Effect of Fibonacci Modulation On Superconductivity

We have studied finite-sized single band models with short range pairing interactions between electrons in presence of diagonal Fibonacci modulation in one dimension. Two models, namely the attractive Hubbard model and the Penson-Kolb model, have been investigated at half-filling at zero temperature by solving the Bogoliubov-de Gennes equations in real space within a mean field approximation. The competition between ``disorder'' and the pairing interaction leads to a suppression of superconductivity (of usual pairs with zero centre-of-mass momenta) in the strong-coupling limit while an enhancement of the pairing correlation is observed in the weak-coupling regime for both the models. However, the dissimilarity of the pairing mechanisms in these two models brings about notable difference in the results. The extent to which the bond ordered wave and the $\eta$-paired (of pairs with centre-of-mass momenta = $\pi$) phases of the Penson-Kolb model are affected by the disorder has also been studied in the present calculation. Some finite size effects are also identified.Comment: 14 pages, 13 figure

Agricultural growth linkages in Sub-Saharan Africa:

How much extra net income growth can be had in rural areas of Africa by increasing the spending power of local households? The answer depends on how rural households spend increments to income, whether the items desired can be imported to the local area in response to increased demand, and, if not, whether increased demand will lead to new local production or simply to price rises. For every dollar in new farm income earned, at least one additional dollar could be realized from growth multipliers, according to Agricultural Growth Linkages in Sub-Saharan Africa.Income Rural areas Africa., Agricultural development Africa., Agricultural policy Economic aspects., Households Zimbabwe., Social accounting., Africa sub-Saharan,

On the role of a new type of correlated disorder in extended electronic states in the Thue-Morse lattice

A new type of correlated disorder is shown to be responsible for the appearance of extended electronic states in one-dimensional aperiodic systems like the Thue-Morse lattice. Our analysis leads to an understanding of the underlying reason for the extended states in this system, for which only numerical evidence is available in the literature so far. The present work also sheds light on the restrictive conditions under which the extended states are supported by this lattice.Comment: 11 pages, LaTeX V2.09, 1 figure (available on request), to appear in Physical Review Letter

Extended States in a One-dimensional Generalized Dimer Model

The transmission coefficient for a one dimensional system is given in terms of Chebyshev polynomials using the tight-binding model. This result is applied to a system composed of two impurities located between $N$ sites of a host lattice. It is found that the system has extended states for several values of the energy. Analytical expressions are given for the impurity site energy in terms of the electron's energy. The number of resonant states grows like the number of host sites between the impurities. This property makes the system interesting since it is a simple task to design a configuration with resonant energy very close to the Fermi level $E_F$.Comment: 4 pages, 3 figure

Nuclei in Strongly Magnetised Neutron Star Crusts

We discuss the ground state properties of matter in outer and inner crusts of neutron stars under the influence of strong magnetic fields. In particular, we demonstrate the effects of Landau quantization of electrons on compositions of neutron star crusts. First we revisit the sequence of nuclei and the equation of state of the outer crust adopting the Baym, Pethick and Sutherland (BPS) model in the presence of strong magnetic fields and most recent versions of the theoretical and experimental nuclear mass tables. Next we deal with nuclei in the inner crust. Nuclei which are arranged in a lattice, are immersed in a nucleonic gas as well as a uniform background of electrons in the inner crust. The Wigner-Seitz approximation is adopted in this calculation and each lattice volume is replaced by a spherical cell. The coexistence of two phases of nuclear matter - liquid and gas, is considered in this case. We obtain the equilibrium nucleus corresponding to each baryon density by minimizing the free energy of the cell. We perform this calculation using Skyrme nucleon-nucleon interaction with different parameter sets. We find nuclei with larger mass and charge numbers in the inner crust in the presence of strong magnetic fields than those of the zero field case for all nucleon-nucleon interactions considered here. However, SLy4 interaction has dramatic effects on the proton fraction as well as masses and charges of nuclei. This may be attributed to the behaviour of symmetry energy with density in the sub-saturation density regime. Further we discuss the implications of our results to shear mode oscillations of magnetars.Comment: presented in "Exciting Physics Symposium" held in Makutsi, South Africa in November, 2011 and to be published in a book by Springer Verla

New Insights into Properties of Large-N Holographic Thermal QCD at Finite Gauge Coupling at (the Non-Conformal/Next-to) Leading Order in N

In the context of [1]'s string theoretic dual of large-N thermal QCD-like theories at finite gauge/string coupling (as part of the `MQGP' limit of [2]), we discuss the following. First, up to LO in N, using the results of [3], we show that the local T^3 of [2] is the T^2-invariant sLag of [3] in a resolved conifold. This, together with the results of [4], shows that for a (predominantly resolved or deformed) resolved warped deformed conifold, the local T^3 of [2] in the MQGP limit, is the T^2-invariant sLag of [3] justifying the construction of the delocalized SYZ type IIA mirror of the type IIB background of [1]. Then, using the prescription of [5], we obtain the temperature dependence of the thermal (and electrical) conductivity working up to leading order in N (the number of D3-branes), and upon comparison with [6] show that the results mimic a 1+1-dimensional Luttinger liquid with impurities. Further, including sub-leading non-conformal terms in the metric determined by M (the number of fractional D-branes = the number of colors = 3 in the IR after the end of a Seiberg duality cascade), by looking at respectively the scalar, vector and tensor modes of metric perturbations and using [7]'s prescription of constructing appropriate gauge-invariant perturbations, we obtain respectively the speed of sound, the diffusion constant and the shear viscosity \eta (and \eta/s) including the non-conformal O((g_s M^2) (g_s N_f)/N<<1)-corrections, N_f being the number of flavor D7-branes.Comment: 1+75 pages, LaTeX; Some corrections in Tc-related calculations, results unchange