Concept

Géométrie conforme

Publications associées (134)

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Stability of Equilibria for the so(4) Free Rigid Body

Tudor Ratiu, Murat Turhan

The stability for all generic equilibria of the Lie-Poisson dynamics of the so(4) rigid body dynamics is completely determined. It is shown that for the generalized rigid body certain Cartan subalgebras (called of coordinate type) of so(n) are equilibrium ...

2012

Learning pattern transformation manifolds with parametric atom selection

Pascal Frossard, Elif Vural

We address the problem of building a manifold in order to represent a set of geometrically transformed images by selecting a good common sparse approximation of them with parametric atoms. We propose a greedy method to construct a representative pattern su ...

2011

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

Approximation of Pattern Transformation Manifolds with Parametric Dictionaries

Pascal Frossard, Elif Vural

The construction of low-dimensional models explaining high-dimensional signal observations provides concise and efficient data representations. In this paper, we focus on pattern transformation manifold models generated by in-plane geometric transformation ...

2011

Central charge bounds in 4D conformal field theory

Riccardo Rattazzi, Alessandro Vichi

We derive model-independent lower bounds on the stress tensor central charge C-T in terms of the operator content of a 4-dimensional conformal field theory. More precisely, C-T is bounded from below by a universal function of the dimensions of the lowest a ...

2011

Bounds in 4D conformal field theories with global symmetry

Riccardo Rattazzi, Alessandro Vichi

We explore the constraining power of OPE associativity in 4D conformal field theory with a continuous global symmetry group. We give a general analysis of crossing symmetry constraints in the 4-point function , where phi is ...

2011

Spinning conformal correlators

We develop the embedding formalism for conformal field theories, aimed at doing computations with symmetric traceless operators of arbitrary spin. We use an index-free notation where tensors are encoded by polynomials in auxiliary polarization vectors. The ...

Springer2011

Spinning conformal blocks

For conformal field theories in arbitrary dimensions, we introduce a method to derive the conformal blocks corresponding to the exchange of a traceless symmetric tensor appearing in four point functions of operators with spin. Using the embedding space for ...

Springer2011

Nonlinear Optical Response in Single Alkaline Niobate Nanowires

Aleksandra Radenovic, Kurt Schenk, Fabrizia Dutto, Camille Alice Raillon

We have synthesized and characterized three types of perovskite alkaline niobate nanowires: NaNbO3, KNbO3, and LiNbO3 (XNbO3). All three types of nanowires exhibit strong nonlinear response. Confocal imaging has been employed to quantitatively compare the ...

2011

Nonlinear quasisteady state benchmark of global gyrokinetic codes

Laurent Villard, Stephan Brunner, Ben McMillan, Xavier Lapillonne

Two global gyrokinetic codes are benchmarked against each other by comparing simulation results in the case of ion temperature gradient driven turbulence, in the adiabatic electron response limit The two codes are the Eulerian code GENE and the Lagrangian ...

American Institute of Physics2010