An Analytical Description of Spin Effects in Hadron-Hadron Scattering via PMD-SQS Optimum Principle

In this paper an analytical description of spin-effects in hadron-hadron scattering is presented by using PMD-SQS-optimum principle in which the differential cross sections in the forward and backward c.m. angles are considered fixed from the experimental data. The experimental tests of the optimal predictions, obtained by using the available phase shifts, are discussed.Comment: 14 pages, 2 figure

Cold Attractive Spin Polarized Fermi Lattice Gases and the Doped Positive U Hubbard Model

Experiments on polarized fermion gases performed by trapping ultracold atoms in optical lattices, allow the study of an attractive Hubbard model for which the strength of the on site interaction is tuned by means of a Feshbach resonance. Using a well-known particle-hole transformation we discuss how results obtained for this system can be reinterpreted in the context of a doped repulsive Hubbard model. In particular we show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state of the two-dimensional doped positive U Hubbard model. We then use the results of numerical studies of the striped state to relate the periodicity of the FFLO state to the spin polarization. We also comment on the relationship of the $d_{x^2-y^2}$ superconducting phase of the doped 2D repulsive Hubbard model to a d-wave spin density wave state for the attractive case.Comment: 4 pages, 2 figure

Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites

Previous theoretical investigations of colossal magnetoresistance (CMR) materials explain this effect using a ``clustered'' state with preformed ferromagnetic islands that rapidly align their moments with increasing external magnetic fields. While qualitatively successful, explicit calculations indicate drastically different typical resistivity values in two- and three-dimensional lattices, contrary to experimental observations. This conceptual bottleneck in the phase-separated CMR scenario is resolved here considering the cooperative nature of the Mn-oxide lattice distortions. This induces power-law correlations in the quenched random fields used in toy models with phase competition. When these effects are incorporated, resistor-network calculations reveal very similar results in two and three dimensions, solving the puzzle.Comment: RevTeX 4, 4 figure

Interference Effects in the Conductance of Multi-Level Quantum Dots

Using exact-diagonalization techniques supplemented by a Dyson equation embedding procedure, the transport properties of multilevel quantum dots are investigated in the Kondo regime. The conductance can be decomposed into the contributions of each level. It is shown that these channels can carry a different phase, and destructive interference processes are observed when the phase difference between them is $\pm\pi$. This effect is very different from those observed in bulk metals with magnetic impurities, where the phase differences play no significant role. The effect is also different from other recent studies of interference processes in dots, as discussed in the text. In particular, no external magnetic field is here introduced, and the hopping amplitudes dot-leads for all levels are the same. However, conductance cancellations induced by interactions are still observed. Another interesting effect reported here is the formation of localized states that do not participate in the transport. When one of these states crosses the Fermi level, the electronic occupation of the quantum dot changes, modifying the many-body physics of the system and indirectly affecting the transport properties. Novel discontinuities between two finite conductance values can occur as the gate voltage is varied, as discussed here

CORE and the Haldane Conjecture

The Contractor Renormalization group formalism (CORE) is a real-space renormalization group method which is the Hamiltonian analogue of the Wilson exact renormalization group equations. In an earlier paper\cite{QGAF} I showed that the Contractor Renormalization group (CORE) method could be used to map a theory of free quarks, and quarks interacting with gluons, into a generalized frustrated Heisenberg antiferromagnet (HAF) and proposed using CORE methods to study these theories. Since generalizations of HAF's exhibit all sorts of subtle behavior which, from a continuum point of view, are related to topological properties of the theory, it is important to know that CORE can be used to extract this physics. In this paper I show that despite the folklore which asserts that all real-space renormalization group schemes are necessarily inaccurate, simple Contractor Renormalization group (CORE) computations can give highly accurate results even if one only keeps a small number of states per block and a few terms in the cluster expansion. In addition I argue that even very simple CORE computations give a much better qualitative understanding of the physics than naive renormalization group methods. In particular I show that the simplest CORE computation yields a first principles understanding of how the famous Haldane conjecture works for the case of the spin-1/2 and spin-1 HAF.Comment: 36 pages, 4 figures, 5 tables, latex; extensive additions to conten

Clonostachys chloroleuca: A novel pathogen causing cassava root rot disease in Misiones Province, Argentina

Cassava (Manihot esculenta) is a crucial food source facing a threat from Cassava Root Rot Disease (CRRD), often caused by fungi like Fusarium, Lasiodiplodia, Phytophthora, among others. In this study, roots from cassava plants displaying CRRD symptoms were collected in Argentina. The isolated fungus, identified as Clonostachys chloroleuca through morphological and molecular methods, was confirmed as the cause of CRRD. In vitro severity tests revealed a high severity value of 22%. The fungus exhibited vigorous growth on root surfaces, causing deep dark coloration and dry pulp consistency. In vivo assays on cassava plants supported the manifestation of typical CRRD symptoms. This study marks the first report of C. chloroleuca causing CRRD, emphasizing its potential threat to cassava production. Further research is essential to understand its pathogenic mechanisms and validate findings in real-world conditions.Fil: Madrassi, Lucas Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Departamento de Bioquímica Clinica; ArgentinaFil: Gonzalez, R. D.. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Departamento de Bioquímica Clinica; ArgentinaFil: Mónaco, C. I.. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Departamento de Bioquímica Clinica; ArgentinaFil: Zapata, Pedro Dario. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Departamento de Bioquímica Clinica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Alvarenga, Adriana Elizabet. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Departamento de Bioquímica Clinica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentin