Tunneling through magnetic molecules with arbitrary angle between easy axis and magnetic field

Inelastic tunneling through magnetically anisotropic molecules is studied theoretically in the presence of a strong magnetic field. Since the molecular orientation is not well controlled in tunneling experiments, we consider arbitrary angles between easy axis and field. This destroys all conservation laws except that of charge, leading to a rich fine structure in the differential conductance. Besides single molecules we also study monolayers of molecules with either aligned or random easy axes. We show that detailed information on the molecular transitions and orientations can be obtained from the differential conductance for varying magnetic field. For random easy axes, averaging over orientations leads to van Hove singularities in the differential conductance. Rate equations in the sequential-tunneling approximation are employed. An efficient approximation for their solution for complex molecules is presented. The results are applied to Mn12-based magnetic molecules.Comment: 10 pages, 10 figures include

Travelling waves in hyperbolic chemotaxis equations

Mathematical models of bacterial populations are often written as systems of partial differential equations for the densities of bacteria and concentrations of extracellular (signal) chemicals. This approach has been employed since the seminal work of Keller and Segel in the 1970s [Keller and Segel, J. Theor. Biol., 1971]. The system has been shown to permit travelling wave solutions which correspond to travelling band formation in bacterial colonies, yet only under specific criteria, such as a singularity in the chemotactic sensitivity function as the signal approaches zero. Such a singularity generates infinite macroscopic velocities which are biologically unrealistic. In this paper, we formulate a model that takes into consideration relevant details of the intracellular processes while avoiding the singularity in the chemotactic sensitivity. We prove the global existence of solutions and then show the existence of travelling wave solutions both numerically and analytically

Scheme for sharing classical information via tripartite entangled states

We investigate schemes for quantum secret sharing and quantum dense coding via tripartite entangled states. We present a scheme for sharing classical information via entanglement swapping using two tripartite entangled GHZ states. In order to throw light upon the security affairs of the quantum dense coding protocol, we also suggest a secure quantum dense coding scheme via W state in analogy with the theory of sharing information among involved users.Comment: 4 pages, no figure. A complete rewrritten vession, accepted for publication in Chinese Physic

Microscopic theory of single-electron tunneling through molecular-assembled metallic nanoparticles

We present a microscopic theory of single-electron tunneling through metallic nanoparticles connected to the electrodes through molecular bridges. It combines the theory of electron transport through molecular junctions with the description of the charging dynamics on the nanoparticles. We apply the theory to study single-electron tunneling through a gold nanoparticle connected to the gold electrodes through two representative benzene-based molecules. We calculate the background charge on the nanoparticle induced by the charge transfer between the nanoparticle and linker molecules, the capacitance and resistance of molecular junction using a first-principles based Non-Equilibrium Green's Function theory. We demonstrate the variety of transport characteristics that can be achieved through ``engineering'' of the metal-molecule interaction.Comment: To appear in Phys. Rev.

Triaxially deformed relativistic point-coupling model for Λ\Lambda hypernuclei: a quantitative analysis of hyperon impurity effect on nuclear collective properties

The impurity effect of hyperon on atomic nuclei has received a renewed interest in nuclear physics since the first experimental observation of appreciable reduction of $E2$ transition strength in low-lying states of hypernucleus $^{7}_\Lambda$Li. Many more data on low-lying states of $\Lambda$ hypernuclei will be measured soon for $sd$-shell nuclei, providing good opportunities to study the $\Lambda$ impurity effect on nuclear low-energy excitations. We carry out a quantitative analysis of $\Lambda$ hyperon impurity effect on the low-lying states of $sd$-shell nuclei at the beyond-mean-field level based on a relativistic point-coupling energy density functional (EDF), considering that the $\Lambda$ hyperon is injected into the lowest positive-parity ($\Lambda_s$) and negative-parity ($\Lambda_p$) states. We adopt a triaxially deformed relativistic mean-field (RMF) approach for hypernuclei and calculate the $\Lambda$ binding energies of hypernuclei as well as the potential energy surfaces (PESs) in $(\beta, \gamma)$ deformation plane. We also calculate the PESs for the $\Lambda$ hypernuclei with good quantum numbers using a microscopic particle rotor model (PRM) with the same relativistic EDF. The triaxially deformed RMF approach is further applied in order to determine the parameters of a five-dimensional collective Hamiltonian (5DCH) for the collective excitations of triaxially deformed core nuclei. Taking $^{25,27}_{\Lambda}$Mg and $^{31}_{\Lambda}$Si as examples, we analyse the impurity effects of $\Lambda_s$ and $\Lambda_p$ on the low-lying states of the core nuclei...Comment: 15 pages with 18 figures and 1 table (version to be published in Physical Review C

Black hole mass and accretion rate of active galactic nuclei with double-peaked broad emission lines

(Abridged) Using an empirical relation between the broad line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 AGNs with double-peaked broad emission lines in two samples. With black hole masses from $3\times 10^7M_\odot$ to $5\times 10^9M_\odot$, these AGNs have the dimensionless accretion rates (Eddington ratios) between 0.001 and 0.1, and the bolometric luminosity between $10^{43}erg/s$ and $10^{46}erg/s$, both being significantly larger than those of several previously known low-luminosity double-peaked AGNs. The optical-X-ray spectra indices, $\alpha_{OX}$, of these high-luminosity double-peaked AGNs is between 1 and 1.9. Modest correlations of the $\alpha_{OX}$ value with the Eddington ratio and bolometric luminosity indicate that double-peaked AGNs with higher Eddington ratio or higher luminosity tend to have larger $\alpha_{OX}$ value. Therefore we suggested that the accretion process in some high-luminosity double-peaked AGNs is probably different from that of low-luminosity objects where an ADAF-like accretion flow was thought to exist. This is also supported by the presence of possible big blue bumps in the spectra of some double-peaked AGNs with higher Eddington ratios. We noticed that the prototype double-peaked emission line AGN, Arp 102B, may be an ``intermediate'' object between the high and low luminosity double-peaked AGNs. In addition, we found an apparent strong anti-correlation between the peak separation of double-peaked profile and Eddington ratio. If it is real, it may provide us a clue to understand why double-peaked broad emission lines were hardly found in luminous AGNs with Eddington ratio larger than 0.1.Comment: 24 pages, 6 figures, accepted by Ap

Response of Alluvial Valleys to Incident SH, SV and P Waves

Results of an extensive numerical study on two dimensional wave scattering by valleys of semi-elliptical cross section due to incident SH, SV and P waves are presented. The investigation has been conducted using a rigorous Boundary element algorithm. The influence of key parameters, such as, valley depth, impedance ratio, frequency, and angle of incidence on surface ground motion are studied in detail. Furthermore, the case of a valley within a layered half space is analyzed and results compared with those obtained for a valley within a homogeneous half space