Entanglement entropy scaling in the bilayer Heisenberg spin system

We examine the entanglement properties of the spin-half Heisenberg model on the two-dimensional square-lattice bilayer based on quantum Monte Carlo calculations of the second R\'enyi entanglement entropy. In particular, we extract the dominant area-law contribution to the bipartite entanglement entropy that shows a non-monotonous behavior upon increasing the inter-layer exchange interaction: a local maximum in the area-law coefficient is located at the quantum critical point separating the antiferromagnetically ordered region from the disordered dimer-singlet regime. Furthermore, we consider subleading logarithmic corrections to the R\'enyi entanglement entropy scaling. Employing different subregion shapes, we isolate the logarithmic corner term from the logarithmic contribution due to Goldstone modes that is found to be enhanced in the limit of decoupled layers. At the quantum critical point, we estimate a contribution of $0.016(1)$ due to each $90^{\circ}$ corner. This corner term at the SU(2) quantum critical point deviates from the Gaussian theory value, while it compares well with recent numerical linked cluster calculations on the bilayer model.Comment: 7 pages, 7 figure

A R\'enyi entropy perspective on topological order in classical toric code models

Concepts of information theory are increasingly used to characterize collective phenomena in condensed matter systems, such as the use of entanglement entropies to identify emergent topological order in interacting quantum many-body systems. Here we employ classical variants of these concepts, in particular R\'enyi entropies and their associated mutual information, to identify topological order in classical systems. Like for their quantum counterparts, the presence of topological order can be identified in such classical systems via a universal, subleading contribution to the prevalent volume and boundary laws of the classical R\'enyi entropies. We demonstrate that an additional subleading $O(1)$ contribution generically arises for all R\'enyi entropies $S^{(n)}$ with $n \geq 2$ when driving the system towards a phase transition, e.g. into a conventionally ordered phase. This additional subleading term, which we dub connectivity contribution, tracks back to partial subsystem ordering and is proportional to the number of connected parts in a given bipartition. Notably, the Levin-Wen summation scheme -- typically used to extract the topological contribution to the R\'enyi entropies -- does not fully eliminate this additional connectivity contribution in this classical context. This indicates that the distillation of topological order from R\'enyi entropies requires an additional level of scrutiny to distinguish topological from non-topological $O(1)$ contributions. This is also the case for quantum systems, for which we discuss which entropies are sensitive to these connectivity contributions. We showcase these findings by extensive numerical simulations of a classical variant of the toric code model, for which we study the stability of topological order in the presence of a magnetic field and at finite temperatures from a R\'enyi entropy perspective.Comment: 17 pages, 19 figure

Influence of psychotropic drugs upon neuropsychological test performance

Commonly used psychotropic medications are widely presumed to have deleterious effects on neuropsychological test performance. However, given the special difficulties of neuropsychological assessment with psychiatric populations, these effects have rarely been directly examined for differential, quantitative effects on test scores. A comprehensive neuropsychological test battery is described that assesses executive functions, memory, language comprehension, motor and sensory functions, and manual praxis. Data are presented on 233 psychiatric patients (70 females, 163 males) referred for neuropsychological assessment. All people with known or suspected brain damage were excluded, with 100 not taking any type of psychoactive medication. Comparisons between an unmedicated group and those taking the most common medications showed differences on tests of perseverative responses and praxis. No effects for nonverbal memory, simple motor functions, basic intellectual processes or visuomotor functions were noted. Implications for the assessment of people taking psychotropic medications are discussed

Dynamical Mean Field Theory of inhomogeneous correlated systems

In the last one and a half decade, the Dynamical Mean Field Theory (DMFT) allowed to get insight into the Mott metal-insulator transition (MMIT) and many long-standing questions about the nature of the transition could be answered, at least in the limit of infinite dimensions. In this thesis, the adaption of the DMFT to inhomogeneous systems is studied, opening the possibility to study a rich variety of systems and challenging physical questions. Firstly, the basic problem is studied, how a metal penetrates into a Mott insulator, where analytically found power-laws at the critical point can be confirmed with numerics. Secondly, the phase separation between metal and insulator is investigated, which can occur since the MMIT is a first order transition. The spontaneous build up of domains is observed in numerical simulations and the domain walls are examined. Finally, the MMIT of fermionic atoms in an optical lattice is studied

Development of a Canadian adaptation of the Facts on Aging Quiz

Accurate knowledge about older adults is desirable for research into aging populations. The Palmore Facts on Aging Quiz (FAQ) has been one of the most widely used measures of knowledge about aging that has been used in English-speaking countries. The original true-false version has largely been replaced by the current multiple-choice format. Here I present data on a Canadian multiple-choice FAQ from 172 older adult residents in the community with a mean age of 70.3 years old (SD = 8.88). The mean percentage correct on the Canadian FAQ-2C was 54.4%, a proportion higher than the recent Australian data and some older American data on older adults. The Canadian adaptation of the modified Australian multiple-choice version demonstrates the value of the local verification of FAQ items’ scoring key if the knowledge assessed by the FAQ is to be used accurately in a different country or if the local scoring key was developed several years earlier

Influence of psychotropic drugs upon neuropsychological test performance

Commonly used psychotropic medications are widely presumed to have deleterious effects on neuropsychological test performance. However, given the special difficulties of neuropsychological assessment with psychiatric populations, these effects have rarely been directly examined for differential, quantitative effects on test scores. A comprehensive neuropsychological test battery is described that assesses executive functions, memory, language comprehension, motor and sensory functions, and manual praxis. Data are presented on 233 psychiatric patients (70 females, 163 males) referred for neuropsychological assessment. All people with known or suspected brain damage were excluded, with 100 not taking any type of psychoactive medication. Comparisons between an unmedicated group and those taking the most common medications showed differences on tests of perseverative responses and praxis. No effects for nonverbal memory, simple motor functions, basic intellectual processes or visuomotor functions were noted. Implications for the assessment of people taking psychotropic medications are discussed