Michel, Louis

Classification of the symmetries of ordinary differential equations
Conference given at the XIIIth International Colloquium on Group Theoretical Methods in Physics. Moscow, june 4-9, 1990

Abstract : We present S. Lie's work on the symmetry of ODE (ordinary differential equations) : action of Diff 2(x,y), the Lie…

Extrema of P-invariant functions on the Brillouin zone
Exapnded version of a lecture fiven at Naples, on October 25, 1991 at a Colloquium in memory of Léon Vanhove

Abstract : This paper studies the number of extrema (and their positions) of a countinuous Morse function on the Brillouin zone, when it…

D-E classification of the local extensions of su 2 current algebras
Abstract : A method is developed for constructing single valued rational 4-point functions of primary fields for su2 conformal current algebra satisfying the Knizhnik-Zamolodchikov equation. For integer conformal dimensions ? these rational solutions…

Bravais classes, Voronoï cells, Delone symbols
This text correspond to a set of lectures given at Third international school at Zajaceskowo (Poznan) Polane on Symmetry and structural Properties of condensed matter

Abstract : We give the most refined intrinsic classification of three…

Collapse of the Zeeman structure of the hydrogen atom in external electric field
Abstract : From Zeeman to Stark structure of a weakly split Rydberg n multiplet of the H atom in parallel magnetic and electric fields is analyzed. Classical mechanics together with topologiacl and group theoretical arguments enable us to describe in…

Physical implications of crystal symmetry and time reversal
Lectures given at the international school on Symmetry and Structural Properties of Condensed Matter. August 28 - September 5, 1996, Zajaczkowo (Posnan), Poland.

Wigner memorial lecture
Lecture given at Goslar (Germany) on july 16, 1996 to close the Wigner award ceremony during the 21st International Colloquium on Group Theoretical Methods in Physics

Complete description of the Voronoï cell of the Lie Algebras An weight lattice. On the Bounds for the number of d-faces of the n-dimensional Voronoï cells
Version étendue d'une conférence faite le 9 janvier 1997 au Centre de Recherches Mathématiques de l'Université de Montréal au cours du colloque pour le 60e anniversaire de Jiri Patera et Pavel Winternitz.

Abstract :Denoting these bounds by…

Rydberg states of atoms and molecules. Basic group theoretical and topological analysis
Abstract : Rydberg states of atoms and molecules are studied within the qualitative approach-based primarily on topological and group theoretical analysis. The correspondence between classical and quantum mechanics is explored to apply the results of…

Recent results on the implications of crystal symmetry and time reversal
Lecture given on August 1rst 1997 at the VIIIth International Conference on Symmetry Methods un Physics. JINR, Dubna, Russia.

Symmetry and topology of energy bands in crystals
Lecture given at the internation schoolon Symmetry abd Structural Properties of Condensed Matter. August 27 - September 2, 1998, Zajaczkowo (Posnan), Poland.

Constraints on spin rotation parameters due to isospin conservation
Abstract : We made a complete study of the relations between the three cross sections and the three sets of spin rotation parameters P, A, R for three reactions related by internal symmetry via two channels.

Some Remarks on polarization measurement and polarization domain
Abstract : We emphasize that any analysis of polarization measurement must be done in terms of the polarization domain which is much smaller than the domain of physical bounds. We propose a possible quantitative procedure to estimate the precision of…

Analysis of polarization measurements and test of selection rules and of models
Summer Study : High Energy with Polarized Beans, Argonne National Laboratory. Talk of Louis Michel (July 25, 1974)

Argone summer study High energy physics with polarized beams
Talk given by Louis Michel at the Workshop Acceleration and storage of Polarized Beams (July 25, 1974)

Test of models and polarization effects : the quark model
IIIrd International Winter Meeting on Fundamental Physics, Sierra Nevada (Granada, Sapin), February 15, 1975

Les Brisures spontanées de symétrie en physique
Conférence faite le 1erjuillet 1975 à Dijon, au congrès de la Société Française de Physique, à l'occasion de la réception du prix robin

Résumé. — Quelques remarques non scientifiques mais importantes. Notion de brisure spontanée

À Propos des brisures spontanées de symétrie
4th International Colloquium on Group Theoretical Methods in Physics, June 23-25, 1975

A Selection rule on angular momentum transfer in reactions of the type 0- (1+)/2 ?1- (3+)/2 <br /><br />
Abstract : An analysis of 50 expertmental data on polarization and correlations of polarization in the reactions ?N ~ ?, w?and KN ~ K*?, pE*, ??* strongly suggests a pure ?J = 1
transition at the baryon vertex. A plot for testing graphically the…

Static finite-energy solutions of Gauge fields with separated radial variable
Abstract : For arbitrary compact gauge group G and real representations of the Higgs fields, we seek static finite-energy solutions for which the radial dependence of the fields is factorized. We find that the gauge fields vanish outside a fixed…

Classification of topological stable defects in ordered media
Résumé. - Les défauts de symétrie d’un milieu ordonné qui sont topologiquement stables, sont classés par des groupes d’homotopie. A titre d’exemple, nous établissons une classification complète de ces défauts de symétrie…

Application of Morse theory to the symmetry breaking in the Landau theory of second order phase transition
Abstract : We treat here the case of all irreps (irreducible representations) on the reals of the 32 point groups. For each point group these irreps are irreps with wave vector k = 0 of the corresponding space groups. Landau model of second order…

Spontaneous breaking of Euclidean invariance oand classifications of topologically stable defects and configurations of crystals and crystals and liquid crystals
Abstract : We show how many mesomorphic states illustrate the following general scheme: The symmetry group of an equilibrium state of Euclidean-invariant quantum statistical mechanics is a subgroup H of the Euclidean group E such that the orbit E/H…

Analysis of ?1232 polarization
Abstract : The observed polarization domain of a spin 3/2 ? produced in a quasi two body or incluseve reaction is a sphere in three dimensions when the beam and the targert are unpolarized and a sphere in five dimensions otherwise. In the strong,…

The Description of the symmetry of physical states and spontaneous symmetry breaking
Lecture given on September 1st, 1980 at the Colloque Pierre Curie sur La Symetrie et les ruptures de sypétrie en phyisque de la matière condensée

The Symmetry and renormalization group fixed points of quadratic hamiltonians
Abstract : This paper studies the number and the nature of the fixed points of the renormalization group for the ?4 model, as used for instance in the Landau theory of second order phase transitions. It is shown that when it exists the stable fixed…

Représentation de vibration d&#039;un cristal construite par induction de représentations
Résumé : La représentation du groupe d'espcace GK d'un vecteur d'onde k est le produit tensoriel de la représentation vectorielle du groupe ponctuel Pk de k et d'une représentation induite donnée explicitement.
L'utilisation du théorème de…

The Structure of unitary representations of space groups
Lecture given by L. Michel at the XI-th International colloquium on Group Theoretical Methods in Physics at Istanbul, August 1982

Abstract : For systems with a symmetry group G, the description of physical phenomena corresponding to a…

Some Use of metabelian groups in physics
Abstract : Metabelian groups are those whose structure differ the least from Abelian groups. We explain the classification of finite metabelian groups and give some examples of physics problems where they play an important role.

Landau theory of second order phase transitions and invariant theory
Abstract : We give some basic concepts on group actions and theorems in invariant theory useful for the contrcution and the study of Landau polynomials. We apply them to the study of the isotropy groups of extrema of Landau polynomials. We explain…

Zeros of covariant vector fields for the point groups : Invariant formulation
Abstract. 2014 All finite as well as infinite (matrix) point subgroups of full orthogonal groups in two and three dimensions
are considered. For each point group a polynomial integrity basis for invariants and the basic polynomial vector fields are…