On the role of ground state correlations in hypernuclear non-mesonic weak decay

The contribution of ground state correlations (GSC) to the non--mesonic weak decay of $^{12}_\Lambda$C and other medium to heavy hypernuclei is studied within a nuclear matter formalism implemented in a local density approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one-- and two--nucleon induced decays. Together with fermion antisymmetrization, GSC turn out to be important for an accurate determination of the decay widths. Besides opening the two--nucleon stimulated decay channels, for $^{12}_\Lambda$C GSC are responsible for 14% of the rate $\Gamma_1$ while increasing the $\Gamma_{n}/\Gamma_{p}$ ratio by 4%. Our final results for $^{12}_\Lambda$C are: $\Gamma_{\rm NM}=0.98$, $\Gamma_{n}/\Gamma_{p}=0.34$ and $\Gamma_2/\Gamma_{\rm NM}=0.26$. The saturation property of $\Gamma_{\rm NM}$ with increasing hypernuclear mass number is clearly observed. The agreement with data of our predictions for $\Gamma_{\rm NM}$, $\Gamma_n/\Gamma_p$ and $\Gamma_2$ is rather good.Comment: 32 pages, 9 figure

Studies of specific nuclear light bulb and open-cycle vortex stabilized gaseous nuclear rocket engines

Specific nuclear light bulb and open-cycle vortex stabilized gaseous nuclear rocket engine design

Interaction Effects in Conductivity of Si Inversion Layers at Intermediate Temperatures

We compare the temperature dependence of resistivity \rho(T) of Si MOSFETs with the recent theory by Zala et al. This comparison does not involve any fitting parameters: the effective mass m* and g*-factor for mobile electrons have been found independently. An anomalous increase of \rho with temperature, which has been considered a signature of the "metallic" state, can be described quantitatively by the interaction effects in the ballistic regime. The in-plane magnetoresistance \rho(B) is qualitatively consistent with the theory; however, the lack of quantitative agreement indicates that the magnetoresistance is more susceptible to the sample-specific effects than \rho(T).Comment: 4 pages, 5 figures. References update

Traveling waves of in vitro evolving RNA.

Populations of short self-replicating RNA variants have been confined to one side of a reaction-diffusion traveling wave front propagating along thin capillary tubes containing the Q beta viral enzyme. The propagation speed is accurately measurable with a magnitude of about 1 micron/sec, and the wave persists for hundreds of generations (of duration less than 1 min). Evolution of RNA occurs in the wavefront, as established by front velocity changes and gel electrophoresis of samples drawn from along the capillary. The high population numbers (approximately equal to 10(11], their well-characterized biochemistry, their short generation time, and the constant conditions make the system ideal for evolution experiments. Growth is monitored continuously by excitation of an added RNA-sensitive fluorescent dye, ethidium bromide. An analytic expression for the front velocity is derived for the multicomponent kinetic scheme that reduces, for a high RNA-enzyme binding constant, to the Fisher form v = 2 square root of kappa D, where D is the diffusion constant of the complex and kappa is the low-concentration overall replication rate coefficient. The latter is confirmed as the selective value-determining parameter by numerical solution of a two-species system

Factorization of e+e- Event Shape Distributions with Hadronic Final States in Soft Collinear Effective Theory

We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory.Comment: 21 pages. Journal version. Defined an explicit thrust axis operator; clarified meaning of a delta function operato

Phase Transitions in a Two-Component Site-Bond Percolation Model

A method to treat a N-component percolation model as effective one component model is presented by introducing a scaled control variable $p_{+}$. In Monte Carlo simulations on $16^{3}$, $32^{3}$, $64^{3}$ and $128^{3}$ simple cubic lattices the percolation threshold in terms of $p_{+}$ is determined for N=2. Phase transitions are reported in two limits for the bond existence probabilities $p_{=}$ and $p_{\neq}$. In the same limits, empirical formulas for the percolation threshold $p_{+}^{c}$ as function of one component-concentration, $f_{b}$, are proposed. In the limit $p_{=} = 0$ a new site percolation threshold, $f_{b}^{c} \simeq 0.145$, is reported.Comment: RevTeX, 5 pages, 5 eps-figure

Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films

The spin relaxation induced by the Elliott-Yafet mechanism and the extrinsic spin Hall conductivity due to the skew-scattering are investigated in 5d transition-metal ultrathin films with self-adatom impurities as scatterers. The values of the Elliott-Yafet parameter and of the spin-flip relaxation rate reveal a correlation with each other that is in agreement with the Elliott approximation. At 10-layer thickness, the spin-flip relaxation time in 5d transition-metal films is quantitatively reported about few hundred nanoseconds at atomic percent which is one and two orders of magnitude shorter than that in Au and Cu thin films, respectively. The anisotropy effect of the Elliott-Yafet parameter and of the spin-flip relaxation rate with respect to the direction of the spin-quantization axis in relation to the crystallographic axes is also analyzed. We find that the anisotropy of the spin-flip relaxation rate is enhanced due to the Rashba surface states on the Fermi surface, reaching values as high as 97% in 10-layer Hf(0001) film or 71% in 10-layer W(110) film. Finally, the spin Hall conductivity as well as the spin Hall angle due to the skew-scattering off self-adatom impurities are calculated using the Boltzmann approach. Our calculations employ a relativistic version of the first-principles full-potential Korringa-Kohn-Rostoker Green function method