Reduced Density Matrix Approach to Phononic Dissipation in Friction

Understanding mechanisms for energy dissipation from nanoparticles in contact with large samples is a central problem in describing friction microscopically. Calculation of the reduced density matrix appears to be the most suitable metho to study such systems that are coupled to a large environment. In this paper the time evolution of the reduced density matrix has been evaluated for an arbitrary system coupled to a heat reservoir. The formalism is then applied to study the vibrational relaxation following the stick-slip motion of a small adsorbate on a surface. The frequency dependence of the relaxation time is also determined.Comment: 16 pages, 3 figures (included), revte

A Global Treatment Of VMD Physics Up To The ϕ\phi: I. e+e−e^+e^- Annihilations, Anomalies And Vector Meson Partial Widths

The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3) symmetry and an isospin symmetry breaking leading naturally to vector meson mixing, has been recently shown to successfully account for e^+ e^- \ra \pi^+\pi^- cross section and for the dipion spectrum in $\tau$ decay. The present study shows that the full anomalous sector of the HLS model can be considered and is validated by the experimental data. Indeed, this extended model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^- data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^- \ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown that the fit of these data sets also predicts an accurate description of the \eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the reported information on their branching fractions and spectra. Finally, one also derives from our global fits products of widths of the form \Gamma (V \ra f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma (V \ra f_2) describing decays of vector mesons to several non--leptonic final states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change

Mars surface transportation options

As the number of scientific experiments for the surface of Mars grows, the need for effective surface transportation becomes critical. Because of the diversity of the experiments proposed, as well as the desire to explore Mars from the equator to the poles, the optimum surface vehicle configuration is not obvious. Five candidate vehicles are described, with an estimate of their size and performance. In order to maximize the success of a manned Mars mission, it appears that two vehicles should be designed for surface transportation: an advanced long-range rover, and a remotely-piloted airplane

A Global Treatment Of VMD Physics Up To The ϕ\phi: I. e+e−e^+e^- Annihilations, Anomalies And Vector Meson Partial Widths

The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3) symmetry and an isospin symmetry breaking leading naturally to vector meson mixing, has been recently shown to successfully account for e^+ e^- \ra \pi^+\pi^- cross section and for the dipion spectrum in $\tau$ decay. The present study shows that the full anomalous sector of the HLS model can be considered and is validated by the experimental data. Indeed, this extended model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^- data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^- \ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown that the fit of these data sets also predicts an accurate description of the \eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the reported information on their branching fractions and spectra. Finally, one also derives from our global fits products of widths of the form \Gamma (V \ra f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma (V \ra f_2) describing decays of vector mesons to several non--leptonic final states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change

Can VMD improve the estimate of the muon g-2 ?

We show that a VMD based theoretical input allows for a significantly improved accuracy for the hadronic vacuum polarization of the photon which contributes to the theoretical estimate of the muon g-2. We also show that the only experimental piece of information in the $\tau$ decay which cannot be accounted for is the accepted value for {\rm Br}(\tau \ra \pi \pi \nu_\tau), while the spectum lineshape is in agreement with expectations from $e^+ e^-$ annihilations.Comment: 6 pages, 1 figure Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, Chin

A sub-product construction of Poincare-Einstein metrics

Given any two Einstein (pseudo-)metrics, with scalar curvatures suitably related, we give an explicit construction of a Poincar\'e-Einstein (pseudo-)metric with conformal infinity the conformal class of the product of the initial metrics. We show that these metrics are equivalent to ambient metrics for the given conformal structure. The ambient metrics have holonomy that agrees with the conformal holonomy. In the generic case the ambient metric arises directly as a product of the metric cones over the original Einstein spaces. In general the conformal infinity of the Poincare metrics we construct is not Einstein, and so this describes a class of non-conformally Einstein metrics for which the (Fefferman-Graham) obstruction tensor vanishes.Comment: 23 pages Minor correction to section 5. References update

Pseudoscalar-scalar transition form factors in covariant light front dynamics

In an explicitly covariant light-front formalism, we analyze transition form factors between pseudoscalar and scalar mesons. Application is performed in case of the $B \to f_0(980)$ transition in the full available transfer momentum range $q^2$.Comment: 4 pages, 4 figures. Talk given at the XXXIII International Conference on High Energy Physics, ICHEP06, Moscow, 26 July-02 Augus