We present an ab initio numerical many-body GW calculation of the band plot in free-standing graphene. We consider the full ionic and electronic structure introducing e-e interaction and correlation effects via a self-energy containing non-hermitian and dynamical terms. With respect to the density-functional theory local-density approximation, the Fermi velocity is renormalized with an increase of 17%, in better agreement with the experiment. Close to the Dirac point the linear dispersion is modified by the presence of a kink, as observed in angle-resolved photoemission spectroscopy. We demonstrate that the kink is due to low-energy π → π * single-particle excitations and to the π plasmon. The GW self-energy does not open the band gap.PACS numbers: 71.45.Gm, 79.20.Uv, The discovery of graphene by micromechanical cleavage [1, 2] and epitaxial grow [3] has attracted tremendous interest in consideration of its unusual electronic properties. In the tight-binding (TB) formalism, the graphene 2D honeycomb lattice structure gives rise to a semiconductor with zero band gap occurring at the K point in the Brillouin zone and a cone-like linear band-dispersion at low energy. This part is usually described by a massless Dirac (Weyl) dispersion [4]. Ab initio density-functional theory (DFT) calculations [5] confirm the TB linear dispersion picture and give an estimate of the Fermi velocity v F lower by 15∼20% than the experimental value. Recently, two angle-resolved photoemission spectroscopy (ARPES) experiments on graphene epitaxially grown on SiC [6,7,8,9, 10] raised the general interest. The first one [6,9] observed at low energy a nearly linear band dispersion with slight deviations in the form of small kinks interpreted as due to many-body electron-electron (e-e) and electron-phonon (e-ph) self-energy effects. The second one [7,8,10] provided a different picture, with the opening of a band gap occurring at the Dirac K point and attributed either to substrate (SiC) or to many-body selfenergy effects. A DFT calculation [11] seemed to confirm a substrate induced symmetry breaking, but recent STM measures [12] provided some evidence to exclude it. This situation calls for clarification about the role of e-e selfenergy effects on the quasiparticle (QP) band plot, the Fermi velocity and the band gap opening. Previous ab initio works have dealt with e-ph effects [5,13] and with e-e GW effects in graphene nanoribbons [14]. There are also several non ab initio works [15,16,17,18] which studied e-e self-energy effects in a 2D massless Dirac model.In this work we calculate the band plot of free-standing undoped graphene introducing e-e interaction and correlation effects by an ab initio many-body GW selfenergy [19,20]. We numerically simulate the full ionic and electronic structure of real graphene. We take into account the full dynamical dependence and nonhermiticity of the self-energy by an accurate contourdeformation (CD) integration. From the self-energy we then obtain the QP energies and the spectral function which can be di...

We evaluate the decays B → K * π, K(ρ, ω, φ) adding the long distance charming penguin contributions to the short distance: Tree+Penguin amplitudes. We estimate the imaginary part of the charming penguin by an effective field theory inspired by the Heavy Quark Effective Theory and parameterize its real part. The final results for branching ratios depend on only two real parameters and show a significant role of the charming penguins. The overall agreement with the available experimental data is satisfactory.

The aim of this work was to investigate the structural features of type I collagen isoforms and collagen-based films at atomic and molecular scales, in order to evaluate whether and to what extent different protocols of slurry synthesis may change the protein structure and the final properties of the developed scaffolds. Wide Angle X-ray Scattering data on raw materials demonstrated the preferential orientation of collagen molecules in equine tendon-derived collagens, while randomly oriented molecules were found in bovine skin collagens, together with a lower crystalline degree, analyzed by the assessment of FWHM (Full Width at Half Maximum), and a certain degree of salt contamination. WAXS and FT-IR (Fourier Transform Infrared) analyses on bovine collagen-based films, showed that mechanical homogenization of slurry in acidic solution was the treatment ensuring a high content of super-organization of collagen into triple helices and a high crystalline domain into the material. In vitro tests on rat Schwannoma cells showed that Schwann cell differentiation into myelinating cells was dependent on the specific collagen film being used, and was found to be stimulated in case of homogenization-treated samples. Finally DHT/EDC crosslinking treatment was shown to affect mechanical stiffness of films depending on collagen source and processing conditions.

We present calculations of the charming-penguin long-distance contributions to B→K decays due to intermediate charmed meson states. Our calculation is based on the chiral effective Lagrangian for light and heavy mesons, corrected for the hard pion and kaon momenta. We find that the charming-penguin contributions increase significantly the B→K decay rates in comparison with the short-distance contributions, giving results in better agreement with experimental data.