An Axiomatic Model of Social Adaptive Behavior.

I replace the assumption that an agent makes an optimal choice by an assumption that the agent executes a computational algorithm directed at finding a choice that is good at the time the choice is made. The algorithm utilizes the individual's own information, and information about choices of other members of society. It is shown that under some regularity conditions any such algorithm can be decomposed into generalized gradient dynamics, direct imitation, experimentation, and imitation of scope.BEHAVIOUR ; INFORMATION ; ECONOMIC MODELS

Incentives for Boundedly Rational Agents.

This paper develops a theoretical framework for analyzing incentive schemes under bounded rationality. It starts from a standard principal-agent model and then superimposes an assumption of boundedly rational behavior on the part of the agent. Boundedly rational behavior is modeled as an explicit optimization procedure which combines gradient dynamics with a specific form of social learning called imitation of scope.RATIONALITY ; ECONOMIC MODELS ; BEHAVIOUR

A Noisy Model of Individual Behaviour.

This paper develops a model of individual adjustment subject to mistakes. In this case when mistakes are assumed i.i.d., this process produces a probability distribution of agents decision whose evolution is determined by Fokker-Planck equation. This distribution converges to the unique, globally stable stationary distribution. In the case when choice space is one dimensional this distribution satisfies Independence of Irrelevant Alternatives (IIA) property. In multidimensional case for IIA to hold strong additional conditions on payoff function or error structure should be satisfied. The paper also considers generalization of model for autocorrelated errors in one-dimensional case.WAGES ; DISTRIBUTION ; BEHAVIOUR

Coherence and superconductivity in coupled one-dimensional chains: a case study of YBa2_{2}Cu3_{3}Oy_{y}

We report the infrared (IR) response of Cu-O chains in the high-$T_{c}$ superconductor YBa$_{2}$Cu$_{3}$O$_{y}$ over the doping range spanning $y=6.28-6.75$. We find evidence for a power law scaling at mid-IR frequencies consistent with predictions for Tomonaga-Luttinger liquid, thus supporting the notion of one-dimensional transport in the chains. We analyze the role of coupling to the CuO$_{2}$ planes in establishing metallicity and superconductivity in disordered chain fragments.Comment: 4 pages, 3 figure

Comment on ''Phase Diagram of La2−x_{2-x}Srx_xCuO4_4 Probed in the Infrared: Imprints of Charge Stripe Excitations''

Recently Lucarelli {\it et al.} have reported\cite{lucarelli} temperature-dependence of the in-plane optical reflectivity of La$_{2-x}$Sr$_x$CuO$_4$ over a wide doping range, focusing on the infrared peaks at 30 cm$^{-1}$ (for $x$=0.12), 250 cm$^{-1}$ and 510 cm$^{-1}$. They interpreted the first peak (30 cm$^{-1}$) as a signature of charge stripe ordering, while the latter two (250 cm$^{-1}$ and 510 cm$^{-1}$) are attributed to the polaronic charge excitations. However, careful readers would notice that the reported spectra are largely different from those so far measured on the same system. As we illustrate below, all these peaks are caused by an uncontrolled leakage of the c-axis reflectivity into the measured spectra.Comment: 1 page, 1 figure, accepted for publication in Phys. Rev. Lett 91 (2003

An Infrared study of the Josephson vortex state in high-Tc cuprates

We report the results of the c-axis infrared spectroscopy of La_{2-x} Sr_x CuO_4 in high magnetic field oriented parallel to the CuO_2 planes. A significant suppression of the superfluid density with magnetic field rho_s(H) is observed for both underdoped (x=0.125) and overdoped (x=0.17) samples. We show that the existing theoretical models of the Josephson vortex state fail to consistently describe the observed effects and discuss possible reasons for the discrepancies

Angle-resolved photoemission spectra in the cuprates from the d-density wave theory

Angle-resolved photoemission spectra present two challenges for the d-density wave (DDW) theory of the pseudogap state of the cuprates: (1) hole pockets near $(\pi/2,\pi/2)$ are not observed, in apparent contradiction with the assumption of translational symmetry breaking, and (2) there are no well-defined quasiparticles at the {\it antinodal} points, in contradiction with the predictions of mean-field theory of this broken symmetry state. Here, we show how these puzzles can be resolved.Comment: 4 pages, 3 eps figures, RevTex

Quasiparticle dynamics and in-plane anisotropy in YBa2Cu3OyY Ba_2 Cu_3 O_y system near onset of superconductivity

We report on an infrared study of carrier dynamics within the CuO$_{2}$ planes in heavily underdoped detwinned single crystals of YBa$_{2}$Cu$_{3}$O$_{y}$. In an effort to reveal the electronic structure near the onset of superconductivity, we investigate the strong anisotropy of the electromagnetic response due to an enhancement of the scattering rate along the a-axis. We propose that the origin of this anisotropy is related to a modulation of the electron density within the CuO$_{2}$ planes.Comment: 5 pages, 4 figure

Plasmonic Hot Spots in Triangular Tapered Graphene Microcrystals

Recently, plasmons in graphene have been observed experimentally using scattering scanning near-field optical microscopy. In this paper, we develop a simplified analytical approach to describe the behavior in triangular samples. Replacing Coulomb interaction by a short-range one reduces the problem to a Helmholtz equation, amenable to analytical treatment. We demonstrate that even with our simplifications, the system still exhibits the key features seen in the experiment.Comment: 4 pages, 3 figure