Inelastic x-ray scattering investigations of lattice dynamics in SmFeAsO1−x_{1-x}Fy_y superconductors

We report measurements of the phonon density of states as measured with inelastic x-ray scattering in SmFeAsO$_{1-x}$F$_y$ powders. An unexpected strong renormalization of phonon branches around 23 meV is observed as fluorine is substituted for oxygen. Phonon dispersion measurements on SmFeAsO$_{1-x}$F$_y$ single crystals allow us to identify the 21 meV A$_{1g}$ in-phase (Sm,As) and the 26 meV B$_{1g}$ (Fe,O) modes to be responsible for this renormalization, and may reveal unusual electron-phonon coupling through the spin channel in iron-based superconductors.Comment: 4 pages, 3 figures, submitted for SNS2010 conference proceeding

Gravitational hedgehog, stringy hedgehog and stringy sphere

We investigate the solutions of Einstein equations such that a hedgehog solution is matched to different exterior or interior solutions via a spherical shell. In the case where both the exterior and the interior regions are hedgehog solutions or one of them is flat, the resulting spherical shell becomes a stringy shell. We also consider more general matchings and see that in this case the shell deviates from its stringy character.Comment: 11 page

Casimir energy of the massless scalar field on S-1 by the point-splitting method

We calculate the Casimir energy of the massless scalar field on a one dimensional Riemann sphere (S-1) using the point-splitting method. We consider the full space, half space and an arc of arbitrary radius. This problem is interesting since it may be solved analytically be several renormalization techniques

Probing the Coulomb Interaction of PuCoGa by Phonon Spectroscopy

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Probing the Coulomb Interaction of the Unconventional Superconductor PuCoGa5 by Phonon Spectroscopy

The discovery of superconductivity in the plutonium based intermetallic compound PuCoGa5 came as a surprise with regard to the high transition temperature Tc 18,5 K for an actinide material [1].JRC.E.6-Actinides researc

Inelastic X-ray Scattering Investigations of Lattice Dynamics in SmFeAsO1-xFy Superconductors

We report measurements of the phonon density of states as measured with inelastic x-ray scattering in SmFeAsO{sub 1-x}F{sub y} powders. An unexpected strong renormalization of phonon branches around 23 meV is observed as fluorine is substituted for oxygen. Phonon dispersion measurements on SmFeAsO{sub 1-x}F{sub y} single crystals allow us to identify the 21 meV A{sub 1g} in-phase (Sm,As) and the 26 meV B{sub 1g} (Fe,O) modes to be responsible for this renormalization, and may reaveal unusual electron-phonon coupling through the spin channel in iron-based superconductors