Optical Conductivity in Mott-Hubbard Systems

We study the transfer of spectral weight in the optical spectra of a strongly correlated electron system as a function of temperature and interaction strength. Within a dynamical mean field theory of the Hubbard model that becomes exact in the limit of large lattice coordination, we predict an anomalous enhancement of spectral weight as a function of temperature in the correlated metallic state and report on experimental measurements which agree with this prediction in $V_2O_3$. We argue that the optical conductivity anomalies in the metal are connected to the proximity to a crossover region in the phase diagram of the model.Comment: 12 pages and 4 figures, to appear in Phys. Rev. Lett., v 75, p 105 (1995

Observation of the Gap and Kinetic Energy in a Correlated Insulator

Fundamental energies are determined optically for an ensemble of correlated electrons in an anti-ferromagnetic insulator, V_2O_3. The observed variation of the energy gap and the kinetic energy are compared quantitatively to some approximate solutions of the Hubbard Hamiltonian

Oxydation et réduction d´explantats dorsaux et ventraux de gastrulas (amphibiens)

info:eu-repo/semantics/publishe

Recherches sur le rôle des groupes sulfhydriles dans la morphogénèse. I. Action des inhibiteurs des groupes SH sur l'oeuf entier et sur des explantats dorsaux et ventraux chez les amphibiens; implantation de protéines sulfhydrilées. II. Effect de quelques agents oxydants et réducteurs sur le développement d'explantats dorsaux et ventraux de jeunes gastrulas d'amphibiens.

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