Beyond conventional factorization: Non-Hermitian Hamiltonians with radial oscillator spectrum

The eigenvalue problem of the spherically symmetric oscillator Hamiltonian is revisited in the context of canonical raising and lowering operators. The Hamiltonian is then factorized in terms of two not mutually adjoint factorizing operators which, in turn, give rise to a non-Hermitian radial Hamiltonian. The set of eigenvalues of this new Hamiltonian is exactly the same as the energy spectrum of the radial oscillator and the new square-integrable eigenfunctions are complex Darboux-deformations of the associated Laguerre polynomials.Comment: 13 pages, 7 figure

Wronskian formula for confluent second-order supersymmetric quantum mechanics

The confluent second-order supersymmetric quantum mechanics, for which the factorization energies tend to a single value, is studied. We show that the Wronskian formula remains valid if generalized eigenfunctions are taken as seed solutions. The confluent algorithm is used to generate SUSY partners of the Coulomb potential.Comment: 7 pages, 1 figure, to be published in Physics Letters

Exactly Solvable Hydrogen-like Potentials and Factorization Method

A set of factorization energies is introduced, giving rise to a generalization of the Schr\"{o}dinger (or Infeld and Hull) factorization for the radial hydrogen-like Hamiltonian. An algebraic intertwining technique involving such factorization energies leads to derive $n$-parametric families of potentials in general almost-isospectral to the hydrogen-like radial Hamiltonians. The construction of SUSY partner Hamiltonians with ground state energies greater than the corresponding ground state energy of the initial Hamiltonian is also explicitly performed.Comment: LaTex file, 21 pages, 2 PostScript figures and some references added. To be published in J. Phys. A: Math. Gen. (1998

Quantum mechanical spectral engineering by scaling intertwining

Using the concept of spectral engineering we explore the possibilities of building potentials with prescribed spectra offered by a modified intertwining technique involving operators which are the product of a standard first-order intertwiner and a unitary scaling. In the same context we study the iterations of such transformations finding that the scaling intertwining provides a different and richer mechanism in designing quantum spectra with respect to that given by the standard intertwiningComment: 8 twocolumn pages, 5 figure

Temperature effects on sinking velocity of different Emiliania huxleyi strains

The sinking properties of three strains of Emiliania huxleyi in response to temperature changes were examined. We used a recently proposed approach to calculate sinking velocities from coccosphere architecture, which has the advantage to be applicable not only to culture samples, but also to field samples including fossil material. Our data show that temperature in the sub-optimal range impacts sinking velocity of E. huxleyi. This response is widespread among strains isolated in different locations and moreover comparatively predictable, as indicated by the similar slopes of the linear regressions. Sinking velocity was positively correlated to temperature as well as individual cell PIC/POC over the sub-optimum to optimum temperature range in all strains. In the context of climate change our data point to an important influence of global warming on sinking velocities. It has recently been shown that seawater acidification has no effect on sinking velocity of a Mediterranean E. huxleyi strain, while nutrient limitation seems to have a small negative effect on sinking velocity. Given that warming, acidification, and lowered nutrient availability will occur simultaneously under climate change scenarios, the question is what the net effect of different influential factors will be. For example, will the effects of warming and nutrient limitation cancel? This question cannot be answered conclusively but analyses of field samples in addition to laboratory culture studies will improve predictions because in field samples multi factor influences and even evolutionary changes are not excluded. As mentioned above, the approach of determining sinking rate followed here is applicable to field samples. Future studies could use it to analyse not only seasonal and geographic patterns but also changes in sinking velocity over geological time scales

Invariance properties for coefficients of symmetric functions

We show that several of the main structural constants for symmetric functions (Littlewood-Richardson coefficients, Kronecker coefficients, plethysm coefficients, and the Kostka-Foulkes polynomials) share invariance properties related to the operations of taking complements with respect to rectangles and adding rectangles.Nous montrons que plusieurs des principales constantes de structure de la theorie des fonctions symétriques (les coefficients de Littlewood-Richardson, les coefficients de Kronecker, les coefficients du plethysme, et les polynômes de Kostka-Foulkes) ont en commun des symetries décrites par des opérations de complémentation dans des rectangles et d’ajout de rectangles pour les partitions qui les etiquettent.Ministerio de Ciencia e InnovaciónMinisterio de Economía y CompetitividadJunta de AndalucíaFondo Europeo de Desarrollo RegionalNational Science Foundatio

Mamíferos encontrados ao Sul do Estado do Acre, Brasil.

Entre os anos de 2004 e 2008, sete inventários de mamíferos foram realizados em quatro áreas sob manejo florestal madeireiro e não madeireiro localizadas ao sul do Estado do Acre. A partir de transectos lineares instalados nas áreas, foi possível identificar 32 espécies pertencentes às ordens Artiodactyla, Perissodactyla, Carnivora, Primates, Rodentia e Xenarthra, que incluíram as espécies ameaçadas de extinção, de distribuição geográfica restrita ou pouco conhecidas. Entre os animais observados destaca-se a predominância dos primatas nas quatro áreas estudadas. Nesse caso, especula-se sobre a possibilidade desse grupo taxonômico ser utilizado como bioindicador da qualidade ambiental das áreas de manejo florestal no Estado do Acre.bitstream/item/77684/1/boletim-de-pesquisa-48.pd