Self-energy flows in the two-dimensional repulsive Hubbard model

We study the two-dimensional repulsive Hubbard model by functional RG methods, using our recently proposed channel decomposition of the interaction vertex. The main technical advance of this work is that we calculate the full Matsubara frequency dependence of the self-energy and the interaction vertex in the whole frequency range without simplifying assumptions on its functional form, and that the effects of the self-energy are fully taken into account in the equations for the flow of the two-body vertex function. At Van Hove filling, we find that the Fermi surface deformations remain small at fixed particle density and have a minor impact on the structure of the interaction vertex. The frequency dependence of the self-energy, however, turns out to be important, especially at a transition from ferromagnetism to d-wave superconductivity. We determine non-Fermi-liquid exponents at this transition point.Comment: 48 pages, 18 figure

Functional renormalization and mean-field approach to multiband systems with spin-orbit coupling: Application to the Rashba model with attractive interaction

The functional renormalization group (RG) in combination with Fermi surface patching is a well-established method for studying Fermi liquid instabilities of correlated electron systems. In this article, we further develop this method and combine it with mean-field theory to approach multiband systems with spin-orbit coupling, and we apply this to a tight-binding Rashba model with an attractive, local interaction. The spin dependence of the interaction vertex is fully implemented in a RG flow without SU(2) symmetry, and its momentum dependence is approximated in a refined projection scheme. In particular, we discuss the necessity of including in the RG flow contributions from both bands of the model, even if they are not intersected by the Fermi level. As the leading instability of the Rashba model, we find a superconducting phase with a singlet-type interaction between electrons with opposite momenta. While the gap function has a singlet spin structure, the order parameter indicates an unconventional superconducting phase, with the ratio between singlet and triplet amplitudes being plus or minus one on the Fermi lines of the upper or lower band, respectively. We expect our combined functional RG and mean-field approach to be useful for an unbiased theoretical description of the low-temperature properties of spin-based materials.Comment: consistent with published version in Physical Review B (2016

Relationship characteristics as moderators of the satisfaction-loyalty link : findings in a business-to-business context

Our paper is organized as follows. We begin with a brief overview of the theoretical and conceptual background of our study and provide a synthesis of the extant empirical literature on the relationship between customer satisfaction and customer loyalty. We discuss relationship characteristics as possible moderators of this link and develop research hypotheses. Next, we discuss the method employed to test these hypotheses and present our results. We conclude with a discussion of our results and its implications for future academic research and managers

Personal Characteristics as Moderators of the Relationship Between Customer Satisfaction and Loyalty - An Empirical Analysis

Previous research on the relationship between customer satisfaction and loyalty has largely neglected the issue of moderator variables. The authors develop a set of hypotheses related to the moderating effect of selected personal characteristics on the satisfaction-loyalty link. These hypotheses are tested in a consumer durables context using multiple group causal analysis. Empirical findings provide reasonable support for the theoretical arguments. Specifically, variety seeking, age, and income are found to be important moderators of the satisfaction-loyalty relationship

A novel framework to harmonise satellite data series for climate applications

Fundamental and thematic climate data records derived from satellite observations provide unique information for climate monitoring and research. Since any satellite operates over a limited period of time only, creating a climate data record requires the combination of space-borne measurements from a series of several (often similar) satellite sensors. A simple combination of calibrated measurements from several sensors, however, can produce an inconsistent climate data record. This is particularly true of older, historic sensors whose behavior in space was often different from their behavior during pre-launch calibration in the laboratory. More scientific value can be derived from considering the series of historical and present satellites as a whole. Here we consider harmonisation as a process that obtains new calibration coefficients for revised sensor calibration models by comparing calibrated measurements over appropriate satellite-to-satellite match-ups, such as simultaneous nadir overpasses. When we perform a comparison of two sensors, however, we must consider that those sensors are not observing exactly the same Earth radiance. This is in part due to differences in exact location and time tolerated by the match-up process itself, but also due to differences in the spectral response functions of the two instruments, even when nominally observing the same spectral band. To derive a harmonised data set we do not aim to correct for spectral response function differences, but to reconcile the calibration of different sensors given their estimated spectral response function differences. Here we present the concept of a framework that establishes calibration coefficients and their uncertainty and error covariance for an arbitrary number of sensors in a metrologically-rigorous manner. We describe harmonisation and its mathematical formulation as an inverse problem. Solving this problem is challenging when some hundreds of millions of match-ups are involved and the errors of fundamental sensor measurements are correlated. We solve the harmonisation problem as marginalised errors in variables regression. The algorithm involves computation of first and second order partial derivatives, for which the corresponding computer source code is generated by Automatic Differentiation. Finally we present re-calibrated AVHRR radiances from a series of 10 sensors. It is shown that the new time series have much less match-up differences while being consistent with uncertainty statistics

Random quantum Ising chains with competing interactions

In this paper we discuss the criticality of a quantum Ising spin chain with competing random ferromagnetic and antiferromagnetic couplings. Quantum fluctuations are introduced via random local transverse fields. First we consider the chain with couplings between first and second neighbors only and then generalize the study to a quantum analog of the Viana-Bray model, defined on a small world random lattice. We use the Dasgupta-Ma decimation technique, both analytically and numerically, and focus on the scaling of the lattice topology, whose determination is necessary to define any infinite disorder transition beyond the chain. In the first case, at the transition the model renormalizes towards the chain, with the infinite disorder fixed point described by Fisher. This corresponds to the irrelevance of the competition induced by the second neighbors couplings. As opposed to this case, this infinite disorder transition is found to be unstable towards the introduction of an arbitrary small density of long range couplings in the small world models

Glaciological characterization of Chile

Se realizó una caracterización glaciológica de Chile, la cual incluyó la determinación del número, superficie y el equivalente en agua contenida en los glaciares a nivel nacional (Incluidos los glaciares rocosos y campos de hielo patagónicos). La caracterización glaciológica de Chile se realizó mediante datos extraídos del Inventario Nacional de Glaciares de la Dirección General de Aguas (DGA) con actualización al año 2014, generación de información en base a procesamiento del inventario de glaciares e información bibliográfica. Dentro de los resultados, se pudo establecer que Chile posee un total estimado de 24.114 glaciares con una superficie de 23.641 km2. No obstante, esta cantidad de hielo se manifiesta con grandes diferencias regionales a lo largo del país, aumentando de norte a sur. El equivalente en agua contenida de todos los cuerpos de hielo a nivel nacional corresponde a un total estimado de 3.175 km3.An analysis of Chilean glaciers was carried out which included determining the number, surface and water content of glaciers across the country (including rock glaciers and Patagonian ice fields). Chile’s glaciological depiction was performed with data obtained from the National Inventory of Glaciers of the General Directorate of Water (Dirección General de Aguas - DGA) and bibliographic information. From the results, it was established that Chile has an estimated total of 24,114 glaciers with a surface of 23,641km2. Nevertheless, this surface of ice has great regional differences across the country, covering more surface area in the south. The equivalent water content of all ice bodies in the country has been estimated at 3,175 km3