Hamiltonian Description of Composite Fermions: Magnetoexciton Dispersions

A microscopic Hamiltonian theory of the FQHE, developed by Shankar and myself based on the fermionic Chern-Simons approach, has recently been quite successful in calculating gaps in Fractional Quantum Hall states, and in predicting approximate scaling relations between the gaps of different fractions. I now apply this formalism towards computing magnetoexciton dispersions (including spin-flip dispersions) in the $\nu=1/3$, 2/5, and 3/7 gapped fractions, and find approximate agreement with numerical results. I also analyse the evolution of these dispersions with increasing sample thickness, modelled by a potential soft at high momenta. New results are obtained for instabilities as a function of thickness for 2/5 and 3/7, and it is shown that the spin-polarized 2/5 state, in contrast to the spin-polarized 1/3 state, cannot be described as a simple quantum ferromagnet.Comment: 18 pages, 18 encapsulated ps figure

Light-induced modulated structures, intrinsic optical multistability and instabilities for the competitive wave interactions in liquid crystals

The multistability and temporal instabilities of nonlinear wave process with an energy transfer and competition between different light polarization components have been studied both theoretically and experimentally for a nonhomogeneous anisotropic medium with threshold nonlinearity. A feedback for such wave interactions, when the laser radiation induces the bulk-gratings of refractive index, arises because of the non-local response of the anisotropic elastic medium on the external field.On étudie à la fois théoriquement et expérimentalement la multistabilité et les instabilités temporelles de processus ondulatoires non linéaires dans les conditions de transfert d'énergie et de compétition entre les différentes composantes de polarisation, pour un milieu anisotrope inhomogène présentant une non-linéarité à seuil. Dans de telles interactions, il se produit un couplage rétroactif lorsque le rayonnement laser induit un réseau d'indice de réfraction dans le milieu, à cause de la réponse non locale du milieu élastique anisotrope au champ extérieur