Cyclic Lorentzian Lie Groups

We consider Lie groups equipped with a left-invariant cyclic Lorentzian metric. As in the Riemannian case, in terms of homogeneous structures, such metrics can be considered as different as possible from bi-invariant metrics. We show that several results concerning cyclic Riemannian metrics do not extend to their Lorentzian analogues, and obtain a full classification of three- and four-dimensional cyclic Lorentzian metrics

Electron correlations in a C20_{20} fullerene cluster: A lattice density-functional study of the Hubbard model

The ground-state properties of C$_{20}$ fullerene clusters are determined in the framework of the Hubbard model by using lattice density-functional theory (LDFT) and scaling approximations to the interaction-energy functional. Results are given for the ground-state energy, kinetic and Coulomb energies, local magnetic moments, and charge-excitation gap, as a function of the Coulomb repulsion $U/t$ and for electron or hole doping $\delta$ close half-band filling ($|\delta| \le 1$). The role of electron correlations is analyzed by comparing the LDFT results with fully unrestricted Hartree-Fock (UHF) calculations which take into account possible noncollinear arrangements of the local spin-polarizations. The consequences of the spin-density-wave symmetry breaking, often found in UHF, and the implications of this study for more complex fullerene structures are discussed.Comment: 18 pages, 7 figures, Submitted to PR

Damping-Antidamping Effect on Comets Motion

We make an observation about Galilean transformation on a 1-D mass variable systems which leads us to the right way to deal with mass variable systems. Then using this observation, we study two-bodies gravitational problem where the mass of one of the bodies varies and suffers a damping-antidamping effect due to star wind during its motion. For this system, a constant of motion, a Lagrangian and a Hamiltonian are given for the radial motion, and the period of the body is studied using the constant of motion of the system. Our theoretical results are applied to Halley's comet.Comment: 19 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:0910.468

Tests for the asymptotic behaviour of the gamma^* --> gamma pi^0 form factor

The gamma^* --> gamma pi^0 transition measured at different photon virtualities already provides us with a clean test for the behaviour of the pi^0 gamma^* gamma off-shell axial anomaly at large time-like squared momenta. It also allows reliable predictions for the branching ratio of heavy quarkonium decays into omega pi^0.Comment: Latex, 7 pages + 1 .ps figure, comments on the Brodsky-Lepage limit and 5 new references adde

Boron determination in steels by Inductively-Coupled Plasma spectometry (ICP)

The sample is treated with 5N H2SO4 followed by concentrated HNO3 and the diluted mixture is filtered. Soluble B is determined in the filtrate by Inductively-Coupled Plasma (ICP) spectrometry after addition HCl and extraction of Fe with ethyl-ether. The residue is fused with Na2CO3 and, after treatment with HCl, the insoluble B is determined by ICP spectrometry as before. The method permits determination of ppm amounts of B in steel

Radion Assisted Gauge Inflation

We propose an extension to the recently proposed extranatural or gauge inflation scenario in which the radius modulus field around which the Wilson loop is wrapped assists inflation as it shrinks. We discuss how this might lead to more generic initial conditions for inflation.Comment: 10 pages, 2 figure