Publications related to Lie derivative

On the commutativity of flows of rough vector fields

In the class of Sobolev vector fields in R-n of bounded divergence, for which the theory of DiPerna and Lions provides a well defined notion of flow, we characterize the vector fields whose flow commutes in terms of the Lie bracket and of a regularity cond ...

ELSEVIER2022

Covariant formulation of relativistic mechanics

Miguel Alexandre Ribeiro Correia

Accretion disks surrounding compact objects, and other environmental factors, deviate satellites from geodetic motion. Unfortunately, setting up the equations of motion for such relativistic trajectories is not as simple as in Newtonian mechanics. The prin ...

American Physical Society2022

Characterization of the traces on the boundary of functions in magnetic Sobolev spaces

Hoài-Minh Nguyên

We characterize the trace of magnetic Sobolev spaces defined in a half-space or in a smooth bounded domain in which the magnetic field Ais differentiable and its exterior derivative corresponding to the magnetic field dAis bounded. In particular, we prove ...

2020

Joint Angular Refinement and Reconstruction for Single-Particle Cryo-EM

Michaël Unser, Laurène Donati, Emmanuel Emilien Louis Soubies, Mona Zehni

Single-particle cryo-electron microscopy (cryo-EM) reconstructs the three-dimensional (3D) structure of bio-molecules from a large set of 2D projection images with random and unknown orientations. A crucial step in the single-particle cryo-EM pipeline is 3 ...

2020

$A_1$-type subgroups containing regular unipotent elements

Donna Testerman

Let be a simple exceptional algebraic group of adjoint type over an algebraically closed field of characteristic and let be a subgroup of containing a regular unipotent element of . By a theorem of Testerman, is contained in a connected subgroup of of type ...

2019

Sur quelques équations aux dérivées partielles en lien avec le lemme de Poincaré

David Valentin Strütt

In this thesis, we study two distinct problems. The first problem consists of studying the linear system of partial differential equations which consists of taking a k-form, and applying the exterior derivative 'd' to it and add the wedge product with a 1- ...

EPFL2018

Nonlinear PD control of a Parallel Delta robot: Expermentals Results

Mohamed Bouri

In this paper, a nonlinear proportional derivative control (NPD) is proposed to solve the trajectory tracking problem of a parallel Delta robot. In order to handle the strong coupling effect and external disturbances as well as to realise high-precision tr ...

IEEE2018

Some Remarks on the Lie Derivative and the Pullback Equation for Contact Forms

Bernard Dacorogna, Olivier Kneuss

Given the contact forms f and g, and the 1-form h, we discuss the existence of a vector field u verifying L-u(f)= d(u (right perpendicular) f)+ u (right perpendicular) df = h. This is closely related to the pullback equation, where we seek for a diffeomorp ...

Walter De Gruyter Gmbh2017

On the geometrical interpretation of scale-invariant models of inflation

Georgios Karananas, Javier Rubio

We study the geometrical properties of scale-invariant two-field models of inflation. In particular, we show that when the field-derivative space in the Einstein frame is maximally symmetric during inflation, the inflationary predictions can be universal a ...

Elsevier2016

Discrete variational Lie group formulation of geometrically exact beams dynamics

Yves Weinand, Tudor Ratiu, François Gay-Balmaz, François Marie Alain Demoures

The goal of this paper is to derive a structure preserving integrator for geometrically exact beam dynamics, by using a Lie group variational integrator. Both spatial and temporal discretization are implemented in a geometry preserving manner. The resultin ...

Springer2015

Local nonreflecting boundary condition for time-dependent multiple scattering

Imbo Sim

Starting from from a high-order local nonreflecting boundary condition (NBC) for single scattering [25], we derive a local NBC for time-dependent multiple scattering problems in three space dimensions, which is completely local both in space and time. To d ...

2011

The Choice of Polar Stationary Phases for Gas-Liquid Chromatography by Statistical Analysis of Retention Data

Stephan Morgenthaler

We have studied the retention indices of 127 volatile substances on a C-78-paraffin and on its seven nearly isochor and isomorphous polar derivatives over a temperature range of 90-210 A degrees C. The retention index of a substance on the C-78 paraffin ha ...

Springer Verlag2009

White matter fiber tract segmentation in DT-MRI using geometric flows

Jean-Philippe Thiran, Patric Hagmann, Reto Meuli, Xavier Bresson, Olivier Cuisenaire, Lisa Jonasson

In this paper, we present a 3D geometric flow designed to segment the main core of fiber tracts in diffusion tensor magnetic resonance images. The fundamental assumption of our fiber segmentation technique is that adjacent voxels in a tract have similar pr ...

2005