On d=4d=4 Yang-Mills instantons in a spherically symmetric background

We present arguments for the existence of self-dual Yang-Mills instantons for several spherically symmetric backgrounds with Euclidean signature. The time-independent Yang-Mills field has finite action and a vanishing energy momentum tensor and does not disturb the geometry. We conjecture the existence of similar solutions for any nonextremal SO(3)-spherically symmetric background.Comment: 6 pages, 3 figures; v2: references adde

Einstein-Yang-Mills-Chern-Simons solutions in D=2n+1 dimensions

We investigate finite energy solutions of the Einstein--Yang-Mills--Chern-Simons system in odd spacetime dimensions, D=2n+1, with n>1. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. In contrast with the Abelian case, the contribution of the Chern-Simons term is nontrivial already in the static, spherically symmetric limit. Both globally regular, particle-like solutions and black holes are constructed numerically for several values of D. These solutions carry a nonzero electric charge and have finite mass. For globally regular solutions, the value of the electric charge is fixed by the Chern-Simons coupling constant. The black holes can be thought as non-linear superpositions of Reissner-Nordstrom and non-Abelian configurations. A systematic discussion of the solutions is given for D=5, in which case the Reissner-Nordstrom black hole becomes unstable and develops non-Abelian hair. We show that some of these non-Abelian configurations are stable under linear, spherically symmetric perturbations. A detailed discussion of an exact D=5 solution describing extremal black holes and solitons is also provided.Comment: 34 pages, 14 figures; v2: misprints corrected and references adde

Quantum States of Neutrons in Magnetic Thin Films

We have studied experimentally and theoretically the interaction of polarized neutrons with magnetic thin films and magnetic multilayers. In particular, we have analyzed the behavior of the critical edges for total external reflection in both cases. For a single film we have observed experimentally and theoretically a simple behavior: the critical edges remain fixed and the intensity varies according to the angle between the polarization axis and the magnetization vector inside the film. For the multilayer case we find that the critical edges for spin up and spin down polarized neutrons move towards each other as a function of the angle between the magnetization vectors in adjacent ferromagnetic films. Although the results for multilayers and single thick layers appear to be different, in fact the same spinor method explains both results. An interpretation of the critical edges behavior for the multilyers as a superposition of ferromagnetic and antifferomagnetic states is given.Comment: 6 pages, 5 figure

Chlorophylls - natural solar cells

A molecular modeling study was conducted on a series of six natural occurring chlorophylls. Quantum chemistry calculated orbital energies were used to estimate frequency of transitions between occupied molecular orbital and unoccupied molecular orbital energy levels of chlorophyll molecules in vivo conditions in standard (ASTMG173) environmental conditions. Obtained results are in good agreement with energies necessary to fix the Magnesium atom by chlorophyll molecules and with occurrence of chlorophylls in living vegetal organisms.Comment: 6 pages, 1 figure, 4 tables; paper in proceeding

On the continuity of spectra for families of magnetic pseudodifferential operators

For families of magnetic pseudodifferential operators defined by symbols and magnetic fields depending continuously on a real parameter $\epsilon$, we show that the corresponding family of spectra also varies continuously with $\epsilon$.Comment: 22 page

Instantonic dyons of Yang-Mills--Chern-Simons models in d=2n+1 dimensions, n>2

We investigate finite energy solutions of Yang-Mills--Chern-Simons systems in odd spacetime dimensions, d=2n+1, with n>2. This can be carried out systematically for all n, but the cases n=3,4 corresponding to a 7,8 dimensional spacetime are treated concretely. These are static and spherically symmetric configurations, defined in a flat Minkowski background. The value of the electric charge is fixed by the Chern-Simons coupling constant.Comment: 15 pages, 4 figure

Skyrmions around Kerr black holes and spinning BHs with Skyrme hair

We study solutions of the Einstein-Skyrme model. Firstly we consider test field Skyrmions on the Kerr background. These configurations -- hereafter dubbed Skerrmions -- can be in equilibrium with a Kerr black hole (BH) by virtue of a synchronisation condition. We consider two sectors for Skerrmions. In the sector with non-zero baryon charge, Skerrmions are akin to the known Skyrme solutions on the Schwarzschild background. These `topological' configurations reduce to flat spacetime Skyrmions in a vanishing BH mass limit; moreoever, they never become "small" perturbations on the Kerr background: the non-linearities of the Skyrme model are crucial for all such Skerrmions. In the non-topological sector, on the other hand, Skerrmions have no analogue on the Schwarzschild background. Non-topological Skerrmions carry not baryon charge and bifurcate from a subset of Kerr solutions defining an existence line. Therein the appropriate truncation of the Skyrme model yield a linear scalar field theory containing a complex plus a real field, both massive and decoupled, and the Skerrmions reduce to the known stationary scalar clouds around Kerr BHs. Moreover, non-topological Skerrmions trivialise in the vanishing BH mass limit. We then discuss the backreaction of these Skerrmions, that yield rotating BHs with synchronised Skyrme hair, which continously connect to the Kerr solution (self-gravitating Skyrmions) in the non-topological (topological) sector. In particular, the non-topological hairy BHs provide a non-linear realisation, within the Skyrme model, of the synchronous stationary scalar clouds around Kerr.Comment: 23 pages, 7 figures; to appear in JHE

Results of Evolution Supervised by Genetic Algorithms

A series of results of evolution supervised by genetic algorithms with interest to agricultural and horticultural fields are reviewed. New obtained original results from the use of genetic algorithms on structure-activity relationships are reported.Comment: 6 pages, 1 Table, 2 figure