On Pair-Particle Distribution in Imperfect Bose Gas

A simple model of estimating the radial distribution function of an imperfect Bose gas in the ground state is presented. The model is based on integro-differential equations derived by considering the space boson distribution in an external field. With the approach proposed, the particular case of dilute Bose gas is investigated within the hard sphere approximation and beyond.Comment: 8 pages, LaTEX, no Figures. Submitted to Phys. Lett.

Curvaton and the inhomogeneous end of inflation

We study the primordial density perturbations and non-Gaussianities generated from the combined effects of an inhomogeneous end of inflation and curvaton decay in hybrid inflation. This dual role is played by a single isocurvature field which is massless during inflation but acquire a mass at the end of inflation via the waterfall phase transition. We calculate the resulting primordial non-Gaussianity characterized by the non-linearity parameter, $f_{NL}$, recovering the usual end-of-inflation result when the field decays promptly and the usual curvaton result if the field decays sufficiently late.Comment: 13 pages, 5 figure

Modelling cell wall growth using a fibre-reinforced hyperelastic–viscoplastic constitutive law

AbstractA fibre-reinforced hyperelastic–viscoplastic model using a finite strain Finite Element (FE) analysis is presented to study the expansive growth of cell walls. Based on the connections between biological concepts and plasticity theory, e.g. wall-loosening and plastic yield, wall-stiffening and plastic hardening, the modelling of cell wall growth is established within a framework of anisotropic viscoplasticity aiming to represent the corresponding biology-controlled behaviour of a cell wall. In order to model in vivo growth, special attention is paid to the differences between a living cell and an isolated wall. The proposed hyperelastic–viscoplastic theory provides a unique framework to clarify the interplay between cellulose microfibrils and cell wall matrix and how this interplay regulates sustainable growth in a particular direction while maintaining the mechanical strength of the cell walls by new material deposition. Moreover, the effect of temperature is taken into account. A numerical scheme is suggested and FE case studies are presented and compared with experimental data

Dynamics of a Disoriented Chiral Condensate

We use the linear $\sigma$ model to analyse the dynamics of a disoriented chiral condensate. For idealized boundary conditions appropriate to high energy collisions, the problem can be reduced to a one dimensional one. The evolution of the chiral state is then that of a simple dynamical system and can be studied analytically.Comment: 14 pages Latex, LPTHE Orsay 94/18 , SPhT T94/01

Carrier relaxation in Si/SiO2_2 quantum dots

Carrier relaxation due to both optical and nonradiative intraband transitions in silicon quantum dots in SiO$_2$ has been considered. Interaction of confined holes with optical phonons has been studied. The Huang-Rhys factor is calculated for such transitions. The probability of intraband transition of a confined hole emitting several optical phonons is estimated.Comment: 8 pages, 2 figures, submitted as an extended abstract to the E-MRS Spring Meeting 200

Effect of Background Evolution on the Curvaton Non-Gaussianity

We investigate how the background evolution affects the curvature perturbations generated by the curvaton, assuming a curvaton potential that may deviate slightly from the quadratic one, and parameterizing the background fluid density as \rho\propto a^{-\alpha}, where a is the scale factor, and \alpha depends on the background fluid. It turns out that the more there is deviation from the quadratic case, the more pronounced is the dependence of the curvature perturbation on \alpha. We also show that the background can have a significant effect on the nonlinearity parameters f_NL and g_NL. As an example, if at the onset of the curvaton oscillation there is a dimension 6 contribution to the potential at 5 % level and the energy fraction of the curvaton to the total one at the time of its decay is at 1 %, we find variations \Delta f_NL \sim \mathcal{O}(10) and \Delta g_NL \sim \mathcal{O}(10^4) between matter and radiation dominated backgrounds. Moreover, we demonstrate that there is a relation between f_NL and g_NL that can be used to probe the form of the curvaton potential and the equation of state of the background fluid.Comment: 14 pages, 8 figure

Metal Abundance Calibration of the Ca II Triplet Lines in RR Lyrae Stars

The GAIA satellite is likely to observe thousands of RR Lyrae stars within a small spectral window, between 8470A and 8750A, at a resolution of 11,500. In order to derive the metallicity of RR Lyrae stars from Gaia, we have obtained numerous spectra of RR Lyrae stars at a resolution of 35,000 with the Apache Point Observatory 3.5 m echelle spectrograph. We have correlated the Ca II triplet line strengths with metallicity as derived from Fe II abundances, analogous to Preston's (1959) use of the Ca II K line to estimate the metallicity of RR Lyrae stars. The Ca II line at 8498A is the least blended with neighboring Paschen lines and thus provides the best correlation.Comment: Accepted for publication in Astrophysics & Space Scienc

Development of a novel 3D simulation modelling system for distributed manufacturing

This paper describes a novel 3D simulation modelling system for supporting our distributed machine design and control paradigm with respect to simulating and emulating machine behaviour on the Internet. The system has been designed and implemented using Java2D and Java3D. An easy assembly concept of drag-and-drop assembly has been realised and implemented by the introduction of new connection features (unified interface assembly features) between two assembly components (modules). The system comprises a hierarchical geometric modeller, a behavioural editor, and two assemblers. During modelling, designers can combine basic modelling primitives with general extrusions and integrate CAD geometric models into simulation models. Each simulation component (module) model can be visualised and animated in VRML browsers. It is reusable. This makes machine design re-configurable and flexible. A case study example is given to support our conclusions

Gravitational Wave Background and Non-Gaussianity as a Probe of the Curvaton Scenario

We study observational implications of the stochastic gravitational wave background and a non-Gaussian feature of scalar perturbations on the curvaton mechanism of the generation of density/curvature fluctuations, and show that they can determine the properties of the curvaton in a complementary manner to each other. Therefore even if Planck could not detect any non-Gaussianity, future space-based laser interferometers such as DECIGO or BBO could practically exhaust its parameter space.Comment: 16 pages, 2 figure

Signals of Disoriented Chiral Condensate

If a disoriented chiral condensate is created over an extended space-time region following a rapid cooling in hadronic or nuclear collisions, the misalignment of the condensate with the electroweak symmetry breaking can generate observable effects in the processes which involve both strong and electromagnetic interactions. We point out the relevance of the dilepton decay of light vector mesons as a signal for formation of the disoriented condensate. We predict that the decay \rho^0 to dileptons will be suppressed and/or the \rho resonance peak widens, while the decay \omega to dileptons will not be affected by the condensate.Comment: 13 pages in LaTeX, UCB-PTH-94/05, LBL-3533