Spectral microscopic mechanisms and quantum phase transitions in a 1D correlated problem

In this paper we study the dominant microscopic processes that generate nearly the whole one-electron removal and addition spectral weight of the one-dimensional Hubbard model for all values of the on-site repulsion $U$. We find that for the doped Mott-Hubbard insulator there is a competition between the microscopic processes that generate the one-electron upper-Hubbard band spectral-weight distributions of the Mott-Hubbard insulating phase and finite-doping-concentration metallic phase, respectively. The spectral-weight distributions generated by the non-perturbative processes studied here are shown elsewhere to agree quantitatively for the whole momentum and energy bandwidth with the peak dispersions observed by angle-resolved photoelectron spectroscopy in quasi-one-dimensional compounds.Comment: 18 pages, 2 figure

Superconductivity Driven by Chain Coupling and Electronic Correlations

We present an analysis of a system of weakly coupled Hubbard chains based on combining an exact study of spectral functions of the uncoupled chain system with a renormalization group method for the coupled chains. For low values of the onsite repulsion $U$ and of the doping $\delta$, the leading instability is towards a superconducting state. The process includes excited states above a small correlation pseudogap. Similar features appear in extended Hubbard models in the vicinity of commensurate fillings. Our theoretical predictions are consistent with the phase diagram observed in the (TMTTF)$_2$X and (TMTSF)$_2$X series of organic compounds.Comment: 7 pages, 2 figure

One-Particle Spectral Properties of Mott-Hubbard Insulators

We use an exact holon and spinon Landau-liquid functional which describes the holon - spinon interactions at all scattering orders, to study correlation functions of integrable multicomponent many-particle problems showing both linear and non-linear energy bands. We consider specific cases when the dominant non-linear band terms are quadratic and apply our results to the evaluation of the 1D Hubbard model correlation functions beyond conformal-field theory.Comment: 10 Pages, Revte

One-Electron Singular Branch Lines of the Hubbard Chain

The momentum and energy dependence of the weight distribution in the vicinity of the one-electron spectral-function singular branch lines of the 1D Hubbard model is studied for all values of the electronic density and on-site repulsion $U$. To achieve this goal we use the recently introduced pseudofermion dynamical theory. Our predictions agree quantitatively for the whole momentum and energy bandwidth with the peak dispersions observed by angle-resolved photoelectron spectroscopy in the quasi-1D organic conductor TTF-TCNQ.Comment: Replaced with shortened version; 4 figure

Complete Pseudohole and Heavy-Pseudoparticle Operator Representation for the Hubbard Chain

We introduce the pseudohole and heavy-pseudoparticle operator algebra that generates all Hubbard-chain eigenstates from a single reference vacuum. In addition to the pseudoholes already introduced for the description of the low-energy physics, this involves the heavy pseudoparticles associated with Hamiltonian eigenstates whose energy spectrum has a gap relatively to the many-electron ground state. We introduce a generalized pseudoparticle perturbation theory which describes the relevant finite-energy ground state transitions. In the present basis these excitations refer to a small density of excited pseudoparticles. Our operator basis goes beyond the Bethe-ansatz solution and it is the suitable and correct starting point for the study of the finite-frequency properties, which are of great relevance for the understanding of the unusual spectral properties detected in low-dimensional novel materials.Comment: LaTeX, 32 pages, no Figures. To be published in Phys. Rev. B (15th of August 1997

New perturbation theory of low-dimensional quantum liquids II: operator description of Virasoro algebras in integrable systems

We show that the recently developed {\it pseudoparticle operator algebra} which generates the low-energy Hamiltonian eigenstates of multicomponent integrable systems also provides a natural operator representation for the the Virasoro algebras associated with the conformal-invariant character of the low-energy spectrum of the these models. Studying explicitly the Hubbard chain in a non-zero chemical potential and external magnetic field, we establish that the pseudoparticle perturbation theory provides a correct starting point for the construction of a suitable critical-point Hamiltonian. We derive explicit expressions in terms of pseudoparticle operators for the generators of the Virasoro algebras and the energy-momentum tensor, describe the conformal-invariant character of the critical point from the point of view of the response to curvature of the two-dimensional space-time, and discuss the relation to Kac-Moody algebras and dynamical separation.Comment: 35 pages, RevteX, preprint UA

Registro, aplicación y pago del impuesto sobre la renta (IR) en Inversiones Agropecuarias S.A de Matagalpa durante el año 2015

El presente Seminario de Graduación para optar al Título de Licenciatura en Contabilidad Pública y Finanzas contiene como línea de principal de investigación y tema el Impuesto sobre la renta (IR) en las empresas de los departamentos de Matagalpa, Managua y Jinotega en el año 2015. El Subtema es Registro, aplicación y pago del impuesto sobre la Renta (IR) en Inversiones Agropecuarias S.A de Matagalpa durante el año 2015, cuya empresa es cafetalera dedica a la venta de Café en el extranjero. El objetivo del estudio es determinar la importancia de la correcta aplicación de los registros, aplicación y pago de Impuesto sobre la Renta (IR) basados en la ley 822, Ley de Concertación Tributaria vigente en la republica de Nicaragua. . Para el gremio contable que será alimentado por esta graduación es importancia analizar el Impuesto sobre la Renta IR en la ejecución de las sociedades anónimas ya que esto constituye un eje fundamental de las declaratorias de impuesto anuales a los cuales están obligados a declarar al finalizar el Periodo Fiscal. Basado en el estudio, la aplicación de instrumentos de investigación y la revisión documental se ha llegado a la conclusión principal de que Inversiones Agropecuarias S.A, está presentando las declaraciones de impuesto conforme a lo establecido en la ley 822, Ley de Concertación Tributari

Landau theory of phase separation in cuprates

I discuss the problem of phase separation in cuprates from the point of view of the Landau theory of Fermi liquids. I calculate the rate of growth of unstable regions for the hydrodymanics and collisionless limit and, in presence of long range Coulomb interactions, the size of these regions. These are analytic results valid for any strength of the Landau parameters.Comment: RevteX, preprint ITP (1994

Prostatic calculi detected in peripheral zone of the gland during a transrectal ultrasound biopsy can be significant predictors of prostate cancer

Purpose: Prostatic calculi (PC) are usually associated with benign prostatic hyperplasia or chronic inflammation. However, in several studies prostatic inflammation and calcification have been implicated in the pathogenesis of prostate cancer (CaP). We evaluated the prevalence of PC during transrectal ultrasound (TRUS) and correlate the ultrasonographic patterns with histological findings. Methods: A prospective study of 664 patients undergoing TRUS and prostate biopsy was planned. A standardized reproducible technique was used with using a GE Logiq 7 machine equipped with a 5-9MHz multi-frequency convex probe "end-fire". We defined marked presence of PC as multiple hyperechoic foci with significant area (≥ 3 mm in the largest diameter). PC were classified according to zone distribution into the gland: transitional zone (TZ), central zone (CZ), and peripheral zone (PZ). Results: No significant difference was noted between the patients with PC and without PC, when comparing age, preoperative PSA level, prostate volume, and biopsy number, except for DRE findings. 168 patients (25.3%) had marked presence of PC on TRUS: 50.6% in TZ, 20.2% in CZ, and 29.2% in PZ. 31 patients (63.3%) with presence of PC in PZ had CaP on biopsy. The correlation observed between CaP and the presence of PC in PZ was statistically significant (p < 0.001). However, among patients in the CaP group there was no statistical association between PC and moderate or high Gleason grade. Conclusions: This study suggests that chronic prostatic inflammation and PC have a role in the biogenesis of cancer. CaP was more frequent in patients with PC in PZ of the gland, but was not associated with higher Gleason grade among these patients (p < 0.001)

Finite-Temperature Transport in Finite-Size Hubbard Rings in the Strong-Coupling Limit

We study the current, the curvature of levels, and the finite temperature charge stiffness, D(T,L), in the strongly correlated limit, U>>t, for Hubbard rings of L sites, with U the on-site Coulomb repulsion and t the hopping integral. Our study is done for finite-size systems and any band filling. Up to order t we derive our results following two independent approaches, namely, using the solution provided by the Bethe ansatz and the solution provided by an algebraic method, where the electronic operators are represented in a slave-fermion picture. We find that, in the U=\infty case, the finite-temperature charge stiffness is finite for electronic densities, n, smaller than one. These results are essencially those of spinless fermions in a lattice of size L, apart from small corrections coming from a statistical flux, due to the spin degrees of freedom. Up to order t, the Mott-Hubbard gap is \Delta_{MH}=U-4t, and we find that D(T) is finite for n<1, but is zero at half-filling. This result comes from the effective flux felt by the holon excitations, which, due to the presence of doubly occupied sites, is renormalized to \Phi^{eff}=\phi(N_h-N_d)/(N_d+N_h), and which is zero at half-filling, with N_d and N_h being the number of doubly occupied and empty lattice sites, respectively. Further, for half-filling, the current transported by any eigenstate of the system is zero and, therefore, D(T) is also zero.Comment: 15 pages and 6 figures; accepted for PR