Superforms in six-dimensional superspace

Indexación: Web of ScienceWe investigate the complex of differential forms in curved, six-dimensional, N = (1, 0) superspace. The superconformal group acts on this complex by super-Weyl transformations. An ambi-twistor-like representation of a second conformal group arises on a pure spinor subspace of the cotangent space. The p-forms are defined by super-Weylcovariant tensor fields on this pure spinor subspace. The on-shell dynamics of such fields is superconformal. We construct the superspace de Rham complex by successively obstructing the closure of forms. We then extend the analysis to composite forms obtained by wedging together forms of lower degree. Finally, we comment on applications to integration in curved superspace and propose a superspace formulation of the abelian limit of the non-abelian tensor hierarchy of N = (1, 0) superconformal models.http://link.springer.com/article/10.1007%2FJHEP05%282016%29016#aboutarticl

New Results in the CBF theory for medium-heavy nuclei

Momentum distributions, spectroscopic factors and quasi-hole wave functions of medium-heavy doubly closed shell nuclei have been calculated in the framework of the Correlated Basis Function theory, by using the Fermi hypernetted chain resummation techniques. The calculations have been done by using microscopic two-body nucleon-nucleon potentials of Argonne type, together with three-body interactions. Operator dependent correlations, up to the tensor channels, have been used.Comment: 6 pages, 3 figures, proceeding of the "XI Convegno su problemi di Fisica Nucleare Teorica" 11-14 Ottobre 2006, Cortona, Ital

Measuring aid flows : a new approach

Debate about the effectiveness of foreign aid has intensified in recent years, as budgetary pressures on aid have increased in donor countries. Whatever the merits of opposing arguments, the question is: do conventional measures of aid (such as OECD's Net ODA), which lump together grants and loans, accurately reflect true aid flows? The authors analyze the methodological shortcomings of conventional measures of aid and propose a new approach, which measures official aid flows as the sum of grants and the grant-equivalents of official loans (in a new aggregate they call"Effective Development Assistance,"or EDA). They show how results using this conceptually superior measure may differ significantly from conventional aggregates, providing a quite different view on major aid trends. They implement their approach empirically using data on some 40,000 official loans from the World Bank's DRS database--virtually all of the official loans to 133 developing countries from 1975 to 1995. The numerical results underscore several points: 1) The conventional approach has led to systematic overestimates of the concessionality of official loans. This overestimate has increased significantly since the mid-1980s. Conventional methods show a rising trend; the new method shows the opposite. 2) Net ODA increasingly overstates the true aid content of official flows, although the divergence between the two approaches is somewhat muted by the rising relative importance of grants over loans in total official flows.Strategic Debt Management,Economic Adjustment and Lending,Banks&Banking Reform,Payment Systems&Infrastructure,Economic Theory&Research,Economic Adjustment and Lending,Banks&Banking Reform,Strategic Debt Management,Economic Theory&Research,Payment Systems&Infrastructure

Ground state of medium-heavy doubly-closed shell nuclei in correlated basis function theory

The correlated basis function theory is applied to the study of medium-heavy doubly closed shell nuclei with different wave functions for protons and neutrons and in the jj coupling scheme. State dependent correlations including tensor correlations are used. Realistic two-body interactions of Argonne and Urbana type, together with three-body interactions have been used to calculate ground state energies and density distributions of the 12C, 16O, 40Ca, 48Ca and 208Pb nuclei.Comment: Latex 10 pages, 3 Tables, 10 Figure

Critical point symmetries in boson-fermion systems. The case of shape transition in odd nuclei in a multi-orbit model

We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model (E(5/12)) to describe odd nuclei at the critical point in the transition from the spherical to $\gamma$-unstable behaviour. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the three single particle orbitals j=1/2,3/2,5/2. Energy spectra and electromagnetic transitions at the critical point compare well with the results obtained within the Interacting Boson Fermion Model, with a boson-fermion Hamiltonian that describes the same physical situation.Comment: Phys. Rev. Lett. (in press

Coincidences of a shifted hexagonal lattice and the hexagonal packing

A geometric study of twin and grain boundaries in crystals and quasicrystals is achieved via coincidence site lattices (CSLs) and coincidence site modules (CSMs), respectively. Recently, coincidences of shifted lattices and multilattices (i.e. finite unions of shifted copies of a lattice) have been investigated. Here, we solve the coincidence problem for a shifted hexagonal lattice. This result allows us to analyze the coincidence isometries of the hexagonal packing by viewing the hexagonal packing as a multilattice.Comment: 8 pages, 2 figures, submitted to ICQ12 Conference Proceeding

Self-dual formulations of d=3 gravity theories in the path-integral framework

We study the connection, at the quantum level, between d=2+1 dimensional self-dual models with actions of growing (from first to fourth) order, governing the dynamics of helicity +2 (or -2) massive excitations. We obtain identities between generating functionals of the different models using the path-integral framework, this allowing to establish dual maps among relevant vacuum expectation values. We check consistency of these v.e.v.'s with the gauge invariance gained in each mapping.Comment: 26 pages. LaTeX. Minor changes. Published in Int. J Modern Phys. A; http://www.worldscinet.com/ijmp

Noise Folding in Compressed Sensing

The literature on compressed sensing has focused almost entirely on settings where the signal is noiseless and the measurements are contaminated by noise. In practice, however, the signal itself is often subject to random noise prior to measurement. We briefly study this setting and show that, for the vast majority of measurement schemes employed in compressed sensing, the two models are equivalent with the important difference that the signal-to-noise ratio is divided by a factor proportional to p/n, where p is the dimension of the signal and n is the number of observations. Since p/n is often large, this leads to noise folding which can have a severe impact on the SNR

Momentum distributions and spectroscopic factors of doubly-closed shell nuclei in correlated basis function theory

The momentum distributions, natural orbits, spectroscopic factors and quasi-hole wave functions of the C12, O16, Ca40, Ca48, and Pb208 doubly closed shell nuclei, have been calculated in the framework of the Correlated Basis Function theory, by using the Fermi hypernetted chain resummation techniques. The calculations have been done by using the realistic Argonne v8' nucleon-nucleon potential, together with the Urbana IX three-body interaction. Operator dependent correlations, which consider channels up to the tensor ones, have been used. We found noticeable effects produced by the correlations. For high momentum values, the momentum distributions show large enhancements with respect to the independent particle model results. Natural orbits occupation numbers are depleted by about the 10\% with respect to the independent particle model values. The effects of the correlations on the spectroscopic factors are larger on the more deeply bound states.Comment: Modified version of the previous paper (there are new figures). The paper has been accepted for publication in Physical Review