Some properties of frustrated spin systems: extensions and applications of Lieb-Schupp approach

Lieb and Schupp have obtained, using certain version of ``spin-reflection positivity'' method, a number of ground-state properties for frustrated Heisenberg models. One group of these results is related to singlet nature of ground state and it needs an assumption of reflection symmetry present in the system. In this paper, it is shown that the result holds also for other symmetries (inversion etc.). The second Lieb-Schupp result is relation between ground-state energies of certain systems. In the paper, this relation is applied to multidimensional models on various lattices.Comment: 15 pages, 8 eps figures, revtex

Spin-charge-orbital ordering on triangle-based lattices

We investigate the ground-state property of an e_g-orbital Hubbard model at quarter filling on a zigzag chain by exploiting the density matrix renormalization group method. When two orbitals are degenerate, the zigzag chain is decoupled to a doble-chain spin system to suppress the spin frustration due to the spatial anisotropy of the occupied orbital. On the other hand, when the level splitting is increased and the orbital anisotropy disappears, a characteristic change in the spin incommnsurability is observed due to the revival of the spin frustration.Comment: 2 pages, 1 figure, Proceedings of SCES'05 (July 26-30, 2005, Vienna

Virtual Desktop Sizing

This paper is intended to describe a process of choosing and building a demo of virtualization solution for a group of people in campus of EPFL located in a city of Sion, Valais Wallis. The aim of the paper is to compare different desktop virtualization solutions and choose the best one within the given customer’s requirements and infrastructure. The second goal of the paper is to provide a demo implementation of the selected virtualization solution with guidelines describing how it was created and notes on specific customizations required within the given internal computer structure of the campus

On the definition of temperature using time--averages

This paper is a natural continuation of a previous one by the author, which was concerned with the foundations of statistical thermodynamics far from equilibrium. One of the problems left open in that paper was the correct definition of temperature. In the literature, temperature is in general defined through the mean kinetic energy of the particles of a given system. In this paper, instead, temperature is defined "a la Caratheodory", the system being coupled to a heat bath, and temperature being singled out as the ``right'' integrating factor of the exchanged heat. As a byproduct, the ``right'' expression for the entropy is also obtained. In particular, in the case of a q-distributions the entropy turns out to be that of Tsallis, which we however show to be additive, at variance with what is usually maintained

The structure of a far-red fluorescent protein, AQ143, shows evidence in support of reported red-shifting chromophore interactions

Engineering fluorescent proteins (FPs) to emit light at longer wavelengths is a significant focus in the development of the next generation of fluorescent biomarkers, as far-red light penetrates tissue with minimal absorption, allowing better imaging inside of biological hosts. Structure-guided design and directed evolution have led to the discovery of red FPs with significant bathochromic shifts to their emission. Here, we present the crystal structure of one of the most bathochromically shifted FPs reported to date, AQ143, a nine-point mutant of aeCP597, a chromoprotein from Actinia equina. The 2.19 Å resolution structure reveals several important chromophore interactions that contribute to the protein's far-red emission and shows dual occupancy of the green and red chromophores

Enterprise Web Application Usability Testing with Following Implementation of Findings

Today the competitive online market requires a web application to be user-friendly and intuitive. Following usability principles during the application development process is a key for application to succeed. That’s why usability principles should be learnt and followed by the whole development team. The goal of the thesis is to conduct the usability testing and improve an enterprise web application for Good Sign Oy in order to increase the quality of the product and enhance customer satisfaction with the product. The project includes full usability testing lifecycle and the process of findings implementation

The scattered debris of the Magellanic Stream

Searching the HI Parkes All-Sky Survey (HIPASS) and its northern extension, we detected a population of very compact high-velocity clouds (HVCs) with similar velocities in the Galactic standard-of-rest frame which appear to be arranged in several filaments aligned with the nearby Magellanic Stream. A comparison with published OVI/CaII absorption and HI emission line measurements suggests that the HVCs are condensations within an extended and mainly ionised component of the Magellanic Stream. They coincide in position with a faint gas stream predicted in numerical simulations of the Magellanic Clouds by Gardiner & Noguchi (1996). Consequently, the Magellanic Stream could be much more extended than generally believed.Comment: 5 pages, 4 figures, accepted for publication in MNRA

Prevailing Academic View on Compliance Flexibility under § 111 of the Clean Air Act

No colons in abstractsource category, existing sources, state implementation plan, new sources, tradable performance standards

Contact Terms and Duality Symmetry in The Critical Dissipative Hofstadter Model

The dissipative Hofstadter model describes the quantum mechanics of a charged particle in two dimensions subject to a periodic potential, uniform magnetic field, and dissipative force. Its phase diagram exhibits an SL(2,Z) duality symmetry and has an infinite number of critical circles in the dissipation/magnetic field plane. In addition, multi-critical points on a particular critical circle correspond to non-trivial solutions of open string theory. The duality symmetry is expected to provide relations between correlation functions at different multi-critical points. Many of these correlators are contact terms. However we expect them to have physical significance because under duality they transform into functions that are non-zero for large separations of the operators. Motivated by the search for exact, regulator independent solutions for these contact terms, in this paper we derive many properties and symmetries of the coordinate correlation functions at the special multi-critical points. In particular, we prove that the correlation functions are homogeneous, piecewise-linear functions of the momenta, and we prove a weaker version of the anticipated duality transformation. Consequently, the possible forms of the correlation functions are limited to lie in a finite dimensional linear space. We treat the potential perturbatively and these results are valid to all orders in perturbation theory.Comment: 65 pages, six figures, CTP#217

Bias driven coherent carrier dynamics in a two-dimensional aperiodic potential

We study the dynamics of an electron wave-packet in a two-dimensional square lattice with an aperiodic site potential in the presence of an external uniform electric field. The aperiodicity is described by $\epsilon_{\bf m} = V\cos{(\pi\alpha m_x^{\nu_x})}\cos{(\pi\alpha m_y^{\nu_y})}$ at lattice sites $(m_x, m_y)$, with $\pi \alpha$ being a rational number, and $\nu_x$ and $\nu_y$ tunable parameters, controlling the aperiodicity. Using an exact diagonalization procedure and a finite-size scaling analysis, we show that in the weakly aperiodic regime ($\nu_x,\nu_y < 1$), a phase of extended states emerges in the center of the band at zero field giving support to a macroscopic conductivity in the thermodynamic limit. Turning on the field gives rise to Bloch oscillations of the electron wave-packet. The spectral density of these oscillations may display a double peak structure signaling the spatial anisotropy of the potential landscape. The frequency of the oscillations can be understood using a semi-classical approach.Comment: 16 pages, to appear in Phys. Lett.