The Operator Spectrum of the Six-dimensional (1,0) Theory

We study the large N operator spectrum of the (1,0) superconformal chiral six-dimensional theory with E_8 global symmetry. This spectrum is dual to the Kaluza-Klein spectrum of supergravity on AdS_7 X S^4/Z_2 with a ten-dimensional E_8 theory at its singular locus. We identify those operators in short multiplets of OSp(6,2|2), whose dimensions are exact for any N. We also discuss more general issues concerning AdS/CFT duality on orbifold supergravity backgrounds.Comment: 16pp, Late

Decay of a Bound State under a Time-Periodic Perturbation: a Toy Case

We study the time evolution of a three dimensional quantum particle, initially in a bound state, under the action of a time-periodic zero range interaction with ``strength'' (\alpha(t)). Under very weak generic conditions on the Fourier coefficients of (\alpha(t)), we prove complete ionization as (t \to \infty). We prove also that, under the same conditions, all the states of the system are scattering states.Comment: LaTeX2e, 15 page

Ionization in damped time-harmonic fields

We study the asymptotic behavior of the wave function in a simple one dimensional model of ionization by pulses, in which the time-dependent potential is of the form $V(x,t)=-2\delta(x)(1-e^{-\lambda t} \cos\omega t)$, where $\delta$ is the Dirac distribution. We find the ionization probability in the limit $t\to\infty$ for all $\lambda$ and $\omega$. The long pulse limit is very singular, and, for $\omega=0$, the survival probability is $const \lambda^{1/3}$, much larger than $O(\lambda)$, the one in the abrupt transition counterpart, $V(x,t)=\delta(x)\mathbf{1}_{\{t\ge 1/\lambda\}}$ where $\mathbf{1}$ is the Heaviside function

Borel summability and Lindstedt series

Resonant motions of integrable systems subject to perturbations may continue to exist and to cover surfaces with parametric equations admitting a formal power expansion in the strength of the perturbation. Such series may be, sometimes, summed via suitable sum rules defining $C^\infty$ functions of the perturbation strength: here we find sufficient conditions for the Borel summability of their sums in the case of two-dimensional rotation vectors with Diophantine exponent $\tau=1$ (e. g. with ratio of the two independent frequencies equal to the golden mean).Comment: 17 pages, 1 figur

Nonlinear Schroedinger equation with two symmetric point interactions in one dimension

We consider a time-dependent one-dimensional nonlinear Schroedinger equation with a symmetric potential double well represented by two delta interactions. Among our results we give an explicit formula for the integral kernel of the unitary semigroup associated with the linear part of the Hamiltonian. Then we establish the corresponding Strichartz-type estimate and we prove local existence and uniqueness of the solution to the original nonlinear problem

DC magnetron discharge fluid model using a new numerical scheme

Numerical modelling of an electrical discharge by fluid model can be accomplished through different procedures and approaches. A 2D time-dependent one was applied in order to describe a cylindrical symmetry Argon DC planar magnetron discharge. All transport equations, which means continuity and momentum transfer equations for electrons and ions and electron mean energy transport equation are solved in the same manner, using corrected classical drift-diffusion expressions for fluxes. For the validity of this last approach, the presence of magnetic field has been introduced as a correction in the electronic flux expression, while for ions an effective electric field has been considered. Plasma potential is given by Poisson equation

2D fluid approaches of DC magnetron discharge

A two dimensional (r,z) time-dependent fluid model was developed and used to describe a DC planar magnetron discharge with cylindrical symmetry. The transport description of the charged species uses the corresponding first three moments of Boltzmann equation: continuity, momentum transfer and mean energy transfer (the latter one only for electrons), coupled with Poisson equation. An original way is proposed to treat the transport equations. Electron and ion momentum transport equations are reduced to the classical drift-diffusion expression of the fluxes since the presence of the magnetic field is introduced as an additional part in the electron flux, while for ions an effective electric field was considered. Thus, both continuity and mean energy transfer equations are solved in a classical manner. Numerical simulations were performed considering Argon as buffer gas, with a neutral pressure varying between 5 and 30 mtorr, a gas temperature from 300 to 350 K and cathode voltages lying from -200 up to -600 V. Results obtained for densities of the charged particle, fluxes and plasma potential are in good agreement with previous works.Laboratoire de Physique des Gaz el des Plasmas (LPGP).Consiliul National al Cercetarii Stiintifice din Invatamantul Superior (CNCSIS) - A/1344/40213/2003

Two-dimensional fluid approach to the dc magnetron discharge

A two-dimensional (r, z) time-dependent fluid model was developed and used to describe a dc planar magnetron discharge with cylindrical symmetry. The transport description of the charged species uses the corresponding first three moments of the Boltzmann equation: continuity, momentum transfer and mean energy transfer (the last one only for electrons), coupled with the Poisson equation. An original method is proposed to treat the transport equations. Electron and ion momentum transport equations are reduced to the classical drift-diffusion expression for the fluxes since the presence of the magnetic field is introduced as an additional part in the electron flux, while for ions an effective electric field was considered. Thus, both continuity and mean energy transfer equations are solved in a classical manner. Numerical simulations were performed considering argon as a buffer gas, with a neutral pressure varying between 5 and 30 mTorr, for different voltages applied on the cathode. Results obtained for densities of the charged particle, fluxes and plasma potential are in good agreement with those obtained in previous studies.C Costin would like to thank the French Government for his PhD fellowship at Laboratoire de Physique des Gaz et des Plasmas. We are also grateful to Dr T Minea for very helpful discussions. This work was partly supported by CNCSIS Romania, grant A/1344/2003

Collaborative procurement and private-sector housebuilding and refurbishment works: A pilot study investigation of the UK

Purpose Framed as a pilot study, the purpose of this paper is to study the perceived appropriateness of an existing collaborative procurement procedures (CPP) framework from the housebuilder’s perspective; seeking to improve its utility and stimulate further exploration. Design/methodology/approach Informed by an existing CPP framework, and conducted by a UK-based development professional, four in-depth semi-structured interviews were undertaken with senior housebuilding practitioners from London and surrounding counties. A qualitative analysis was then conducted for this sociological study. Findings Perceived appropriateness of the framework was high; however, a number of procedural improvements were identified, along with limitations. Future studies are recommended including the influence upon project performance of groundworker integration at the design stage. Research limitations/implications Limited to four interviews from one regional area, the study is an initial insight into the appropriateness of an existing CPP framework. Insights into why CP uptake is marginal within housebuilding were also gained. The research purpose was achieved but by offering a self-reflection upon practice (vis-à-vis wider generalisations) the findings provide a springboard for further studies. Practical implications The research identifies with current practice, industry perceptions, and paths towards improving the utility of the CPP framework. Social implications This study offers insights into the perceptions of private housebuilding practitioners of their own practices and the factors they find challenging within the social constructs of their industry. Originality/value This research constitutes one of the first studies in the UK to examine the CPP framework from the perspective of the private housebuilder and is undertaken with the express purpose of furthering that framework’s utility