General non-existence theorem for phase transitions in one-dimensional systems with short range interactions, and physical examples of such transitions

We examine critically the issue of phase transitions in one-dimensional systems with short range interactions. We begin by reviewing in detail the most famous non-existence result, namely van Hove's theorem, emphasizing its hypothesis and subsequently its limited range of applicability. To further underscore this point, we present several examples of one-dimensional short ranged models that exhibit true, thermodynamic phase transitions, with increasing level of complexity and closeness to reality. Thus having made clear the necessity for a result broader than van Hove's theorem, we set out to prove such a general non-existence theorem, widening largely the class of models known to be free of phase transitions. The theorem is presented from a rigorous mathematical point of view although examples of the framework corresponding to usual physical systems are given along the way. We close the paper with a discussion in more physical terms of the implications of this non-existence theorem.Comment: Short comment on possible generalization to wider classes of systems added; accepted for publication in Journal of Statistical Physic

Estimating a Signal In the Presence of an Unknown Background

We describe a method for fitting distributions to data which only requires knowledge of the parametric form of either the signal or the background but not both. The unknown distribution is fit using a non-parametric kernel density estimator. The method returns parameter estimates as well as errors on those estimates. Simulation studies show that these estimates are unbiased and that the errors are correct

Coupled forward-backward trajectory approach for non-equilibrium electron-ion dynamics

We introduce a simple ansatz for the wavefunction of a many-body system based on coupled forward and backward-propagating semiclassical trajectories. This method is primarily aimed at, but not limited to, treating nonequilibrium dynamics in electron-phonon systems. The time-evolution of the system is obtained from the Euler-Lagrange variational principle, and we show that this ansatz yields Ehrenfest mean field theory in the limit that the forward and backward trajectories are orthogonal, and in the limit that they coalesce. We investigate accuracy and performance of this method by simulating electronic relaxation in the spin-boson model and the Holstein model. Although this method involves only pairs of semiclassical trajectories, it shows a substantial improvement over mean field theory, capturing quantum coherence of nuclear dynamics as well as electron-nuclear correlations. This improvement is particularly evident in nonadiabatic systems, where the accuracy of this coupled trajectory method extends well beyond the perturbative electron-phonon coupling regime. This approach thus provides an attractive route forward to the ab-initio description of relaxation processes, such as thermalization, in condensed phase systems

Distributional impacts of carbon taxation and revenue recycling: a behavioural microsimulation. ESRI WP626, June 2019

Carbon taxation is a regressive policy which contributes to public opposition towards same. We employ the Exact Affine Stone Index demand system to examine the extent to which carbon taxation in Ireland reduces emissions, as well as its distributional impacts. The Engel curves for various commodity groupings are found to be non-linear, which renders the particular demand system we have chosen more suitable than other methods found in the extant literature. We find that a carbon tax increase can decrease emissions, but is indeed regressive. Recycling the revenues to households mitigates these regressive effects. A targeted allocation that directs the revenues towards less affluent households is found to reduce inequality more than flat allocation that divides the revenues equally amongst all households; however both methods are capable of mitigating the regressive effects of the tax increase

Pull Strategy: a Marketing Strategy Public Relations to Maintain Customer Loyalty

Customer loyalty is most important asset for every company. Customer loyalty gives company many benefits such as repeat purchase and recommendation to third party. This makes many companies always try figure out the ways to maintain customer loyalty. This research is held in PT. Zinkpower Batam Indo in Jl. Brigjend Katamso KM 6,2 Tanjung Uncang, Batam. This company is pioneer of galvanizing plant in Batam and proven to have high quality of galvanizing. PT. Zinkpower Batam Indo is subsidiary of Kopf Group, a mother company with the same field. This research aims to determine PT. Zinkpower Batam Indo Marketing Public Relations\u27s strategy to maintain their customer loyalty. The method used is descriptive qualitative approach. Data collection technique in this research using depth interview, participant observation & documentation. The result is Marketing Public Relations using pull strategy to main customer loyalty, such as customer satisfaction survey, complain handling, discount and one stop service. Implementation of pull strategy proved can maintain the loyalty that will explained in this research