Phase Fluctuations in Strongly Coupled dd-Wave Superconductors

We present a numerically exact solution for the BCS Hamiltonian at any temperature, including the degrees of freedom associated with classical phase, as well as amplitude, fluctuations via a Monte Carlo (MC) integration. This allows for an investigation over the whole range of couplings: from weak attraction, as in the well-known BCS limit, to the mainly unexplored strong-coupling regime of pronounced phase fluctuations. In the latter, for the first time two characteristic temperatures $T^\star$ and $T_c$, associated with short- and long-range ordering, respectively, can easily be identified in a mean-field-motivated Hamiltonian. $T^\star$ at the same time corresponds to the opening of a gap in the excitation spectrum. Besides introducing a novel procedure to study strongly coupled d-wave superconductors, our results indicate that classical phase fluctuations are not sufficient to explain the pseudo-gap features of high-temperature superconductors (HTS).Comment: 5 pages, 3 figure

Characterization and comparative evaluation of novel planar electromagnetic sensors

The characterization of three types of novel planar electromagnetic sensors: 1) meander; 2) mesh; and 3) interdigital configuration, has been studied and their comparative performance has been evaluated based on their areas of applications. All of them are suitable for inspection and evaluation of system properties without destroying them. The experiments on fabricated sensors have been conducted and the results are presented here. The target application is to use a mixture of different types of sensors to detect plasti

A low-cost sensing system for quality monitoring of dairy products

The dairy industry is in need of a cost-effective, highly reliable, very accurate, and fast measurement system to monitor the quality of dairy products. This paper describes the design and fabrication works undertaken to develop such a system. The techniques used center around planar electromagnetic sensors operating with radio frequency excitation. Computer-aided computation, being fast, facilitates on-line monitoring of the quality. The sensor technology proposed has the ability to perform volumetric penetrative measurements to measure properties throughout the bulk of the product

Supernovae constraints on dark energy and modified gravity models

We use the Type Ia Supernova gold sample to constrain the parameters of dark energy models namely the Cardassian, Dvali-Turner (DT) and generalized Chaplygin gas (GCG) models. In our best fit analysis for these dark energy proposals we consider flat and the non-flat priors. For all models, we find that relaxing the flatness condition implies that data favors a positive curvature; moreover, the GCG model is nearly flat, as required by Cosmic Microwave Background (CMB) observations.Comment: 6 pages, Latex file + 9 eps figures + (jpconf.cls,jpconf11.clo), to appear in the Proceedings of the Fourth Meeting on Constrained Dynamics and Quantum Gravity (QG05), Cala Gonone (Italy) September 12-16 200

Fabrication of a repulsive-type magnetic bearing using a novel arrangement of permanent magnets for vertical-rotor suspension

A repulsive-type magnetic bearing system has been fabricated in which the rotor of a vertical-shaft-type motor is levitated due to the repulsive force between two sets of permanent magnets. A novel arrangement of permanent magnets has been reported here, which has made the suspension of the rotor possible. The system is planned to be applied for pumping milks and other related products in the New Zealand dairy industry

Structural studies of phosphorus induced dimers on Si(001)

Renewed focus on the P-Si system due to its potential application in quantum computing and self-directed growth of molecular wires, has led us to study structural changes induced by P upon placement on Si(001)-$p(2\times 1)$. Using first-principles density functional theory (DFT) based pseudopotential method, we have performed calculations for P-Si(001) system, starting from an isolated P atom on the surface, and systematically increasing the coverage up to a full monolayer. An isolated P atom can favorably be placed on an {\bf M} site between two atoms of adjacent Si dimers belonging to the same Si dimer row. But being incorporated in the surface is even more energetically beneficial due to the participation of the {\bf M} site as a receptor for the ejected Si. Our calculations show that up to 1/8 monolayer coverage, hetero-dimer structure resulting from replacement of surface Si atoms with P is energetically favorable. Recently observed zig-zag features in STM are found to be consistent with this replacement process. As coverage increases, the hetero-dimers give way to P-P ortho-dimers on the Si dimer rows. This behavior is similar to that of Si-Si d-dimers but are to be contrasted with the Al-Al dimers, which are found between adjacent Si dimers rows and in a para-dimer arrangement. Unlike Al-Si system P-Si does not show any para to ortho transition. For both systems, the surface reconstruction is lifted at about one monolayer coverage. These calculations help us in understanding the experimental data obtained using scanning tunneling microscope.Comment: To appear in PR

Evolution of Tachyon Kink with Electric Field

We investigate the decay of an inhomogeneous D1-brane wrapped on a $S^1$ with an electric field. The model that we consider consists of an array of tachyon kink and anti-kink with a constant electric flux. Beginning with an initially static configuration, we numerically evolve the tachyon field with some perturbations under a fixed boundary condition at diametrically opposite points on the circle $S^1$. When the electric flux is smaller than the critical value, the tachyon kink becomes unstable; the tachyon field rolls down the potential, and the lower dimensional D0- and $\bar {\rm D}0$-brane become thin, which resembles the caustic formation known for this type of the system in the literature. For the supercritical values of the electric flux, the tachyon kink remains stable.Comment: 27 pages, 8 figures, some changes, one reference added, version to appear in JHE

Interacting holographic tachyon model of dark energy

We propose a holographic tachyon model of dark energy with interaction between the components of the dark sector. The correspondence between the tachyon field and the holographic dark energy densities allows the reconstruction of the potential and the dynamics of the tachyon scalar field in a flat Friedmann-Robertson-Walker universe. We show that this model can describe the observed accelerated expansion of our universe with a parameter space given by the most recent observational results.Comment: 7 pages, 8 figures, accepted for publication in IJMP

Dirichlet Boundary State in Linear Dilaton Background

Dirichlet-branes have emerged as important objects in studying nonperturbative string theory. It is important to generalize these objects to more general backgrounds other than the usual flat background. The simplest case is the linear dilaton condensate. The usual Dirichlet boundary condition violates conformal invariance in such a background. We show that by switching on a certain boundary interaction, conformal invariance is restored. An immediate application of this result is to two dimensional string theory.Comment: 6 pages, harvmac, some remarks are modified and one reference is added, formulas remain the sam