Maxwell's equations as a special case of deformation of a solid lattice in Euler's coordinates

It is shown that the set of equations known as Maxwell's equations perfectly describe two very different systems: (1) the usual electromagnetic phenomena in vacuum or in the matter and (2) the deformation of isotropic solid lattices, containing topological defects as dislocations and disclinations, in the case of constant and homogenous expansion. The analogy between these two physical systems is complete, as it is not restricted to one of the two Maxwell's equation couples in the vacuum, but generalized to the two equation couples as well as to the diverse phenomena of dielectric polarization and magnetization of matter, just as to the electrical charges and the electrical currents. The eulerian approach of the solid lattice developed here includes Maxwell's equations as a special case, since it stems from a tensor theory, which is reduced to a vector one by contraction on the tensor indices. Considering the tensor aspect of the eulerian solid lattice deformation theory, the analogy can be extended to other physical phenomena than electromagnetism, a point which is shortly discussed at the end of the paper.Comment: 20 pages, 4 figures, 2 table

Scaled Spectroscopy of 1Se and 1Po Highly Excited States of Helium

In this paper, we examine the properties of the 1Se and 1Po states of helium, combining perimetric coordinates and complex rotation methods. We compute Fourier transforms of quantities of physical interest, among them the average of the operator cos(theta_12), which measures the correlation between the two electrons. Graphs obtained for both 1Se and 1Po states show peaks at action of classical periodic orbits, either "frozen planet" orbit or asymmetric stretch orbits. This observation legitimates the semiclassical quantization of helium with those orbits only, not just for S states but also for P states, which is a new result. To emphasize the similarity between the S and P states we show wavefunctions of 1Po states, presenting the same structure as 1Se states, namely the "frozen planet" and asymmetric stretch configurations.Comment: revtex 15 pages with 6 figures, 2 figures (large) are available on request at email address [email protected]. to appear in J. Phys. B (April 98

Topological quantum phase transitions of attractive spinless fermions in a honeycomb lattice

We investigate a spinless Fermi gas trapped in a honeycomb optical lattice with attractive nearest-neighbor interactions. At zero temperature, mean-field theory predicts three quantum phase transitions, two being topological. At low interactions, the system is semi-metallic. Increasing the interaction further, the semi-metal destabilizes into a fully gapped superfluid. At larger interactions, a topological transition occurs and this superfluid phase becomes gapless, with Dirac-like dispersion relations. Finally, increasing again the interaction, a second topological transition occurs and the gapless superfluid is replaced by a different fully gapped superfluid phase. We analyze these different quantum phases as the temperature and the lattice filling are varied.Comment: 6 pages, 5 figure

L’insertion des diplômés des HEP en Suisse romande et au Tessin: premiers résultats d’une recherche en cours

"Enseignants débutants", "néotitulaires", "novices", "nouveaux diplômés"… quel que soit le terme qui les définisse, cette nouvelle génération d’enseignants aiguise la curiosité des chercheurs. Qui sont-ils? Quelles stratégies développent-ils pour s’insérer dans la société? Leur formation initiale correspond-elle à leurs besoins? Dans la perspective d’analyser l’insertion professionnelle des nouveaux enseignants formés dans les Hautes écoles pédagogiques, une enquête interinstitutionnelle se propose de décrire le contexte professionnel des enseignants ayant débuté dans la profession durant ces trois dernières années