Publications associées à Racine carrée d'une matrice

Principal Component Analysis By Optimization Of Symmetric Functions Has No Spurious Local Optima

Principal component analysis (PCA) finds the best linear representation of data and is an indispensable tool in many learning and inference tasks. Classically, principal components of a dataset are interpreted as the directions that preserve most of its "e ...

SIAM PUBLICATIONS2020

Decompositions of dependence for high-dimensional extremes

Emeric Rolland Georges Thibaud

We propose two decompositions that help to summarize and describe high-dimensional tail dependence within the framework of regular variation. We use a transformation to define a vector space on the positive orthant and show that transformed-linear operatio ...

OXFORD UNIV PRESS2019

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments

Olivier Sauter, Basil Duval, Stefano Coda, Timothy Goodman, Yves Martin, Jean-Marc Moret, Duccio Testa, Patrick Blanchard, Holger Reimerdes, Benoît Labit, Christian Gabriel Theiler, Alessandro Pau, Federico Alberto Alfredo Felici, Cristian Sommariva, Laurie Porte, Alexander Karpushov, Marc Gruber, Antoine Pierre Emmanuel Alexis Merle, Joan Decker, Umar Sheikh, Cristian Galperti, Yanis Andrebe, Haomin Sun, Richard Pitts, Yann Camenen, Jan Horacek, Roland Behn, Javier García Hernández, Marco Wischmeier, Nicola Vianello, Federico Nespoli, Antonio José Pereira de Figueiredo, Alberto Bottino, Emiliano Fable, Ben McMillan, Andrea Scarabosio, Cedric Kar-Wai Tsui, Doohyun Kim, Kevin Henricus Annemarie Verhaegh, Wouter Vijvers, Anna Teplukhina, Zhouji Huang, Dávid Wágner, Claudio Marini, Thomas Binderup Jensen, Hoang Bao Le, Himank Anand, Attila Bencze, Heinz Mueller, Donghyun Kim, Xiao Wang, Bernhard Sieglin, Otto Asunta, Hartmut Zohm, Emanuele Poli, Gergely Papp, Giovanni Tardini

In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap ante ...

2019

MATHICSE Technical Report : On maximum volume submatrices and cross approximation for symmetric semidefinite and diagonally dominant matrices

Daniel Kressner, Stefano Massei, Alice Cortinovis

The problem of finding a

k\times k

submatrix of maximum volume of a matrix A is of interest in a variety of applications. For example, it yields a quasi-best low-rank approximation constructed from the rows and columns of A. We show that such a submatrix ...

MATHICSE2019

H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

Olivier Sauter, Alessandro Marinoni

Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for ...

2019

Rational Krylov for Stieltjes matrix functions: convergence and pole selection

Stefano Massei

Evaluating the action of a matrix function on a vector, that is

x=f(\mathcal M)v

, is an ubiquitous task in applications. When

\mathcal M

is large, one usually relies on Krylov projection methods. In this paper, we provide effective choices for the pole ...

2019

Global eigenvalue distribution of matrices defined by the skew-shift

Marius Christopher Lemm

We consider large Hermitian matrices whose entries are defined by evaluating the exponential function along orbits of the skew-shift

\binom{j}{2} \omega+jy+x \mod 1

for irrational

\omega

. We prove that the eigenvalue distribution of these matrices conv ...

2019

Almost surely constrained convex optimization

Volkan Cevher, Ahmet Alacaoglu

We propose a stochastic gradient framework for solving stochastic composite convex optimization problems with (possibly) infinite number of linear inclusion constraints that need to be satisfied almost surely. We use smoothing and homotopy techniques to ha ...

2019

Turbulent transport in TCV plasmas with positive and negative triangularity

Stefano Coda, Laurie Porte, Gabriele Merlo, Matteo Fontana

Local gyrokinetic simulations with the GENE code are used to investigate the turbulent transport for different levels of neutral beam injection heating power in the Tokamak a Configuration Variable (TCV) for plasmas with both positive and negative edge tri ...

2019

The effect of triangularity on fluctuations in a tokamak plasma

Olivier Sauter, Stefano Coda, Laurie Porte

The effects of plasma shaping, in particular triangularity (d), on temperature fluctuations in the tokamak a configuration variable have been studied using the correlation electron cyclotron emission system. It has been found that, in ohmic discharges with ...

2018

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Principal Component Analysis By Optimization Of Symmetric Functions Has No Spurious Local Optima

Decompositions of dependence for high-dimensional extremes

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments

MATHICSE Technical Report : On maximum volume submatrices and cross approximation for symmetric semidefinite and diagonally dominant matrices

H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

Rational Krylov for Stieltjes matrix functions: convergence and pole selection

Global eigenvalue distribution of matrices defined by the skew-shift

Almost surely constrained convex optimization

Turbulent transport in TCV plasmas with positive and negative triangularity

The effect of triangularity on fluctuations in a tokamak plasma

Principal Component Analysis By Optimization Of Symmetric Functions Has No Spurious Local Optima

MATHICSE Technical Report : On maximum volume submatrices and cross approximation for symmetric semidefinite and diagonally dominant matrices

Global eigenvalue distribution of matrices defined by the skew-shift

Rational Krylov for Stieltjes matrix functions: convergence and pole selection

Turbulent transport in TCV plasmas with positive and negative triangularity

Decompositions of dependence for high-dimensional extremes

H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

Almost surely constrained convex optimization

The effect of triangularity on fluctuations in a tokamak plasma

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments