Random-phase reservoir and a quantum resistor: The Lloyd model

We introduce phase disorder in a 1D quantum resistor through the formal device of `fake channels' distributed uniformly over its length such that the out-coupled wave amplitude is re-injected back into the system, but with a phase which is random. The associated scattering problem is treated via invariant imbedding in the continuum limit, and the resulting transport equation is found to correspond exactly to the Lloyd model. The latter has been a subject of much interest in recent years. This conversion of the random phase into the random Cauchy potential is a notable feature of our work. It is further argued that our phase-randomizing reservoir, as distinct from the well known phase-breaking reservoirs, induces no decoherence, but essentially destroys all interference effects other than the coherent back scattering.Comment: 4 pages,5 figure

On Higher Derivatives as Constraints in Field Theory: a Geometric Perspective

We formalize geometrically the idea that the (de Donder) Hamiltonian formulation of a higher derivative Lagrangian field theory can be constructed understanding the latter as a first derivative theory subjected to constraints.Comment: 7 page

Decohering d-dimensional quantum resistance

The Landauer scattering approach to 4-probe resistance is revisited for the case of a d-dimensional disordered resistor in the presence of decoherence. Our treatment is based on an invariant-embedding equation for the evolution of the coherent reflection amplitude coefficient in the length of a 1-dimensional disordered conductor, where decoherence is introduced at par with the disorder through an outcoupling, or stochastic absorption, of the wave amplitude into side (transverse) channels, and its subsequent incoherent re-injection into the conductor. This is essentially in the spirit of B{\"u}ttiker's reservoir-induced decoherence. The resulting evolution equation for the probability density of the 4-probe resistance in the presence of decoherence is then generalised from the 1-dimensional to the d-dimensional case following an anisotropic Migdal-Kadanoff-type procedure and analysed. The anisotropy, namely that the disorder evolves in one arbitrarily chosen direction only, is the main approximation here that makes the analytical treatment possible. A qualitatively new result is that arbitrarily small decoherence reduces the localisation-delocalisation transition to a crossover making resistance moments of all orders finite.Comment: 14 pages, 1 figure, revised version, to appear in Phys. Rev.

Modified Bethe-Weizsacker mass formula with isotonic shift and new driplines

Nuclear masses are calculated using the modified Bethe-Weizsacker mass formula in which the isotonic shifts have been incorporated. The results are compared with the improved liquid drop model with isotonic shift. Mass excesses predicted by this method compares well with the microscopic-macroscopic model while being much more simple. The neutron and proton drip lines have been predicted using this modified Bethe-Weizsacker mass formula with isotonic shifts.Comment: 9 pages including 2 figure

Alpha decay chains study for the recently observed superheavy element Z=117 within the Isospin Cluster Model

The recently observed $\alpha$-decay chains $^{293-294}117$ were produced by the fusion reactions with target $^{249}Bk$ and projectile $^{48}Ca$ at Dubna in Russia. The reported cross-sections for the mentioned reaction are $\sigma=0.5(+1.1,-0.4)$pb and $\sigma$=1.3(+1.5,-0.6)$pb$ at $E^{*}=35MeV$ and $E^{*}=39MeV$, respectively. The Q-values of $\alpha$-decay and the half-lives $Log_{10}T^{\alpha}_{1/2}$(s) are calculated for the $\alpha$-decay chains of $^{293-294}117$ nuclei, within the framework of Isospin Cluster Model (ICM). In the ICM model the proximity energy is improved by using the isospin dependent radius of parent, daughter and alpha particle. The binding energy $B(A_{i}, Z_{i})$ (i=1,2) of any nucleus of mass number A and atomic number Z was obtained from a phenomenological and more genaralized BW formula given by \cite{samanta02}. The calculated results in ICM are compared with the experimental results and other theoretical Macro-Microscopic(M-M), RMF(with NL3 and SFU Gold forces parameter) model calculations. The estimated values of $\alpha$-decay half-lives are in good agreement with the recent data. The ICM calculation is in favor of the persence of magic number at N=172

Seedless x seedless grape progeny: Technique, results and perspectives

Recent refinements in the in vitro embryo rescue technique employed to raise progenies from abortive ovules of seedless x seedless cultivars include addition of 0.2 ppm NAA (naphtaleneacetic acid) to the medium, inducing highly improved root systems and faster plant development. Selling seedless Vitis vinifera yielded seedless progeny only. Open pollinated Perlette and Flame Seedless gave rise to a high percentage (75 and 87%, respectively) of seedless progeny. Progeny from various crosses between seedless cultivars segregated into 65 normal seeded and 204 seedless. From the totality of 204 seedless progeny 192 bore fruit with very slight seed traces. Progeny from crosses between seeded and seedless segregated only 7.5-8% individuals with comparably slight seed traces, amounting to 1/3 of the progeny rated as seedless. Fresh weight determinations of aborted seeds per berry showed a pronouncedly lower weight in progenies from seedless x seedless crosses. Reduction in average berry size in the seedless fraction of seedless x seedless progenies compared to midparent values was of a similar order of magnitude as that obtained in seedless progeny derived from seeded x seedless crosses

Challenges for creating magnetic fields by cosmic defects

We analyse the possibility that topological defects can act as a source of magnetic fields through the Harrison mechanism in the radiation era. We give a detailed relativistic derivation of the Harrison mechanism at first order in cosmological perturbations, and show that it is only efficient for temperatures above T ~ 0.2 keV. Our main result is that the vector metric perturbations generated by the defects cannot induce vorticity in the matter fluids at linear order, thereby excluding the production of currents and magnetic fields. We show that anisotropic stress in the matter fluids is required to source vorticity and magnetic fields. Our analysis is relevant for any mechanism whereby vorticity is meant to be transferred purely by gravitational interactions, and thus would also apply to dark matter or neutrinos.Comment: 9 pages, 1 figure; minor corrections and additions; accepted for publication in Physical Review

Mathematical modelling of austempering by finite element method

Austempered ductile iron (ADI) possesses a superior toughness than ordinary cast iron because the residual phase associated with bainitic ferrite is retained aust-enite instead of martensite or carbide. The desired micro- structure (devoid of pearlite, martensite or carbide) can be obtained provided the effective cooling rates at diff-erent cross-sections are accurately determinable for components with varying shape, composition and heat treatment requirements. In this study, a finite element model (FEM) has been developed to predict the temperature profile along different cross-sections following austeni-tizing at 870°C and austempering at 370°C. Solid bodies of different shapes have been meshed into hexahedron ele-ments by the present software. The o verall global matrix equation has been numerically solved by the Gaussian elimination method. Finally, it is found that the results predicted by the present model is in well accordance with the relevant experimental data on austemperability