-LEVIS code, designed to accurately solve the motion of energetic particles in the presence of 3D magnetic fields, relies on a non- ...

EPFL2015

Note on Solutions of the Strominger System from Unitary Representations of Cocompact Lattices of SL(2, C)

Mario Garcia Fernandez

This note is motivated by a recently published paper (Biswas and Mukherjee in Commun Math Phys 322(2):373-384, 2013). We prove a no-go result for the existence of suitable solutions of the Strominger system in a compact complex parallelizable manifold . Fo ...

Springer Verlag2014

Principal Flows

Victor Panaretos, Tung Huy Pham, Zhigang Yao

We revisit the problem of extending the notion of principal component analysis (PCA) to multivariate datasets that satisfy nonlinear constraints, therefore lying on Riemannian manifolds. Our aim is to determine curves on the manifold that retain their cano ...

American Statistical Association2014

Planck 2013 results. XXVI. Background geometry and topology of the Universe

Julien Lesgourgues, Jason Douglas McEwen, Fabio Finelli

The new cosmic microwave background (CMB) temperature maps from Planck provide the highest-quality full-sky view of the surface of last scattering available to date. This allows us to detect possible departures from the standard model of a globally homogen ...

Edp Sciences S A2014

Finite Dimensional Methods for Differential Flatness

Basile Graf

In Control System Theory, the study of continuous-time, finite dimensional, underdetermined systems of ordinary differential equations is an important topic. Classification of systems in different categories is a natural initial step to the analysis of a g ...

EPFL2013

Phase-field modeling of micropore formation in a solidifying alloy

Hossein Meidani

This thesis is focused on the study of the morphology of micropores formed during solidification of metallic alloys. Micropores constrained to form in well-developed dendritic solid network adopt complex non-spherical shapes. Previous studies using X-ray t ...

EPFL2013

The quantum mechanics of perfect fluids

Riccardo Rattazzi, Solomon G Shamsuddin Osman Endlich

We consider the canonical quantization of an ordinary fluid. The resulting long-distance effective field theory is derivatively coupled, and therefore strongly coupled in the UV. The system however exhibits a number of peculiarities, associated with the vo ...

Springer Nature2011

Déformations conformes des variétés de Finsler-Ehresmann

Ratiba Djelid

An intrinsic approach to Finsler geometry is proposed. A concept of Finsler- Ehresmann manifold, denoted by (M,F,H), is introduced and a generalized Chern connection is built for this manifold. Conformal deformations on this manifold are considered. First, ...

EPFL2011

State-specific studies of internal mixing in a prototypical flexible bichromophore: Diphenylmethane

Laser-induced fluorescence, resonant two-photon ionization, UV-UV hole burning, UV depletion, and single vibronic level fluorescence (SVLF) spectra of jet-cooled diphenylmethane (DPM) have been recorded over the 37 300 - 38 400 cm(-1) region that encompass ...

2008