Search results for "Tensor"
showing 10 items of 550 documents
An intrinsic characterization of spherically symmetric spacetimes
2010
We give the necessary and sufficient (local) conditions for a metric tensor to be a non conformally flat spherically symmetric solution. These conditions exclusively involve explicit concomitants of the Riemann tensor. As a direct application we obtain the {\em ideal} labeling of the Schwarzschild, Reissner-Nordstr\"om and Lema\^itre-Tolman-Bondi solutions.
Type D vacuum solutions: a new intrinsic approach
2013
We present a new approach to the intrinsic properties of the type D vacuum solutions based on the invariant symmetries that these spacetimes admit. By using tensorial formalism and without explicitly integrating the field equations, we offer a new proof that the upper bound of covariant derivatives of the Riemann tensor required for a Cartan-Karlhede classification is two. Moreover we show that, except for the Ehlers-Kundt's C-metrics, the Riemann derivatives depend on the first order ones, and for the C-metrics they depend on the first order derivatives and on a second order constant invariant. In our analysis the existence of an invariant complex Killing vector plays a central role. It al…
An intrinsic characterization of the Kerr metric
2009
We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve explicit concomitants of the Riemann tensor.
Photo-production of tensor mesons
2016
Assuming that the f 2 (1270), f ′2 (1525), a 2 (1320), and K * 2 (1430) resonances are dynamically generated states from the vector meson-vector meson interactions in L = 0 and spin 2, we study the γp → f 2 (1270)[f ′2 (1525)]p , γp → a 0 2 (1320)p , and γp → K * 2 (1430)Λ(Σ) reactions. For the γp → f 2 (1270)p reaction, we find that the theoretical results for the differential cross sections are in good agreement with the experimental measurements and provide support for the molecular picture of the f 2 (1270) in the first baryonic reaction where it has been tested. Furthermore, we predict also the total and differential cross sections for other reactions. The results can be tested in futu…
The methods of XLOOPS An introduction to parallel space techniques
1997
Abstract The package XLOOPS presented in this workshop relies on the application of parallel space techniques. We introduce these techniques covering the following topics: • - The generation of integral representations for massive two-loop diagrams. • - The treatment of tensor structures. • - The handling of the γ-algebra in this scheme. • - The separation of UV and IR divergences in analytic expressions. We present two-loop examples taken from Standard Model calculations.
Measurement of K-e3(0) form factors
2004
The semi-leptonic decay of the neutral K meson $K^{0}_{L} \to \pi^{\pm}e^{\mp}\nu (K_{e3})$, was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector $(f_{+}(q^{2}))$, scalar $(f_{S})$ and tensor $(f_{T})$ interactions were measured. The linear slope of the vector form factor $\lambda_{+} = 0.0284 \pm 0.0007 \pm 0.0013$ and values for the ratios $|f_{S}/f_{+}(0)|=0.015^{+0.007}_{-0.010} \pm 0.012$ and $|f_{T}/f_{+}(0)|=0.05^{+0.03}_{-0.04} \pm 0.03$ were obtained. The values fo…
The use of maximum entropy statistics combined with simulation methods to determine the structure of 4-dimethylamino-3-cyanobiphenyl
1997
Abstract 4-dimethylamino-3-cyanobiphenyl (4-DMA-3-CB) was characterised with respect to non-linear optical (NLO) properties in the gas phase and in the crystal. The crystal structure was solved from a series of electron diffraction patterns using both molecular modelling and ab initio maximum entropy techniques combined with log-likelihood evaluation. The agreement between the two methods is excellent and the structure evaluation permits an analysis of the major components of the hyperpolarisability tensor in the crystal framework.
Dielectric versus topographic contrast in near-field microscopy
1996
Using a fully vectorial three-dimensional numerical approach (generalized field propagator, based on Green's tensor technique), we investigate the near-field images produced by subwavelength objects buried in a dielectric surface. We study the influence of the object index, size, and depth on the near field. We emphasize the similarity between the near field spawned by an object buried in the surface (dielectric contrast) and that spawned by a protrusion on the surface (topographic contrast). We show that a buried object with a negative dielectric contrast (i.e., with a smaller index than its surrounding medium) produces a near-field image that is reversed from that of an object with a posi…
Calculation of local pressure tensors in systems with many-body interactions
2005
Local pressures are important in the calculation of interface tensions and in analyzing micromechanical behavior. The calculation of local pressures in computer simulations has been limited to systems with pairwise interactions between the particles, which is not sufficient for chemically detailed systems with many-body potentials such as angles and torsions. We introduce a method to calculate local pressures in systems with n-body interactions (n=2,3,4,) based on a micromechanical definition of the pressure tensor. The local pressure consists of a kinetic contribution from the linear momentum of the particles and an internal contribution from dissected many-body interactions by infinitesim…
Evolution of collectivity in the78Ni region: Coulomb excitation of74Ni at intermediate energies.
2014
The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neu…