Bose-Einstein Condensation in Anisotropic Harmonic Traps

We study the thermodynamic behaviour of an ideal gas of bosons trapped in a three-dimensional anisotropic harmonic oscillator potential. The condensate fraction as well as the specific heat is calculated using the Euler-Maclaurin approximation. For a finite number of particles there is no phase transition, but there is a well defined temperature at which the condensation starts. We also consider condensation in lower dimensions, and for one-dimensional systems we discuss the dependence of the condensate fraction and heat capacity on the ensemble used.Comment: LaTex, 17 pages, 7 ps-figure

Internal computational fluid mechanics on supercomputers for aerospace propulsion systems

The accurate calculation of three-dimensional internal flowfields for application towards aerospace propulsion systems requires computational resources available only on supercomputers. A survey is presented of three-dimensional calculations of hypersonic, transonic, and subsonic internal flowfields conducted at the Lewis Research Center. A steady state Parabolized Navier-Stokes (PNS) solution of flow in a Mach 5.0, mixed compression inlet, a Navier-Stokes solution of flow in the vicinity of a terminal shock, and a PNS solution of flow in a diffusing S-bend with vortex generators are presented and discussed. All of these calculations were performed on either the NAS Cray-2 or the Lewis Research Center Cray XMP

Longevity, Growth and Intergenerational Equity - The Deterministic Case

Challenges raised by ageing (increasing longevity) have prompted policy debates featuring policy proposals justified by reference to some notion of intergenerational equity. However, very different policies ranging from pre-savings to indexation of retirement ages have been justified in this way. We develop an overlapping generations model in continuous time which encompasses different generations with different mortality rates and thus longevity. Allowing for trend increases in both longevity and productivity, we address the issue of intergenerational equity under a utilitarian criterion when future generations are better off in terms of both material and non-material well being. Increases in productivity and longevity are shown to have very different implications for intergenerational distribution.

Organizing International Technological Collaboration in Subcontractor Relationships An Investigation of the Knowledge-Stickyness Problem

Technological knowledge is often claimed to be context-bound and sticking to local surroundings. This paper investigates how technological knowledge can be exchanged in international subcontractor relationships, using relationship-oriented organizational practices. Five hypotheses concerning such practices are tested. It is shown that the use of relationshiporiented practices varies with exports and the active development of subcontractors in product and process development activities. Moreover, international development-oriented subcontractors are more likely to use interpersonal exchange, electronic data interchange and formalized contracts than other types of subcontractors. Research implications as well as managerial implications are derived.Subcontracting, knowledge, international division og labour

Stopping power of antiprotons in H, H2, and He targets

The stopping power of antiprotons in atomic and molecular hydrogen as well as helium was calculated in an impact-energy range from 1 keV to 6.4 MeV. In the case of H2 and He the targets were described with a single-active electron model centered on the target. The collision process was treated with the close-coupling formulation of the impact-parameter method. An extensive comparison of the present results with theoretical and experimental literature data was performed in order to evaluate which of the partly disagreeing theoretical and experimental data are most reliable. Furthermore, the size of the corrections to the first-order stopping number, the average energy transferred to the target electrons, and the relative importance of the excitation and the ionization process for the energy loss of the projectile was determined. Finally, the stopping power of the H, H2, and He targets were directly compared revealing specific similarities and differences of the three targets.Comment: v1: 12 pages, 8 figures, and 1 table v2: 15 pages, 9 figures, and 2 tables; extended discussion on IPM in Method; influence of double ionization on stopping power discussed in Result

Pinning of stripes by local structural distortions in cuprate high-Tc superconductors

We study the spin-density wave (stripe) instability in lattices with mixed low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal symmetry. Within an explicit mean-field model it is shown how local LTT regions act as pinning centers for static stripe formation. We calculate the modulations in the local density of states near these local stripe regions and find that mainly the coherence peaks and the van Hove singularity (VHS) are spatially modulated. Lastly, we use the real-space approach to simulate recent tunneling data in the overdoped regime where the VHS has been detected by utilizing local normal state regions.Comment: Conference proceedings for Stripes1

The Price Responsiveness of Salmon Supply in the Short and Long Run

Productivity growth and competitiveness indicate that salmon supply is price responsive. However, in the short run supply is likely to be constrained by the biological production process, regulations, and capacity constraints. In this article, we estimate a restricted profit function for Norwegian salmon producers, which allows us to examine the industry’s short-run and long-run supply responsiveness separately. Using data spanning 1985 to 2004, we find that there is close to zero, own-price supply responsiveness in the short run. In the long run, this changes substantially as supply becomes elastic. This result can contribute to explaining the observed cyclical profitability in the salmon farming industry.Restricted profit function, supply, salmon farming, profit cycles, Demand and Price Analysis, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies, Research Methods/ Statistical Methods, D24, Q21, Q22,

Spin susceptibility of underdoped cuprates: the case of Ortho-II YBa_2Cu_3O_{6.5}

Recent inelastic neutron scattering measurements found that the spin susceptibility of detwinned and highly ordered ortho-II YBa_2Cu_3O_{6.5} exhibits, in both the normal and superconducting states, one-dimensional incommensurate modulations at low energies which were interpreted as a signature of dynamic stripes. We propose an alternative model based on quasiparticle transitions between the arcs of a truncated Fermi surface. Such transitions are resonantly enhanced by scattering to the triplet spin resonance. We show that the anisotropy in the experimental spin response is consistent with this model if the gap at the saddle points is anisotropic.Comment: 5 fives, 3 postscript figure