Single hole doped strongly correlated ladder with a static impurity

We consider a strongly correlated ladder with diagonal hopping and exchange interactions described by $t-J$ type hamiltonian. We study the dynamics of a single hole in this model in the presence of a static non-magnetic (or magnetic) impurity. In the case of a non-magnetic (NM) impurity we solve the problem analytically both in the triplet (S=1) and singlet (S=0) sectors. In the triplet sector the hole doesn't form any bound state with the impurity. However, in the singlet sector the hole forms bound states of different symmetries with increasing $J/t$ values. Binding energies of those impurity-hole bound states are compared with the binding energy of a pair of holes in absence of any impurity. In the case of magnetic impurity the analytical eigenvalue equations are solved for a large (50 X 2) lattice. In this case also, with increasing $J/t$ values, impurity-hole bound states of different symmetries are obtained. Binding of the hole with the impurity is favoured for the case of a ferromagnetic (FM) impurity than in the case of antiferromagnetic (AFM) impurity. However binding energy is found to be maximum for the NM impurity. Comparison of binding energies and various impurity-hole correlation functions indicates a pair breaking mechanism by NM impurity.Comment: 15 Pages, 6 figure

INFLUENCE OF ORGANIC MANURES AND GIBBERELLIC ACID ON GROWTH AND YIELD OF STRAWBERRY (Fragaria X ananassa DUCH.)

A field experiment was conducted to study the effect of organic manures and growth regulators on the growth and yield of two varieties of strawberry namely ‘Sweet Charlie’ and ‘Winter Dawn’. Six treatments were taken combining three organic manures viz. Vermicompost @ 3.0 t/ha, Mustard oil cake @ 1.0 t/ha and Neem cake @ 1.0 t/ha and two concentrations of gibberellic acid (GA3) viz. 75 ppm and 100 ppm along with a control. Foliar application of GA3 was carried out at 40 and 60 days after planting whereas organic manures were applied as basal dose. Results of the study suggested that higher doses i.e. 100 ppm of GA3 along with vermicompost exhibited more vegetative growth whereas 75 ppm GA3 resulted in higher fruit set and yield in both the varieties. It was found that vermicompost @ 3.0 t/ha combined with 100 ppm GA3 recorded the highest plant height (24.7 cm and 21.4 cm) and numbers of leaves per plant (46.0 and 68.7) in both Sweet Charlie and Winter Dawn varieties, respectively. Whereas, highest fruit diameter (3.3cm and 3.4cm), fruit length (4.6cm and 4.8cm), fruit weight (18.2 g and 17.9 g), number of fruits per plant (24.6 and 32.0), yield per plant (447.8 g and 572.1 g) and yield per hectare (18.80 t and 24.03 t) were recorded under vermicompost @ 3.0 t/ha in combination with 75 ppm GA3 in both Sweet Charlie and Winter Dawn varieties, respectively. It was observed that Winter Dawn variety produced a 28.0% higher yield as compared to Sweet Charlie under the best treatment i.e. vermicompost @ 3.0 t/ha in combination with 75 ppm GA3

The role of Turbulent Convection and wind in Geostrophic Circulation: Direct Numerical Simulation Study

Direct numerical simulations (DNS) are used over a three-dimensional rotating basin under geostrophic rotation, in order to understand the relative roles of buoyancy and wind stress on the heat and mass transport. Our main focus is on the large Rayleigh number regime (Ra, being the measure of buoyancy forcing) which is the order of 1012 to sustain turbulent convection. We also maintained small values of convective Rossby number Ro ~ 0.1 at a fixed Prandtl number, Pr ~ 5 while imposing a meridional wind stress pattern

On Approximating Total Variation Distance

Total variation distance (TV distance) is a fundamental notion of distance between probability distributions. In this work, we introduce and study the computational problem of determining the TV distance between two product distributions over the domain {0, 1}n. We establish the following results. 1. Exact computation of TV distance between two product distributions is #P-complete. This is in stark contrast with other distance measures such as KL, Chi-square, and Hellinger which tensorize over the marginals. 2. Given two product distributions P and Q with marginals of P being at least 1/2 and marginals of Q being at most the respective marginals of P, there exists a fully polynomial-time randomized approximation scheme (FPRAS) for computing the TV distance between P and Q. In particular, this leads to an efficient approximation scheme for the interesting case when P is an arbitrary product distribution and Q is the uniform distribution. We pose the question of characterizing the complexity of approximating the TV distance between two arbitrary product distributions as a basic open problem in computational statistics

Total Variation Distance Estimation Is as Easy as Probabilistic Inference

In this paper, we establish a novel connection between total variation (TV) distance estimation and probabilistic inference. In particular, we present an efficient, structure-preserving reduction from relative approximation of TV distance to probabilistic inference over directed graphical models. This reduction leads to a fully polynomial randomized approximation scheme (FPRAS) for estimating TV distances between distributions over any class of Bayes nets for which there is an efficient probabilistic inference algorithm. In particular, it leads to an FPRAS for estimating TV distances between distributions that are defined by Bayes nets of bounded treewidth. Prior to this work, such approximation schemes only existed for estimating TV distances between product distributions. Our approach employs a new notion of $partial$ couplings of high-dimensional distributions, which might be of independent interest.Comment: 24 page

Absorbing Phase Transition in a Four State Predator Prey Model in One Dimension

The model of competition between densities of two different species, called predator and prey, is studied on a one dimensional periodic lattice, where each site can be in one of the four states say, empty, or occupied by a single predator, or occupied by a single prey, or by both. Along with the pairwise death of predators and growth of preys, we introduce an interaction where the predators can eat one of the neighboring prey and reproduce a new predator there instantly. The model shows a non-equilibrium phase transition into a unusual absorbing state where predators are absent and the lattice is fully occupied by preys. The critical exponents of the system are found to be different from that of the Directed Percolation universality class and they are robust against addition of explicit diffusion.Comment: 10 pages, 6 figures, to appear in JSTA

Heat and mass transport in geostrophic horizontal convection with surface wind stress

Direct Numerical Simulations are conducted to investigate heat and mass transport of flow with buoyancy forcing and surface wind stress. We use a re-entrant channel model with thermal and mechanical forcing similar to the Southern Ocean, with increasing surface wind stress. The model fully characterises convection and turbulence in the fluid. The presence of convection appears to significantly enhance the buoyancydriven overturning, resulting in an overturning cell which dominates the flow field compared with a relatively shallow and weak wind-driven cell. The vertical heat transport also indicates that the majority of vertical advective heat transport occurs in the convective zone, with strong upwelling of heat in this region. These results indicate that the presence of convection significantly enhances the impact of buoyancy forcing in driving mass and heat transport.This research was supported by the Australian Research Council grant DP140103706

Raman spectra of unfilled and filled carbon nanotubes: Theory

The Raman spectra of two G-bands and a radial breathing mode (RBM) of unfilled and filled single-wall semiconducting and metallic carbon nanotubes have been investigated theoretically, in the presence of electron-phonon and phonon-phonon interactions. Excitation of low frequency optical plasmons in the metallic nanotube is responsible for the peak known as the Breit-Wigner-Fano (BWF) line shape in the G-band Raman spectra. In a filled nanotube there is an additional peak due to excitation of the phonon of the filling atom or molecule. Positions, shapes and relative strengths of these Raman peaks depend on the phonon frequencies of the nanotube and that of the filling atoms, and strengths and forms of the plasmon-phonon and phonon-phonon interactions. For example, filling atoms with phonon frequency close to the RBM frequency of the nanotube may broaden and lower the RBM Raman peak to such an extent that it may become barely visible. Hybridization between the G-bands and the filling atom phonon is also strong when these two frequencies are close to each other and it has important effects on the G-band and the BWF line shapes. When the phonon frequency of the filling atom is far from the RBM and G-band frequencies, it gives rise to a separate peak with modest effects on the RBM and G-band spectra. Raman spectra of semiconducting unfilled and filled nanotubes have similar behavior as those of metallic nanotubes except that normally they have Lorentzian line shapes and do not show a BWF line shape. However, if a semiconducting nanotube is filled with donor atoms, it is predicted that the BWF type line shape may be observed near the RBM, or the G-band or the filling atom Raman peak.Comment: To be published in Physical Review

Phase diagram of an exactly solvable t-J ladder model

We study a system of one-dimensional t-J models coupled to a ladder system. A special choice of the interaction between neighbouring rungs leads to an integrable model with supersymmetry, which is broken by the presence of rung interactions. We analyze the spectrum of low-lying excitations and ground state phase diagram at zero temperature.Comment: LaTeX, 8 pp. incl. 1 figur