Critical Behaviour of a Fermionic Random Matrix Model at Large-N

We study the large-$N$ limit of adjoint fermion one-matrix models. We find one-cut solutions of the loop equations for the correlators of these models and show that they exhibit third order phase transitions associated with $m$-th order multi-critical points with string susceptibility exponents $\gamma_{\rm str}=-1/m$. We also find critical points which can be interpreted as points of first order phase transitions, and we discuss the implications of this critical behaviour for the topological expansion of these matrix models.Comment: 14 pages LaTeX; UBC/S-94/

Large N QCD in two dimensions with a baryonic chemical potential

We consider large N gauge theory on a two dimensional lattice in the presence of a baryonic chemical potential. We work with one copy of naive fermion and argue that reduction holds even in the presence of a chemical potential. Analytical arguments supported by numerical studies show that there is no phase transition as a function of the baryonic chemical potential.Comment: 12 pages, 4 figures; Published version, typos correcte

Spin Hall magnetoresistance in antiferromagnet/heavy-metal heterostructures

We investigate the spin Hall magnetoresistance in thin film bilayer heterostructures of the heavy metal Pt and the antiferromagnetic insulator NiO. While rotating an external magnetic field in the easy plane of NiO, we record the longitudinal and the transverse resistivity of the Pt layer and observe an amplitude modulation consistent with the spin Hall magnetoresistance. In comparison to Pt on collinear ferrimagnets, the modulation is phase shifted by 90{\deg} and its amplitude strongly increases with the magnitude of the magnetic field. We explain the observed magnetic field-dependence of the spin Hall magnetoresistance in a comprehensive model taking into account magnetic field induced modifications of the domain structure in antiferromagnets. With this generic model we are further able to estimate the strength of the magnetoelastic coupling in antiferromagnets. Our detailed study shows that the spin Hall magnetoresistance is a versatile tool to investigate the magnetic spin structure as well as magnetoelastic effects, even in antiferromagnetic multidomain materials

Pain Experiences and Their Relation to Opioid Misuse Risk and Emotion Dysregulation

Pain is a complex, multidimensional experience but often is measured as a unidimensional experience. This study aimed to separately assess the sensory and affective components of pain and identify their relations to important pain-related outcomes, particularly in terms of opioid misuse risk and emotion dysregulation among patients with chronic pain receiving treatment in Appalachia. Two hundred and twelve patients presenting to a multidisciplinary pain center completed the Difficulties in Emotion Regulation Scale (DERS-18), Screener and Opioid Assessment for Patients with Pain—Revised (SOAPP-R), and short-form McGill Pain Questionnaire (SF-MPQ). The sensory experience of pain was unrelated to emotion dysregulation (r = 0.06, p = 0.57) and weakly related to opioid misuse risk (r = 0.182, p \u3c 0.05). In contrast, the affective experience of pain was moderately related to emotion dysregulation (r = 0.217, p \u3c 0.05) and strongly related to opioid misuse risk (r = 0.37, p \u3c 0.01). In addition, emotion dysregulation predicted variance in opioid misuse risk above and beyond the affective and sensory experiences of pain ((b = 0.693, p \u3c 0.001). The results suggest patients with a strong affective experience versus sensory experience of pain and challenges with emotion regulation may require a more comprehensive intervention to address these underlying components in order to reduce their risk of misusing opioid medications

Employment Gains from Minimum-Wage Hikes under Perfect Competition: A Simple General-Equilibrium Analysis

Contrary to conventional wisdom, higher minimum wages may lead to greater levels of employment under perfect competition. We demonstrate this possibility in a simple generalequilibrium model with two goods produced by two factors and consumed by two representative households. Within our model, hiking a minimum wage redistributes income between heterogeneous consumers. This redistribution may create an excess demand for the laborintensive good, and hence increase employment to restore equilibrium, despite the fact that every firm becomes less labor intensive

Unemployment and Income-Distribution Effects of Economic Growth: A Minimum-Wage Analysis with Optimal Saving

Theoretically and numerically, we analyze the unemployment and income-distribution effects of economic growth, in a model with optimal saving (investment) and a minimum wage for unskilled labor. Within this three-factor model (including skilled labor), an exogenous rise in the growth rate increases unemployment if capital and unskilled labor are complements (versus substitutes), implying a trade-off between (faster) growth and (lower) unemployment. We also show how the growth rate affects the skill premium and factor shares of national income, providing little support for Piketty’s (2014) controversial thesis that capital’s share is higher when growth is slower

A Minimum-Wage Model of Unemployment and Growth: The Case of a Backward-Bending Demand Curve for Labor

We add a minimum wage and hence involuntary unemployment to a conventional two-sector model of a perfectly competitive economy with optimal saving and endogenous growth. Our resulting model highlights the possible case of a backward-bending demand curve for labor, along which a hike in the minimum wage might increase total employment. This possibility provides theoretical support for some controversial empirical studies, which challenge the textbook prediction of an inverse relationship between employment and the minimum wage. Our model also implies that a minimum-wage hike has negative implications for both the growth rate and lifetime utilit

Electrical Stimulation Modulates High γ Activity and Human Memory Performance.

Direct electrical stimulation of the brain has emerged as a powerful treatment for multiple neurological diseases, and as a potential technique to enhance human cognition. Despite its application in a range of brain disorders, it remains unclear how stimulation of discrete brain areas affects memory performance and the underlying electrophysiological activities. Here, we investigated the effect of direct electrical stimulation in four brain regions known to support declarative memory: hippocampus (HP), parahippocampal region (PH) neocortex, prefrontal cortex (PF), and lateral temporal cortex (TC). Intracranial EEG recordings with stimulation were collected from 22 patients during performance of verbal memory tasks. We found that high γ (62-118 Hz) activity induced by word presentation was modulated by electrical stimulation. This modulatory effect was greatest for trials with poor memory encoding. The high γ modulation correlated with the behavioral effect of stimulation in a given brain region: it was negative, i.e., the induced high γ activity was decreased, in the regions where stimulation decreased memory performance, and positive in the lateral TC where memory enhancement was observed. Our results suggest that the effect of electrical stimulation on high γ activity induced by word presentation may be a useful biomarker for mapping memory networks and guiding therapeutic brain stimulation