From quasiperiodic partial synchronization to collective chaos in populations of inhibitory neurons with delay

Collective chaos is shown to emerge, via a period-doubling cascade, from quasiperiodic partial synchronization in a population of identical inhibitory neurons with delayed global coupling. This system is thoroughly investigated by means of an exact model of the macroscopic dynamics, valid in the thermodynamic limit. The collective chaotic state is reproduced numerically with a finite population, and persists in the presence of weak heterogeneities. Finally, the relationship of the model's dynamics with fast neuronal oscillations is discussed.Comment: 5 page

Collective synchronization in the presence of reactive coupling and shear diversity

We analyze the synchronization dynamics of a model obtained from the phase reduction of the mean-field complex Ginzburg-Landau equation with heterogeneity. We present exact results that uncover the role of dissipative and reactive couplings on the synchronization transition when shears and natural frequencies are independently distributed. As it occurs in the purely dissipative case, an excess of shear diversity prevents the onset of synchronization, but this does not hold true if coupling is purely reactive. In this case the synchronization threshold turns out to depend on the mean of the shear distribution, but not on all the other distribution's moments.Comment: To appear in Phys. Rev.

Barriers to innovation and subsidy effectiveness

We explore the effects of subsidies by means of a model of firms' decisions about performing R&D when some government support can be expected. We estimate it with data on about 2,000 performinga nd nonperformingS panishm anufacturingfi rms. Wec omputet he subsidies required to induce R&D spending, we detect the firms that would cease to perform R&D without subsidies, and assess the change in the privately financed effort. Results suggest that subsidies stimulate R&D and some firms would stop performing in their absence, but most actual subsidies go to firms that would have performed R&D otherwise. We find no crowding out of private funds.Publicad

Exponential localization of singular vectors in spatiotemporal chaos

In a dynamical system the singular vector (SV) indicates which perturbation will exhibit maximal growth after a time interval $\tau$. We show that in systems with spatiotemporal chaos the SV exponentially localizes in space. Under a suitable transformation, the SV can be described in terms of the Kardar-Parisi-Zhang equation with periodic noise. A scaling argument allows us to deduce a universal power law $\tau^{-\gamma}$ for the localization of the SV. Moreover the same exponent $\gamma$ characterizes the finite-$\tau$ deviation of the Lyapunov exponent in excellent agreement with simulations. Our results may help improving existing forecasting techniques.Comment: 5 page

What form of relative performance evaluation?

We study relative performance evaluation in executive compensation when executives have private information about their ability. We assume that the joint distribution of an individual firm’s profit and market movements depends on the ability of the executive that runs the firm. In the equilibrium of the executive labor market, compensation schemes exploit this fact to sort executives of di ?erent abilities. This implies that executive compensation is increasing in own performance, but may also be increasing in industry performance-a sharp departure from standard relative performance evaluation. This result provides an explanation for the scarcity of relative performance considerations in executive compensation documented by the empirical literature.Executive compensation, relative performance evaluation

Nontwist non-Hamiltonian systems

We show that the nontwist phenomena previously observed in Hamiltonian systems exist also in time-reversible non-Hamiltonian systems. In particular, we study the two standard collision/reconnection scenarios and we compute the parameter space breakup diagram of the shearless torus. Besides the Hamiltonian routes, the breakup may occur due to the onset of attractors. We study these phenomena in coupled phase oscillators and in non-area-preserving maps.Comment: 7 pages, 5 figure

"Things Japanese" by Basil H. Chamberlain: the first cultural guide to Japan?

Basil H. Chamberlain publicó en 1890 Things Japanese, un extenso libro con formato enciclopédico en el que recogía y describía rasgos culturales de Japón. El libro tuvo un gran éxito, y fue traducido por Gonzalo Jiménez de la Espada al español en la segunda década del siglo XX, si bien dicha traducción nunca vio la luz y se conservó solo parcialmente, hasta su recuperación en el año 2014. En este trabajo, analizamos “Cosas de Japón” como una primera guía cultural dirigida al turista culto de finales del siglo XIX y comienzos del XX. De forma particular, nos centramos en su título y en el concepto que articula el libro como una metáfora cognitiva sobre una cultura diferente, la japonesa: la idea de que Japón es un mundo topsy turvy, un mundo al revés. Indagamos en los orígenes de esa idea, existente ya en los tratados de Alessandro Valignano y, especialmente, de Luis Frois.In 1890, Basil H. Chamberlain published “Things Japanese”, an encyclopaedic book on Japan and its culture. The book enjoyed a formidable success and it was translated into Spanish during the second decade of the 20th century by Gonzalo Jiménez de la Espada, although that translation was never published and only survived partially, until its recovery in 2014. Here we analyse Cosas de Japón as one of the first cultural guides for the cultivated tourist of the late 19th and early 20th centuries. In particular, we focus on its title, and the central concept that articulates the book and serves as a cognitive metaphor about a different culture: the idea that Japan is a topsy turvy world, a world upside down. We investigate the origins of this idea, already present in works by Alessandro Valignano and, especially, Luis Frois

An empirical oligopoly model of a regulated market

We model a three firm oligopoly (the Spanish fertilizer industry from 1976 to 1988) which was subject to price regulation in the form of price ceilings. A theoretical and econometric model is developed in order to identify simultaneously the behaviour of the firms and the degree to which regulation constrained the price. The collusive market-sharing arrangements involving asymmetric firms, and the less collusive outcomes of Cournot and Stackelberg, together with their constrained counterparts, are considered as particular behavioural hypotheses. The estimation of an aggregated and a disaggregated version of the model, by General Method of Moments techniques, leads us to identify the regulation-constrained Stackelberg equilibrium as the most likely outcome given the observed data.Financial support from the Ministry of Education project no. PB94-0648-C02-01 is gratefully acknowledged.Publicad

Time delay in the Kuramoto model with bimodal frequency distribution

We investigate the effects of a time-delayed all-to-all coupling scheme in a large population of oscillators with natural frequencies following a bimodal distribution. The regions of parameter space corresponding to synchronized and incoherent solutions are obtained both numerically and analytically for particular frequency distributions. In particular we find that bimodality introduces a new time scale that results in a quasiperiodic disposition of the regions of incoherence.Comment: 5 pages, 4 figure