Gamow-Teller strength distributions for double-beta-decaying nuclei within continuum-QRPA

A version of the pn-continuum-QRPA is outlined and applied to describe the Gamow-Teller strength distributions for $\beta\beta$-decaying open-shell nuclei. The calculation results obtained for the pairs of nuclei $^{116}$Cd-Sn and $^{130}$Te-Xe are compared with available experimental data.Comment: 8 pages, 3 figures, To appear in the proceedings of "Nucleus-2007: Fundamental problems of nuclear physics, atomic power engineering and nuclear technologies" Voronezh, Russia, June 25-29, 200

Uncertainty in the 0νββ decay nuclear matrix elements

The nuclear matrix elements M0nu of the neutrinoless double-beta decay (0nubetabeta) are evaluated for 76Ge,100Mo,130Te, and 136Xe within the renormalized quasiparticle random phase approximation (RQRPA) and the simple QRPA. Three sets of single particle level schemes are used, ranging in size from 9 to 23 orbits. When the strength of the particle-particle interaction is adjusted so that the 2nubetabeta decay rate is correctly reproduced, the resulting M0nu values become essentially independent of the size of the basis, and of the form of different realistic nucleon-nucleon potentials. Thus, one of the main reasons for variability of the calculated M0nu within these methods is eliminated

Apparent power-law behavior of conductance in disordered quasi-one-dimensional systems

Dependence of hopping conductance on temperature and voltage for an ensemble of modestly long one-dimensional wires is studied numerically using the shortest-path algorithm. In a wide range of parameters this dependence can be approximated by a power-law rather than the usual stretched-exponential form. Relation to recent experiments and prior analytical theory is discussed.Comment: 5 pages, 3 figures. Comparison with prior theoretical and experimental work was extende

On The Existence of Planets Around the Pulsar PSR B0329+54

Results of timing measurements of the pulsar PSR B0329+54 obtained in 1968--2012 using the Big Scanning Antenna of the Pushchino Radio Astronomy Observatory (at 102 and 111 MHz), the DSS 13 and DSS 14 telescopes of the Jet Propulsion Laboratory (2388 MHz), and the 64 m telescope of the Kalyazin Radio Astronomy Observatory (610 MHz) are presented. The astrometric and rotational parameters of the pulsar are derived at a new epoch. Periodic variations in the barycentric timing residuals have been found, which can be explained by the presence of a planet orbiting the pulsar, with an orbital period $P_{1}$ = 27.8 yr, mass \textit{$m_{c}$}sin\textit{i} = 2$M_{\oplus}$, and orbital semi-major axis $a$ = 10.26 AU. The results of this study do not confirm existence of a proposed second planet with orbital period $P_{2}$ = 3 yr.Comment: 11 pages, 3 figures, to be published in Astronomy Reports, Nov. 201

Double Beta Decay, Nuclear Structure and Physics beyond the Standard Model

Neutrinoless Double Beta Decay ($0\nu\beta\beta$) is presently the only known experiment to distinguisch between Dirac neutrinos, different from their antiparticles, and Majorana neutrinos, identical with their antiparticles. In addition $0\nu\beta\beta$ allows to determine the absolute scale of the neutrino masses. This is not possible with neutrino oscillations. To determine the neutrino masses one must assume, that the light Majorana neutrino exchange is the leading mechanism for $0\nu\beta\beta$ and that the matrix element of this transition can ba calculated reliably. The experimental $0\nu\beta\beta$ transition amplitude in this mechanism is a product of the light left handed effective Majorana neutrino mass and of this transition matrix element. The different methods, Quasi-particle Random Phase Approximation (QRPA), Shell Model (SM), Projected Hartree-Fock-Bogoliubov (PHFB) and Interacting Boson Model (IBM2) used in the literature and the reliability of the matrix elements in these approaches are reviewed. In the second part it is investigated how one can determine the leading mechanism or mechanisms from the data of the $0\nu\beta\beta$ decay in different nuclei. Explicite expressions are given for the transition matrix elements. is shown, that possible interference terms allow to test CP (Charge and Parity conjugation) violation.Comment: Contribution to the EPS conference in Eilath: "Nuclear Physics in Astrophysics 5." April 3rd to 8th. 201

Excitons in anisotropic 2D semiconducting crystals

The excitonic behavior of anisotropic two-dimensional crystals is investigated using numerical methods. We employ a screened potential arising due to the system polarizability to solve the central-potential problem using the Numerov approach. The dependence of the exciton energies on the interaction strength and mass anisotropy is demonstrated. We use our results to obtain the exciton binding energy in phosphorene as a function of the substrate dielectric constant.Comment: 7 pages, 7 figure