arXiv subjects

Géry de Saxcé

Publications and source records attributed to Géry de Saxcé.

12 recordsLinked to original sources

arXiv2026

On Jean-Marie Souriau's geometric quantization of the relativistic electron

The aim of this paper is to revisit, in Souriau's book "Structure of Dynamical Systems", the chapter devoted to the geometric quantization where the justifications of important results and formulae are not given and are difficult to prove. After recalling the coadjoint orbit method and its application to the relativistic particle with spin, we state and prove two keystone theorems that allow to equip its prequantum manifold with the symplectic and contact structures. We apply them to the relativistic particle with spin 1/2, leading to the Dirac equation and the conservation of the probability current. We propose also an identity of conservation of the spin current and, invoking the Kaluza-Klein theory, a systematic construction of the symmetries of charge conjugation, parity transformation and time reversal which seems to us more convenient and readable than that of the classical presentations.

math-ph↗

arXiv2026

Variational theory of Cosserat arches and affine tensors

Our purpose is to revisit the screw theory in light of the affine tensor formalism, introducing the co-momentum and momentum tensors. Our target-applications of the Euler-Poincaré equation are problems of mechanics such as the motion of the rigid body or the statics and the dynamics of Cosserat arches, in relation to the concept of momentum tensor. Using the framework of Ehresmann connections on the principal bundle of affine frames, we show that the Euler-Poincaré equation means that the momentum tensor is parallel-transported.

math-ph↗

arXiv2026

A family of variational principles of minima for the plasticity, the friction contact and the fracture mechanics

The paper is a synthesis of several works on the variational principles for application to the mechanics and the physics, inspired from original ideas of Brezis, Ekeland and Nayroles. On this basis, we developed an unified framework for dynamic dissipative systems that leads to a space-time variational principle of minimum constructed with tools of convex analysis and symplectic geometry. We stress the essential ideas and concepts. They are illustrated with various theoretical and numerical examples.

math-ph↗

arXiv2025

Electric? Then it is geometric

In this work, we revisit Kaluza-Klein theory from the perspective of the classification of elementary particles based on the coadjoint orbit method. We propose a symmetry group for which the electric charge is invariant and, on this basis, a cosmological scenario in which the three former spatial dimensions inflate quickly while the fifth one shrinks, leading to a 4D era where the particles correspond to the coadjoint orbits of this group. By this mechanism, the elementary particles can acquire electric charge as a by-product of the 4 + 1 symmetry breaking of the Universe. By pullback over the space-time, we construct the non-Riemannian connection corresponding to this symmetry group, allowing to recover conservation of the charge and the equation of motion with the Lorentz force. On this ground, we develop a five dimensional extension of the variational relativity allowing to deduce in the classical limit Maxwell's equation.

physics.gen-ph↗

arXiv2024

Cosserat media in dynamics

Our aim is to develop a general approach for the dynamics of material bodies of dimension d represented by a mater manifold of dimension (d + 1) embedded into the space-time. It can be declined for d = 0 (pointwise object), d = 1 (arch if it is a solid, flow in a pipe or jet if it is a fluid), d = 2 (plate or shell if it is a solid, sheet of fluid), d = 3 (bulky bodies). We call torsor a skew-symmetric bilinear map on the vector space of affine real functions on the affine tangent space to the space-time. We use the affine connections as originally developed by Élie Cartan, that is the connections associated to the affine group. We introduce a general principle of covariant divergence free torsor from which we deduce 10 balance equations. We show the relevance of this general principle by applying it for d from 1 to 4 in the context of the Galilean relativity.

math.GM↗

arXiv2024

Symplectic bipotentials

In a previous paper, we proposed a symplectic version of Brezis-Ekeland-Nayroles principle based on the concepts of Hamiltonian inclusions and symplectic polar functions. We applied it to the standard plasticity. The object of this work is to extend the previous formalism to non associated plasticity. For this aim, we generalize the concept of bipotential to dynamical systems. The keystone idea is to define a symplectic bipotential. We present a method to build it from a bipotential. Next, we generalize the symplectic Brezis-Ekeland-Nayroles principle to non associated dissipative laws. We apply it to the non associated plasticity and to the unilateral contact law with Coulomb's dry friction.

math.DS↗

arXiv2024

Which symmetry group for elementary particles with an electric charge today and in the past?

In this paper, we revisit the Kaluza-Klein theory from the perspective of the classification of elementary particles based on the coadjoint orbit method. We study the momentum map of the corresponding symmetry group $G_1$ which conserves the hyperbolic metric. We show that the electric charge is not frame-invariant, in contradiction with the experimental observations. In other words, it is not the symmetry group of the Universe today as we know it. To avert this paradox, we scale the fifth coordinate and consider the limit when the cylinder radius vanishes. For the corresponding group $G_0$, the charge is invariant. On this ground, we propose a cosmological scenario in which the elementary particles of the early Universe are classified from the momenta of the group $G_1$, next the three former dimensions inflate quickly while the fifth one shrinks, leading to the 4D era in which as today the particles are characterized by the momenta of the group $G_0$. By this mechanism, the elementary particles can acquire electric charge as a by-product of the 4 + 1 symmetry breaking of the Universe. This work opens the way to the geometric quantization of charged elementary particles. We construct the corresponding $G_0$-connections by pullback on the space-time. Imposing that the linear 5-momentum is parallel-transported, we recover the conservation of the charge and the equation of motion with Lorentz force. We revisit the variational relativity and obtain the field equations for both the gravitation and electromagnetic interactions with coupling terms which are negligible at the Newtonian approximation, allowing to recover Maxwell equations.

math-ph↗

arXiv2023

Symplectic and variational formulations of compressible and incompressible Navier-Stokes equation

In a previous paper, we proposed a symplectic version of Brezis-Ekeland-Nayroles principle based on the concepts of Hamiltonian inclusions and symplectic polar functions. We illustrated it by application to the standard plasticity in small deformations. The object of this work is to generalize the previous formalism to dissipative media in large deformations and Eulerian description. This aim is reached in three steps. Firstly, we develop a Lagrangian formalism for the reversible media based on the calculus of variation by jet theory. Next, we propose a corresponding Hamiltonian formalism for such media. Finally, we deduce from it a symplectic minimum principle for dissipative media and we show how to obtain a minimum principle for unstationary compressible and incompressible Navier-Stokes equation.

math-ph↗

arXiv2023

Presentation of Jean-Marie Souriau's book ''Structure des systèmes dynamiques''

Jean-Marie Souriau's book ''Structure des systèmes dynamiques'', published in 1970, republished recently by Gabay, translated in English and published under the title ''Structure of Dynamical Systems, a Symplectic View of Physic'', is a work with an exceptional wealth which, fifty years after its publication, is still topical. In this paper, we give a rather detailled description of its content and we intend to highlight the ideas that to us, are the most creative and promising.

math.DS↗

arXiv2021

A non incremental variational principle for brittle fracture

The aim of the paper is to propose a paradigm shift for the variational approach of brittle fracture. Both dynamics and the limit case of statics are treated in a same framework. By contrast with the usual incremental approach, we use a space-time principle covering the whole loading and crack evolution. The emphasis is given on the modelling of the crack extension by the internal variable formalism and a dissipation potential as in plasticity, rather than Griffith's original approach based on the surface area. The new formulation appears to be more fruitful for generalization than the standard theory.

cond-mat.mtrl-sci↗

arXiv2021

Constructing the Hamiltonian from the behaviour of a dynamical system by proper symplectic decomposition

The modal analysis is revisited through the symplectic formalism, what leads to two intertwined eigenproblems. Studying the properties of the solutions, we prove that they form a canonical basis. The method is general and works even if the Hamiltonian is not the sum of the potential and kinetic energies. On this ground, we want to address the following problem: data being given in the form of one or more structural evolutions, we want to construct an approximation of the Hamiltonian from a covariant snapshot matrix and to perform a symplectic decomposition. We prove the convergence properties of the method when the time discretization is refined. If the data cloud is not enough rich, we extract the principal component of the Hamiltonian corresponding to the leading modes, allowing to perform a model order reduction for very high dimension models. The method is illustrated by a numerical example.

physics.class-ph↗

arXiv2020

Post-Newtonian expansion with Galilean covariance

The Galilean gravitation derives from a scalar potential and a vector one. Poisson's equation to determine the scalar potential has no the expected Galilean covariance. Moreover, there are three missing equations to determine the potential vector. Besides, we require they have the Galilean covariance. These are the issues addressed in the paper. To avoid the drawbacks of the PPN approach and the NCT, we merge them into a new framework. The key idea is to take care that every term of the c expansion of the fields are Galilean covariants or invariants. The expected equations are deduced by variation of the Hilbert-Einstein functional. The contribution of the matter to the functional is derived from Souriau's conformation tensor. We obtain a system of four non linear equations, solved by asymptotic expansion.

gr-qc↗