Electron-phonon coupling in metallic carbon nanotubes: Dispersionless electron propagation despite dissipation

A recent study [Rosati, Dolcini, and Rossi, Appl. Phys. Lett. 106, 243101 (2015)] has predicted that, while in semiconducting single-walled carbon nanotubes (SWNTs) an electronic wave packet experiences the typical spatial diffusion of conventional materials, in metallic SWNTs its shape remains essentially unaltered up to micron distances at room temperature, even in the presence of the electron-phonon coupling. Here, by utilizing a Lindblad-based density-matrix approach enabling us to account for both dissipation and decoherence effects, we test such prediction by analyzing various aspects that were so far unexplored. In particular, accounting for initial nonequilibrium excitations, characterized by an excess energy $E_0$, and including both intra- and interband phonon scattering, we show that for realistically high values of $E_0$ the electronic diffusion is extremely small and nearly independent of its energetic distribution, in spite of a significant energy-dissipation and decoherence dynamics. Furthermore, we demonstrate that the effect is robust with respect to the variation of the chemical potential. Our results thus suggest that metallic SWNTs are a promising platform to realise quantum channels for the non-dispersive transmission of electronic wave packets.Comment: 14 pages, 7 figure

Quintessential Enhancement of Dark Matter Abundance

The presence of a dynamical scalar field in the early universe could significantly affect the `freeze-out' time of particle species. In particular, it was recently shown that an enhancement of the relic abundance of neutralinos can be produced in this way. We examine under which conditions this primordial scalar field could be identified with the Quintessence scalar and find, through concrete examples, that modifications to the standard paradigm are necessary. We discuss two possible variations: the presence of more scalars and the switching on of an interaction

Renormalization Group Approach to Spin Glass Systems

A renormalization group transformation suitable for spin glass models and, more generally, for disordered models, is presented. The procedure is non-standard in both the nature of the additional interactions and the coarse graining transformation, that is performed on the overlap probability measure (which is clearly non-Gibbsian). Universality classes are thus naturally defined on a large set of models, going from $\Z_2$ and Gaussian spin glasses to Ising and fully frustrated models, and others.Comment: 12 pages, 4 figure

Weak proton capture on 3He

The astrophysical S-factor for the proton weak capture on 3He is calculated with correlated-hyperspherical-harmonics bound and continuum wave functions corresponding to realistic Hamiltonians consisting of the Argonne v14 or Argonne v18 two-nucleon and Urbana-VIII or Urbana-IX three-nucleon interactions. The nuclear weak charge and current operators have vector and axial-vector components, that include one- and many-body terms. All possible multipole transitions connecting any of the p 3He S- and P-wave channels to the 4He bound state are considered. The S-factor at a p 3He center-of-mass energy of 10 keV, close to the Gamow-peak energy, is predicted to be 10.1 10^{-20} keV b with the AV18/UIX Hamiltonian, a factor of about 4.5 larger than the value adopted in the standard solar model. The P-wave transitions are found to be important, contributing about 40 % of the calculated S-factor. The energy dependence is rather weak: the AV18/UIX zero-energy S-factor is 9.64 10^{-20} keV b, only 5 % smaller than the 10 keV result quoted above. The model dependence is also found to be weak: the zero-energy S-factor is calculated to be 10.2 10^{-20} keV b with the older AV14/UVIII model, only 6 % larger than the AV18/UIX result. Our best estimate for the S-factor at 10 keV is therefore (10.1 \pm 0.6) 10^{-20} keV b, when the theoretical uncertainty due to the model dependence is included. This value for the calculated S-factor is not as large as determined in fits to the Super-Kamiokande data in which the hep flux normalization is free. However, the precise calculation of the S-factor and the consequent absolute prediction for the hep neutrino flux will allow much greater discrimination among proposed solar neutrino oscillation solutions.Comment: 54 pages RevTex file, 6 PostScript figures, submitted to Phys. Rev.

SUSY QCD and Quintessence

Recent data point in the direction of a cosmological constant dominated universe. We investigate the role of supersymmetric QCD with N_f 1, the multiscalar dynamics is fully taken into account, showing that a certain degree of flavor symmetry in the initial conditions is necessary in order to attain the required late-time ``tracking'' attractor behavior. A possible solution to the problem of long-range interactions of gravitational strength is proposed. Finally we show how, as a consequence of the interaction with the Standard Model fields, the early cosmological evolution of the scalar fields may be dramatically altered, and the approach to the tracking behavior may become much more efficient

Theoretical Estimation of CO2 Compression and Transport Costs for an Hypothetical Carbon and Capture & Storage Requalification of the Saline Joniche Power Plant Project

SEI S.p.a. presented a project to build a 1320 MW coal-fired power plant in Saline Joniche, on the Southern tip of Calabria Region, Italy, in 2008. A gross early evaluation about the possibility to add CCS (CO2 Capture & Storage) was performed too. The project generated widespread opposition among environmental associations, citizens and local institutions in that period, against the coal use to produce energy, as a consequence of its GHG clima-alterating impact. Moreover the CCS (also named Carbon Capture & Storage or more recently CCUS: Carbon Capture-Usage-Storage) technology was at that time still an unknown and “mysterious” solution for the GHG avoiding to the atmosphere.   The present study concerns the sizing of the compression and transportation system of the CCS section, included in the project presented at the time by SEI Spa; the sizing of the compression station and the pipeline connecting the plant to the possible Fosca01 offshore injection site previously studied as a possible storage solution, as part of a coarse screening of CO2 storage sites in the Calabria Region. This study takes into account the costs of construction, operation and maintenance (O&M) of both the compression plant and the sound pipeline, considering the gross static storage capacity of the Fosca01 reservoir as a whole as previously evaluated