A Note on Quantum Field Theories with a Minimal Length Scale

The aim of this note is to address the low energy limit of quantum field theories with a minimal length scale. The essential feature of these models is that the minimal length acts as a regulator in the asymptotic high energy limit which is incorporated through an infinite series of higher order derivatives. If one investigates a perturbative expansion in inverse powers of the Planck mass, one generically obtains extra poles in the propagator, and instabilities connected with the higher order derivative Lagrangian, that are however artifacts of truncating the series

Is my ODE a Painleve equation in disguise?

Painleve equations belong to the class y'' + a_1 {y'}^3 + 3 a_2 {y'}^2 + 3 a_3 y' + a_4 = 0, where a_i=a_i(x,y). This class of equations is invariant under the general point transformation x=Phi(X,Y), y=Psi(X,Y) and it is therefore very difficult to find out whether two equations in this class are related. We describe R. Liouville's theory of invariants that can be used to construct invariant characteristic expressions (syzygies), and in particular present such a characterization for Painleve equations I-IV.Comment: 8 pages. Based on talks presented at NEEDS 2000, Gokova, Turkey, 29 June - 7 July, 2000, and at the AMS-HKMS joint meeting 13-16 December, 2000. Submitted to J. Nonlin. Math. Phy

An Integral Spectral Representation of the Propagator for the Wave Equation in the Kerr Geometry

We consider the scalar wave equation in the Kerr geometry for Cauchy data which is smooth and compactly supported outside the event horizon. We derive an integral representation which expresses the solution as a superposition of solutions of the radial and angular ODEs which arise in the separation of variables. In particular, we prove completeness of the solutions of the separated ODEs. This integral representation is a suitable starting point for a detailed analysis of the long-time dynamics of scalar waves in the Kerr geometry.Comment: 41 pages, 4 figures, minor correction

Ambipolar Nernst effect in NbSe2_2

The first study of Nernst effect in NbSe$_2$ reveals a large quasi-particle contribution with a magnitude comparable and a sign opposite to the vortex signal. Comparing the effect of the Charge Density Wave(CDW) transition on Hall and Nernst coefficients, we argue that this large Nernst signal originates from the thermally-induced counterflow of electrons and holes and indicates a drastic change in the electron scattering rate in the CDW state. The results provide new input for the debate on the origin of the anomalous Nernst signal in high-T$_c$ cuprates.Comment: 5 pages including 4 figure

Low activity microstates during sleep

Study Objectives: To better understand the distinct activity patterns of the brain during sleep, we observed and investigated periods of diminished oscillatory and population spiking activity lasting for seconds during non-rapid eye movement (non-REM) sleep, which we call “LOW” activity sleep. Methods: We analyzed spiking and local field potential (LFP) activity of hippocampal CA1 region alongside neocortical electroencephalogram (EEG) and electromyogram (EMG) in 19 sessions from four male Long-Evans rats (260–360 g) during natural wake/sleep across the 24-hr cycle as well as data from other brain regions obtained from http://crcns.org. Results: LOW states lasted longer than OFF/DOWN states and were distinguished by a subset of “LOW-active” cells. LOW activity sleep was preceded and followed by increased sharp-wave ripple activity. We also observed decreased slow-wave activity and sleep spindles in the hippocampal LFP and neocortical EEG upon LOW onset, with a partial rebound immediately after LOW. LOW states demonstrated activity patterns consistent with sleep but frequently transitioned into microarousals and showed EMG and LFP differences from small-amplitude irregular activity during quiet waking. Their likelihood decreased within individual non-REM epochs yet increased over the course of sleep. By analyzing data from the entorhinal cortex of rats,1 as well as the hippocampus, the medial prefrontal cortex, the postsubiculum, and the anterior thalamus of mice,2 obtained from http://crcns.org, we confirmed that LOW states corresponded to markedly diminished activity simultaneously in all of these regions. Conclusions: We propose that LOW states are an important microstate within non-REM sleep that provide respite from high-activity sleep and may serve a restorative function

Matching Morphology and Diet in the Disc-Winged Bat Thyroptera tricolor (Chiroptera)

The dietary niche and morphological adaptations of a species should be highly correlated. However, conflicting selective pressures may make predictions about diet difficult without additional knowledge of a species' life history. We tested the reliability of predicting a bat's diet from its wing morphology using data for Spix's disk-winged bat (Thyroptera tricolor). The species had been predicted to fall within either the aerial hawking or gleaning foraging group. We compared the results of a theoretical (canonical discriminant function analysis of morphology) and an applied (analysis of droppings) method of diet determination. Our results place T. tricolor in the gleaning functional group with a 77% probability according to morphology. Correspondingly, a large proportion of the diverse diet consisted of nonflying prey, such as spiders, insect larvae, and other silent prey, which should be difficult to detect using echolocation. Although some flying prey were taken, it is clear that T. tricolor regularly gleans prey from surfaces, indicating that for this species, morphology is a useful indicator of diet. However, the breadth of the diet; the high proportion of jumping spiders, leafhoppers, and insect larvae; and the extremely small size of prey were unique features of the diet that could not be predicted from morphology alone. Thus, although comparative statistical methods and the analysis of wing morphology may be helpful to predict the general ecological niche, only detailed investigation of the life history may yield the detail needed for understanding the link between morphology and ecology of individual specie

The Effect of Economies of Scope on Iranian Banking Sector Structure: An Application of Multi-Product Function and Multi-Level Effect Approaches

This paper investigates, using a multi-product paradigm, the market structure of the Iranian banking sector to evaluate the role of scale. In so doing, we checked for economies of scope by multi-product cost function as well as the impact of potential economies on the banking sector structure including 18 banks during the period 2008–2014. The changes in Panzar-Rosse H-Statistic as a result of the variety in products reflect changes in the monopolistic power. The results show that an increase in the variety of offered products increases banks’ monopolistic power.JEL Codes - L1; G21; F3