A Local Description of Dark Energy in Terms of Classical Two-Component Massive Spin-One Uncharged Fields on Spacetimes with Torsionful Affinities

It is assumed that the two-component spinor formalisms for curved spacetimes that are endowed with torsionful affine connexions can supply a local description of dark energy in terms of classical massive spin-one uncharged fields. The relevant wave functions are related to torsional affine potentials which bear invariance under the action of the generalized Weyl gauge group. Such potentials are thus taken to carry an observable character and emerge from contracted spin affinities whose patterns are chosen in a suitable way. New covariant calculational techniques are then developed towards deriving explicitly the wave equations that supposedly control the propagation in spacetime of the dark energy background. What immediately comes out of this derivation is a presumably natural display of interactions between the fields and both spin torsion and curvatures. The physical properties that may arise directly from the solutions to the wave equations are not brought out.Comment: About 10 pages, 47 reference

Colour Fields Computed in SU(3) Lattice QCD for the Static Tetraquark System

The colour fields created by the static tetraquark system are computed in quenched SU(3) lattice QCD, in a 24^3 x 48 lattice at beta=6.2 corresponding to a lattice spacing a=0.07261(85) fm. We find that the tetraquark colour fields are well described by a double-Y, or butterfly, shaped flux tube. The two flux tube junction points are compatible with Fermat points minimizing the total flux tube length. We also compare the diquark-diantiquark central flux tube profile in the tetraquark with the quark-antiquark fundamental flux tube profile in the meson, and they match, thus showing that the tetraquark flux tubes are composed of fundamental flux tubes.Comment: 5 pages, 7 figures, 0 tables, one reference added, work done partly under the PT-LQCD Collaboratio

Spin inversion devices with Fano anti-resonances

Analyzing spin transport of quasi-2D electrons gas moving through a semiconductor wave guide subject to a sectionally homogeneous tilted magnetic field, we found well-defined selection rules for resonant and antiresonant spin carrier transmission. Based on these selection rules and the band shift induced by the magnetic field strength and the tilting angles, we propose an efficient spin inversion device. For a polarized incoming electron beam, we can determine from our theoretical approach, physical conditions for spin-inversion efficiency up to 80%. We visualize this mechanism in terms of conductance and the spacial behavior of the wave function amplitude along the superlattice.Comment: 3 pages, 3 figures, regular pape

New gravitational solutions via a Riemann-Hilbert approach

We consider the Riemann-Hilbert factorization approach to solving the field equations of dimensionally reduced gravity theories. First we prove that functions belonging to a certain class possess a canonical factorization due to properties of the underlying spectral curve. Then we use this result, together with appropriate matricial decompositions, to study the canonical factorization of non-meromorphic monodromy matrices that describe deformations of seed monodromy matrices associated with known solutions. This results in new solutions, with unusual features, to the field equations.Comment: 29 pages, 2 figures; v2: reference added, matches published versio

On the gravitational stability of D1-D5-P black holes

We examine the stability of the nonextremal D1-D5-P black hole solutions. In particular, we look for the appearance of a superradiant instability for the spinning black holes but we find no evidence of such an instability. We compare this situation with that for the smooth soliton geometries, which were recently observed to suffer from an ergoregion instability, and consider the implications for the fuzzball proposal.Comment: 18 pages, 3 figures. Minor comments added to match published versio

Design sensitivity analysis of nonlinear structural response

A unified theory is described of design sensitivity analysis of linear and nonlinear structures for shape, nonshape and material selection problems. The concepts of reference volume and adjoint structure are used to develop the unified viewpoint. A general formula for design sensitivity analysis is derived. Simple analytical linear and nonlinear examples are used to interpret various terms of the formula and demonstrate its use

Regional Growth and Convergence: The Role of Human Capital in the Portuguese Regions

Potentially one of the most important determinants of regional economic growth and convergence is human capital, although due to a lack of data this factor is frequently omitted from econometric studies. In contrast, this paper constructs three measures of human capital at the NUTS III regional level for Portugal for the period 1991-2008 and then includes these variables in regional growth regressions. The results show that both secondary and higher levels of education have a significant positive effect on regional growth rates which may be regarded as supportive of Portuguese education policy, which over the last three decades has attempted to raise the regional human capital by locating higher education institutions across the country.Human capital, Regional convergence, GMM

Human Capital and Spatial Heterogeneity in the Iberian Countries’ Regional Growth and Convergence

Human capital is believed to be an important conditioning factor in explaining the convergence and the speed of convergence of regional economies, although it is usually excluded from the estimated models due to a lack of consistent data. In contrast this paper, using a newly constructed series on human capital at the NUTS III level for Portugal, evaluates the role of human capital on the speed of convergence using a spatial econometric methodology, for a sample of Iberian NUTS III regions over the period 1991-2006. This is the first study to consider human capital effects at the NUTS III level and the results show convergence, both absolute and conditional, occurs mainly in the peripheral group of regions, while human capital plays a positive role only in the club of the richest regions, in contrast with an insignificant effect in the periphery. There is also evidence of important regional spillovers between the regions and evidence of the importance of EU regional policy in enhancing the convergence of the NUTS III regions.Regional growth, beta-convergence, Human Capital, Spatial Effects