High temperature thermal conductivity of 2-leg spin-1/2 ladders

Based on numerical simulations, a study of the high temperature, finite frequency, thermal conductivity $\kappa(\omega)$ of spin-1/2 ladders is presented. The exact diagonalization and a novel Lanczos technique are employed.The conductivity spectra, analyzed as a function of rung coupling, point to a non-diverging $dc-$limit but to an unconventional low frequency behavior. The results are discussed with perspective recent experiments indicating a significant magnetic contribution to the energy transport in quasi-one dimensional compounds.Comment: 4 pages, 4 figure

Thermal transport of the XXZ chain in a magnetic field

We study the heat conduction of the spin-1/2 XXZ chain in finite magnetic fields where magnetothermal effects arise. Due to the integrability of this model, all transport coefficients diverge, signaled by finite Drude weights. Using exact diagonalization and mean-field theory, we analyze the temperature and field dependence of the thermal Drude weight for various exchange anisotropies under the condition of zero magnetization-current flow. First, we find a strong magnetic field dependence of the Drude weight, including a suppression of its magnitude with increasing field strength and a non-monotonic field-dependence of the peak position. Second, for small exchange anisotropies and magnetic fields in the massless as well as in the fully polarized regime the mean-field approach is in excellent agreement with the exact diagonalization data. Third, at the field-induced quantum critical line between the para- and ferromagnetic region we propose a universal low-temperature behavior of the thermal Drude weight.Comment: 9 pages REVTeX4 including 5 figures, revised version, refs. added, typos correcte

Этиопатогенетические аспекты терапии хронических воспалительных заболеваний органов малого таза

Наведено сучасні принципи лікування запальних захворювань жіночих статевих органів з урахуванням етіопатогенезу запалення й особливостей продукції у цервікальному слизу запальних і протизапальних цитокинів. Показано, що включення до комплексу терапії інтерферонів сприяє відновленню порушеного імунологічного гомеостазу й зниженню ймовірності рецидивів захворювання.Modern principles of treatment of inflammatory diseases of female genitals taking into account an etiopathogenesis of an inflammation and features of production in сervical mucous inflammatory and antiinflammatory cytokines are resulted. Including in a complex of therapy of interferons is shown, that, promotes restoration of the broken immunologic homeostasis and depression of probability of relapses of disease

Log-periodic corrections to scaling: exact results for aperiodic Ising quantum chains

Log-periodic amplitudes of the surface magnetization are calculated analytically for two Ising quantum chains with aperiodic modulations of the couplings. The oscillating behaviour is linked to the discrete scale invariance of the perturbations. For the Fredholm sequence, the aperiodic modulation is marginal and the amplitudes are obtained as functions of the deviation from the critical point. For the other sequence, the perturbation is relevant and the critical surface magnetization is studied.Comment: 12 pages, TeX file, epsf, iopppt.tex, xref.tex which are joined. 4 postcript figure

Exact two-spinon dynamical correlation function of the Heisenberg model

We derive the exact contribution of two spinons to the dynamical correlation function of the spin-1/2 Heisenberg model. For this, we use the isotropic limits of the exact form factors that have been recently computed through the quantum affine symmetry of the anisotropic Heisenberg model $XXZ$Comment: 9 pages, Latex, 2 corrections of coefficient

The Oscillatory Behavior of the High-Temperature Expansion of Dyson's Hierarchical Model: A Renormalization Group Analysis

We calculate 800 coefficients of the high-temperature expansion of the magnetic susceptibility of Dyson's hierarchical model with a Landau-Ginzburg measure. Log-periodic corrections to the scaling laws appear as in the case of a Ising measure. The period of oscillation appears to be a universal quantity given in good approximation by the logarithm of the largest eigenvalue of the linearized RG transformation, in agreement with a possibility suggested by K. Wilson and developed by Niemeijer and van Leeuwen. We estimate $\gamma$ to be 1.300 (with a systematic error of the order of 0.002) in good agreement with the results obtained with other methods such as the $\epsilon$-expansion. We briefly discuss the relationship between the oscillations and the zeros of the partition function near the critical point in the complex temperature plane.Comment: 21 pages, 10 Postcript figures, latex file, uses revte

Phase diagram of self-assembled rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations

Monte Carlo simulations and finite-size scaling analysis have been carried out to study the critical behavior in a two-dimensional system of particles with two bonding sites that, by decreasing temperature or increasing density, polymerize reversibly into chains with discrete orientational degrees of freedom and, at the same time, undergo a continuous isotropic-nematic (IN) transition. A complete phase diagram was obtained as a function of temperature and density. The numerical results were compared with mean field (MF) and real space renormalization group (RSRG) analytical predictions about the IN transformation. While the RSRG approach supports the continuous nature of the transition, the MF solution predicts a first-order transition line and a tricritical point, at variance with the simulation results.Comment: 12 pages, 10 figures, supplementary informatio

The use of indigenous knowledge in development: problems and challenges

The use of indigenous knowledge has been seen by many as an alternative way of promoting development in poor rural communities in many parts of the world. By reviewing much of the recent work on indigenous knowledge, the paper suggests that a number of problems and tensions has resulted in indigenous knowledge not being as useful as hoped for or supposed. These include problems emanating from a focus on the (arte)factual; binary tensions between western science and indigenous knowledge systems; the problem of differentiation and power relations; the romanticization of indigenous knowledge; and the all too frequent decontextualization of indigenous knowledge

Thermal conductivity and specific heat of the linear chain cuprate Sr2_{2}CuO3_{3}: Evidence for thermal transport via spinons

We report measurements of the specific heat and the thermal conductivity of the model Heisenberg spin-1/2 chain cuprate Sr$_{2}$CuO$_{3}$ at low temperatures. In addition to a nearly isotropic phonon heat transport, we find a quasi one-dimensional excess thermal conductivity along the chain direction, most likely associated with spin excitations (spinons). The spinon energy current is limited mainly by scattering on defects and phonons. Analyzing the specific heat data, the intrachain magnetic exchange $J/k_{B}$ is estimated to be 2650 K.Comment: 4 RevTeX pages, 3 figures, to appear in Phys. Rev.