J/ψ(ηc)NJ/\psi (\eta_c) N and Υ(ηb)N\Upsilon (\eta_b) N cross sections

Inspired by the recent findings of the two $P_c^+$ states in the $J/\psi p$ mass spectrum at LHCb, we investigate the elastic and inelastic cross sections of the $J/\psi N$, $\eta_c N$, $\Upsilon N$ and $\eta_b N$ channels within the constraints from heavy quark spin and flavour symmetry. The $\bar{D}^{(*)} \Sigma_c^{(*)}$ ($B^{(*)} \Sigma_b^{(*)}$) bound states predicted in earlier works should be accessible in elastic and/or inelastic processes of the $J/\psi N$ and/or $\eta_c N$ ($\Upsilon N$ and/or $\eta_b N$) interactions.Comment: Minor correction

Tunneling spectra of layered strongly correlated d-wave superconductors

Tunneling conductance experiments on cuprate superconductors exhibit a large diversity of spectra that appear in different nano-sized regions of inhomogeneous samples. In this letter, we use a mean-field approach to the tt't''J model in order to address the features in these spectra that deviate from the BCS paradigm, namely, the bias sign asymmetry at high bias, the generic lack of evidence for the Van Hove singularity, and the occasional absence of coherence peaks. We conclude that these features can be reproduced in homogeneous layered d-wave superconductors solely due to a proximate Mott insulating transition. We also establish the connection between the above tunneling spectral features and the strong renormalization of the electron dispersion around (0,pi) and (pi,0) and the momentum space anisotropy of electronic states observed in ARPES experiments.Comment: 4 pages, 3 figures. Added comment on the role of sample inhomogeneity. Published version. Homepage http://dao.mit.edu/~wen

On the canonical map of surfaces with q>=6

We carry out an analysis of the canonical system of a minimal complex surface of general type with irregularity q>0. Using this analysis we are able to sharpen in the case q>0 the well known Castelnuovo inequality K^2>=3p_g+q-7. Then we turn to the study of surfaces with p_g=2q-3 and no fibration onto a curve of genus >1. We prove that for q>=6 the canonical map is birational. Combining this result with the analysis of the canonical system, we also prove the inequality: K^2>=7\chi+2. This improves an earlier result of the first and second author [M.Mendes Lopes and R.Pardini, On surfaces with p_g=2q-3, Adv. in Geom. 10 (3) (2010), 549-555].Comment: Dedicated to Fabrizio Catanese on the occasion of his 60th birthday. To appear in the special issue of Science of China Ser.A: Mathematics dedicated to him. V2:some typos have been correcte

Flame Instability and Transition to Detonation in Supersonic Reactive Flows

Multidimensional numerical simulations of a homogeneous, chemically reactive gas were used to study ignition, flame stability, and deflagration-to-detonation transition (DDT) in a supersonic combustor. The configuration studied was a rectangular channel with a supersonic inflow of stoichiometric ethylene-oxygen and a transimissive outflow boundary. The calculation is initialized with a velocity in the computational domain equal to that of the inflow, which is held constant for the duration of the calculation. The compressible reactive Navier-Stokes equations were solved by a high-order numerical algorithm on an adapting mesh. This paper describes two calculations, one with a Mach 3 inflow and one with Mach 5.25. In the Mach 3 case, the fuel-oxidizer mixture does not ignite and the flow reaches a steady-state oblique shock train structure. In the Mach 5.25 case, ignition occurs in the boundary layers and the flame front becomes unstable due to a Rayleigh-Taylor instability at the interface between the burned and unburned gas. Growth of the reaction front and expansion of the burned gas compress and preheat the unburned gas. DDT occurs in several locations, initiating both at the flame front and in the unburned gas, due to an energy-focusing mechanism. The growth of the flame instability that leads to DDT is analyzed using the Atwood number parameter

New model of calculating the energy transfer efficiency for the spherical theta-pinch device

Ion-beam-plasma-interaction plays an important role in the field of Warm Dense Matter (WDM) and Inertial Confinement Fusion (ICF). A spherical theta pinch is proposed to act as a plasma target in various applications including a plasma stripper cell. One key parameter for such applications is the free electron density. A linear dependency of this density to the amount of energy transferred into the plasma from an energy storage was found by C. Teske. Since the amount of stored energy is known, the energy transfer efficiency is a reliable parameter for the design of a spherical theta pinch device. The traditional two models of energy transfer efficiency are based on assumptions which comprise the risk of systematical errors. To obtain precise results, this paper proposes a new model without the necessity of any assumption to calculate the energy transfer efficiency for an inductively coupled plasma device. Further, a comparison of these three different models is given at a fixed operation voltage for the full range of working gas pressures. Due to the inappropriate assumptions included in the traditional models, one owns a tendency to overestimate the energy transfer efficiency whereas the other leads to an underestimation. Applying our new model to a wide spread set of operation voltages and gas pressures, an overall picture of the energy transfer efficiency results

B\"{a}cklund transformations for the constrained dispersionless hierarchies and dispersionless hierarchies with self-consistent sources

The B\"{a}cklund transformations between the constrained dispersionless KP hierarchy (cdKPH) and the constrained dispersionless mKP hieararchy (cdmKPH) and between the dispersionless KP hieararchy with self-consistent sources (dKPHSCS) and the dispersionless mKP hieararchy with self-consistent sources (dmKPHSCS) are constructed. The auto-B\"{a}cklund transformations for the cdmKPH and for the dmKPHSCS are also formulated.Comment: 11 page

Doped carrier formulation and mean-field theory of the tt't''J model

In the generalized-tJ model the effect of the large local Coulomb repulsion is accounted for by restricting the Hilbert space to states with at most one electron per site. In this case the electronic system can be viewed in terms of holes hopping in a lattice of correlated spins, where holes are the carriers doped into the half-filled Mott insulator. To explicitly capture the interplay between the hole dynamics and local spin correlations we derive a new formulation of the generalized-tJ model where doped carrier operators are used instead of the original electron operators. This ``doped carrier'' formulation provides a new starting point to address doped spin systems and we use it to develop a new, fully fermionic, mean-field description of doped Mott insulators This mean-field approach reveals a new mechanism for superconductivity, namely spinon-dopon mixing, and we apply it to the tt't''J model as of interest to high-temperature superconductors. In particular, we use model parameters borrowed from band calculations and from fitting ARPES data to obtain a mean-field phase diagram that reproduces semi-quantitatively that of hole and electron doped cuprates. The mean-field approach hereby presented accounts for the local antiferromagnetic and d-wave superconducting correlations which, we show, provide a rational for the role of t' and t'' in strengthening superconductivity as expected by experiments and other theoretical approaches. As we discuss how t, t' and t'' affect the phase diagram, we also comment on possible scenarios to understand the differences between as-grown and oxygen reduced electron doped samples.Comment: 17 pages, 2 figures. Homepage http://dao.mit.edu/~wen