Single particle spectrum of the flux phase in the FM Kondo Model

We investigate the 2D ferromagnetic Kondo lattice model for manganites with classical corespins at Hund's rule coupling J_H=6, with antiferromagnetic superexchange 0.03 < J' < 0.05. We employ canonical and grand canonical unbiased Monte Carlo simulations and find paramagnetism, weak ferromagnetism and the Flux phase, depending on doping and on J'. The observed single particle spectrum in the flux phase differs from the idealized infinite lattice case, but agrees well with an idealized finite lattice case with thermal fluctuations.Comment: contribution to the SCES04 conferenc

Testing for Non-Linear Dependence in Univariate Time Series: An Empirical Investigation of the Austrian Unemployment Rate

The modelling of univariate time series is a subject of great importance in a variety of fields, in regional science and economics, and beyond. Time series modelling involves three major stages:model identification, model%0D estimation and diagnostic checking. This current paper focuses its attention on the model identification stage in general and on the issue of testing for non-linear dependence in particular. If the null hypothesis of independence is rejected, then the alternative hypothesis implies the existence of linear or non-linear dependence. The test of this hypothesis is of crucial importance. If the data are linearly dependent, the linear time series models have to be specified (generally within the SARIMA methodology). If the data are non-linearly dependent, then non-linear time series modelling (such as ARCH, GARCH and autoregressive neural network models) must be employed. Several tests have recently been developed for this purpose. In this paper we make a modest attempt to investigate the power of five competing tests (McLeod-Li-test, Hsieh-test, BDS-test, Terävirta''''s neural network test) in a real world application domain of unemployment rate prediction in order to determine what kind of non-linear specification they have good power against, and which not. The results obtained indicate that that all the tests reject the hypothesis of mere linear dependence in our application. But if interest is focused on predicting the conditional mean of the series, the neural network test is most informative for model identification and its use is therefore highly%0D recommended.

Modeling Latent Variable Uncertainty for Loss-based Learning

We consider the problem of parameter estimation using weakly supervised datasets, where a training sample consists of the input and a partially specified annotation, which we refer to as the output. The missing information in the annotation is modeled using latent variables. Previous methods overburden a single distribution with two separate tasks: (i) modeling the uncertainty in the latent variables during training; and (ii) making accurate predictions for the output and the latent variables during testing. We propose a novel framework that separates the demands of the two tasks using two distributions: (i) a conditional distribution to model the uncertainty of the latent variables for a given input-output pair; and (ii) a delta distribution to predict the output and the latent variables for a given input. During learning, we encourage agreement between the two distributions by minimizing a loss-based dissimilarity coefficient. Our approach generalizes latent SVM in two important ways: (i) it models the uncertainty over latent variables instead of relying on a pointwise estimate; and (ii) it allows the use of loss functions that depend on latent variables, which greatly increases its applicability. We demonstrate the efficacy of our approach on two challenging problems---object detection and action detection---using publicly available datasets.Comment: ICML201

Beyond the Spin Model Approximation for Ramsey Spectroscopy

Ramsey spectroscopy has become a powerful technique for probing non-equilibrium dynamics of internal (pseudospin) degrees of freedom of interacting systems. In many theoretical treatments, the key to understanding the dynamics has been to assume the external (motional) degrees of freedom are decoupled from the pseudospin degrees of freedom. Determining the validity of this approximation -- known as the spin model approximation -- is complicated, and has not been addressed in detail. Here we shed light in this direction by calculating Ramsey dynamics exactly for two interacting spin-1/2 particles in a harmonic trap. We focus on $s$-wave-interacting fermions in quasi-one and two-dimensional geometries. We find that in 1D the spin model assumption works well over a wide range of experimentally-relevant conditions, but can fail at time scales longer than those set by the mean interaction energy. Surprisingly, in 2D a modified version of the spin model is exact to first order in the interaction strength. This analysis is important for a correct interpretation of Ramsey spectroscopy and has broad applications ranging from precision measurements to quantum information and to fundamental probes of many-body systems

Insuring the Healthy or Insuring the Sick? The Dilemma of Regulating the Individual Health Insurance Market -- Short Case Studies of Six States

Looks at a range of regulatory strategies used to make individual health insurance policies more accessible and affordable. Assesses the effectiveness of regulatory reforms in Iowa, Kansas, Kentucky, Massachusetts, New Jersey, and Washington

Phase diagram for the one-dimensional Hubbard-Holstein model: A density-matrix renormalization group study

Phase diagram of the Hubbard-Holstein model in the coexistence of electron-electron and electron-phonon interactions has been theoretically obtained with the density-matrix renormalization group method for one-dimensional (1D) systems, where an improved warm-up (the recursive sweep) procedure has enabled us to calculate various correlation functions. We have examined the cases of (i) the systems half-filled by electrons for the full parameter space spanned by the electron-electron and electron-phonon coupling constants and the phonon frequency, (ii) non-half-filled system, and (iii) trestle lattice. For (i), we have detected a region where both the charge and on-site pairing correlations decay with power-laws in real space, which suggests a metallic behavior. While pairing correlations are not dominant in (i), we have found that they become dominant as the system is doped in (ii), or as the electronic band structure is modified (with a broken electron-hole symmetry) in (iii) in certain parameter regions.Comment: 12 pages, 14 figures, submitted to Phys. Rev.

The Flower of Human Perfection: Moses Mendelssohn\u27s Defense of Rationalist Aesthetics

This work is an analysis of Moses Mendelssohn\u27s contributions to aesthetic rationalism, a tradition that arose in 18-century Germany. Rationalists held that aesthetic experience is primarily explained by the perfection of the object being considered, where perfection is a fundamental, rational (law-governed) property. As this work shows, Mendelssohn was among the first to acknowledge and effectively address several significant objections to the rationalist theory: its seeming inability to account for pleasure generally, tragedy and tragic pleasure more specifically, and the sublime; and its apparent blindness to the claims of genius and Rousseau\u27s ethical critique of the arts. Many commentators have claimed that Mendelssohn saw these issues as reasons to move away from aesthetic rationalism, but Mendelssohn in fact attempted to address each of them from within the rationalist framework. Mendelssohn\u27s resulting elaboration and defense of the rationalist tradition illustrates its resilience and lasting relevance

The Effect of Personalized Vocabulary Plans on Learner Autonomy in L2 Vocabulary Learning

Autonomy involves learners taking responsibility and control of their language learning. A great deal of language learning happens outside of the walls of the classroom. So for language learners to succeed and continue beyond their ESL courses, they must at some point take charge of their learning process. In explicit vocabulary learning, learner autonomy can be promoted by giving the learner choices, providing input on planning and recording methods, teaching useful review strategies and encouraging reflective practice. Personalization has been proposed as a potentially significant propellant for learner autonomy in language learning for decades. It has recently come to the forefront of the conversation in general education as well. This research builds on studies showing a connection between the use of vocabulary notebooks and autonomy while looking more closely at the relationship between personalization and autonomy in L2 vocabulary learning. The primary question for this research was: Will ESL learners benefit from developing their own personalized vocabulary learning plan (PVP) that is based on their starting vocabulary level, perceived needs and personal vocabulary goals? The conclusion was that most participants did benefit in some key areas, though not all. The PVP was a useful tool in developing learner autonomy when used for planning, student-teacher collaboration and reflective practices. Additionally, this study provides evidence that, for some aspects of vocabulary learning, there is a relationship between a learner’s perception of ability and the degree of responsibility he or she assumes. This study confirms that one way to encourage learners to become more autonomous is to increase their confidence in their own abilities

Effects of scopolamine on matching to sample paradigm and related tests in human subjects

This was a double-blind placebo-controlled study with a cross-over design to examine the effects of scopolamine on cognitive functions in young healthy subjects. Scopolamine hydrobromide was administered subcutaneously to 12 subjects (mean +/- SD age 23.8 +/- 2.2 years) at doses of 0.3 and 0.6 mg in comparison with two placebo conditions. Scopolamine at both doses produced marked sedation as rated by subjects and an observer. In the continuous performance test, vigilance was impaired by both doses of scopolamine. The span of apprehension test showed differing results (only the high dose of scopolamine showed a performance decrement only in the three-character version of the span of apprehension test). Significant impairment by both doses of scopolamine was seen in immediate and delayed free recall, continuous visual recognition, running word recognition and running picture recognition. While scopolamine caused a significant slowing in average reaction times for simultaneous matching as well as for delayed matching, subjects made more errors under scopolamine compared to placebo only in delayed matching, not in simultaneous matching. Also, the main outcome of matching to sample showed significant effects only in delayed matching, not in simultaneous matching. Notable in this study is the incongruity between the simultaneous matching test and the span of apprehension test on the one hand and the other cognitive tests used on the other. These results demonstrated that scopolamine has a greater effect on memory than on attention. Thus, the scopolamine-induced effects in the present study seem to be more relevant to Alzheimer's disease in an advanced phase than to normal aging. Copyright (C) 2003 S. Karger AG, Basel