Analytical ground state for the three-band Hubbard model

For the calculation of charge excitations as those observed in, e.g., photo-emission spectroscopy or in electron-energy loss spectroscopy, a correct description of ground-state charge properties is essential. In strongly correlated systems like the undoped cuprates this is a highly non-trivial problem. In this paper we derive a non-perturbative analytical approximation for the ground state of the three-band Hubbard model on an infinite, half filled CuO_2 plane. By comparison with Projector Quantum Monte Carlo calculations it is shown that the resulting expressions correctly describe the charge properties of the ground state. Relations to other approaches are discussed. The analytical ground state preserves size consistency and can be generalized for other geometries, while still being both easy to interpret and to evaluate.Comment: REVTeX, 8 pages, 6 figures, to appear in Phys. Rev.

Prevalence and significance of alterations in cardiac structure and function in patients with heart failure and a preserved ejection fraction

<p><b>Background:</b> The purpose of this study was to examine the prevalence of abnormalities in cardiac structure and function present in patients with heart failure and a preserved ejection fraction (HFPEF) and to determine whether these alterations in structure and function were associated with cardiovascular morbidity and mortality.</p> <p><b>Methods and Results:</b> The Irbesartan in HFPEF trial (I-PRESERVE) enrolled 4128 patients; echocardiographic determination of left ventricular (LV) volume, mass, left atrial (LA) size, systolic function, and diastolic function were made at baseline in 745 patients. The primary end point was death or protocol-specific cardiovascular hospitalization. A secondary end point was the composite of heart failure death or heart failure hospitalization. Associations between baseline structure and function and patient outcomes were examined using univariate and multivariable Cox proportional hazard analyses. In this substudy, LV hypertrophy or concentric remodeling was present in 59%, LA enlargement was present in 66%, and diastolic dysfunction was present in 69% of the patients. Multivariable analyses controlling for 7 clinical variables (including log N-terminal pro-B–type natriuretic peptide) indicated that increased LV mass, mass/volume ratio, and LA size were independently associated with an increased risk of both primary and heart failure events (all P<0.05).</p> <p><b>Conclusions:</b> Left ventricular hypertrophy or concentric remodeling, LA enlargement, and diastolic dysfunction were present in the majority of patients with HFPEF. Left ventricular mass and LA size were independently associated with an increased risk of morbidity and mortality. The presence of structural remodeling and diastolic dysfunction may be useful additions to diagnostic criteria and provide important prognostic insights in patients with HFPEF.</p&gt

Мероприятия по уменьшению потерь при транспортировке природного газа

В газораспределительной сети имеют место производственно-технологические потери природного газа, как нормированные, так и сверхнормативные. В связи с развитием газификации (увеличением протяженности газопроводов, ростом количества газифицированных квартир, объектов и т.д.), старением газопроводов и изношенностью оборудования нормированные потери газа в газораспределительных сетях немного повысятся и к 2030 году составят около 2% от объёмов потребления. Ожидается, что потери природного газа в газотранспортной системе в 2030 году достигнут уровня 0,3% от объёмов его транспортировки. В работе рассмотрены виды и источники технологических потерь природного газа, изучены способы их уменьшения при транспортировке по магистральным газопроводам.In gas-distributing network there can be normalized and above-standard production and technological losses of natural gas. Due to the development of gasification (the extension of gas pipelines, a growing number of gasified apartments, facilities, etc.), ageing of gas pipelines and the depreciation of equipment normalized-losses of gas in gas distribution networks will increase slightly in 2030 will be about 2% of the volume of consumption. It is expected that losses of natural gas in the transmission system in 2030 will reach the level of 0.3% of total transport. The article discusses the types and sources of technological losses of natural gas, studied ways to reduce them during transportation through trunk gas pipelines

Phase Transition in the Three-Dimensional ±J\pm J Ising Spin Glass

We have studied the three-dimensional Ising spin glass with a $\pm J$ distribution by Monte Carlo simulations. Using larger sizes and much better statistics than in earlier work, a finite size scaling analysis shows quite strong evidence for a finite transition temperature, $T_c$, with ordering below $T_c$. Our estimate of the transition temperature is rather lower than in earlier work, and the value of the correlation length exponent, $\nu$, is somewhat higher. Because there may be (unknown) corrections to finite size scaling, we do not completely rule out the possibility that $T_c = 0$ or that $T_c$ is finite but with no order below $T_c$. However, from our data, these possibilities seem less likely.Comment: Postscript file compressed using uufiles. The postscript file is also available by anonymous ftp at ftp://chopin.ucsc.edu/pub/sg3d.p

Kinetic Inductance of Josephson Junction Arrays: Dynamic and Equilibrium Calculations

We show analytically that the inverse kinetic inductance $L^{-1}$ of an overdamped junction array at low frequencies is proportional to the admittance of an inhomogeneous equivalent impedance network. The $ij^{th}$ bond in this equivalent network has an inverse inductance $J_{ij}\cos(\theta_i^0-\theta_j^0-A_{ij})$, where $J_{ij}$ is the Josephson coupling energy of the $ij^{th}$ bond, $\theta_i^0$ is the ground-state phase of the grain $i$, and $A_{ij}$ is the usual magnetic phase factor. We use this theorem to calculate $L^{-1}$ for square arrays as large as $180\times 180$. The calculated $L^{-1}$ is in very good agreement with the low-temperature limit of the helicity modulus $\gamma$ calculated by conventional equilibrium Monte Carlo techniques. However, the finite temperature structure of $\gamma$, as a function of magnetic field, is \underline{sharper} than the zero-temperature $L^{-1}$, which shows surprisingly weak structure. In triangular arrays, the equilibrium calculation of $\gamma$ yields a series of peaks at frustrations $f = \frac{1}{2}(1-1/N)$, where $N$ is an integer $\geq 2$, consistent with experiment.Comment: 14 pages + 6 postscript figures, 3.0 REVTe

Combining 10Be surface exposure and OSL dating to reconstruct Holocene lake-level fluctuations: a case study at Tangra Yumco (southern Tibet)

Abstract HKT-ISTP 2013 B

Superconductivity in striped and multi-Fermi-surface Hubbard models: From the cuprates to the pnictides

Single- and multi-band Hubbard models have been found to describe many of the complex phenomena that are observed in the cuprate and iron-based high-temperature superconductors. Simulations of these models therefore provide an ideal framework to study and understand the superconducting properties of these systems and the mechanisms responsible for them. Here we review recent dynamic cluster quantum Monte Carlo simulations of these models, which provide an unbiased view of the leading correlations in the system. In particular, we discuss what these simulations tell us about superconductivity in the homogeneous 2D single-orbital Hubbard model, and how charge stripes affect this behavior. We then describe recent simulations of a bilayer Hubbard model, which provides a simple model to study the type and nature of pairing in systems with multiple Fermi surfaces such as the iron-based superconductors.Comment: Published as part of Superstripes 2011 (Rome) conference proceeding