Fragility of reputation and clustering of risk-taking

Concerns about constructing and maintaining good reputations are known to reduce borrowers' excessive risk-taking. However, I find that the self-discipline induced by these concerns is fragile, and can break down without obvious changes in economic fundamentals. Furthermore, in the aggregate, breakdowns are clustered among borrowers with intermediate and good reputations, which can exacerbate an economy's weakness and contribute to a broad economic crisis. These results come from an aggregate dynamic global game analysis of reputation formation in credit markets. The selection of a unique equilibrium is accomplished by assuming that borrowers have incomplete information about economic fundamentals.Risk

Catalogue of the ectoparasitic insects of the bats of Argentina

Taxonomy and distribution of the ectoparasitic insects of bats from Argentina, are reviewed. Seventeen species of Diptera (six of Nycteribiidae and eleven of Streblidae), six species of Siphonaptera (four ofIschnopsyllidae, one of Pulicidae, and one ofStephanocircidae), and seven species of Hemiptera (Polyctenidae) are known presently for Argentina. The information was obtained by reviewing the literature and collecting in the field between 1989 and 1998. The specimens collected in the field were compared with the type material deposited at the Field Museum of Natural History (CHNM).En este primer catalogo de insectos ectoparasitos de murcielagos de la Argentina, se ofrece informacion sobre taxonomia y distribucion. Se conocen actualmente en el pais 17 especies de Diptera (seis de Nycteribiidae yonce de Streblidae), seis de Siphonaptera (cuatro de Ischnopsyllidae, una de Pulicidae y una de Stephanocircidae) y siete especies de Hemiptera (Polyctenidae). Se consulto numerosa literatura sobre los distintos grupos y se reviso abundante material obtenido en viajes de campana realizados desde 1989 a 1998, a numerosas localidades de la Argentina. Se realizaron comparaciones con material tipo del Field Museum of Natural History (CHNM)

Efficient implementation of a van der Waals density functional: Application to double-wall carbon nanotubes

We present an efficient implementation of the van der Waals density functional of Dion et al [Phys. Rev. Lett. 92, 246401 (2004)], which expresses the nonlocal correlation energy as a double spacial integral. We factorize the integration kernel and use fast Fourier transforms to evaluate the selfconsistent potential, total energy, and atomic forces, in N log(N) operations. The resulting overhead in total computational cost, over semilocal functionals, is very moderate for medium and large systems. We apply the method to calculate the binding energies and the barriers for relative translation and rotation in double-wall carbon nanotubes.Comment: 4 pages, 1 figure, 1 tabl

Larger crises, slower recoveries: the asymmetric effects of financial frictions

It is well known that movements in lending rates are asymmetric; they rise quickly and sharply, but fall slowly and gradually. Not known is the fact that the asymmetry is stronger the less developed a country's financial system is. This new fact is here documented and explained in a model with an endogenous flow of information about economic conditions. The stronger asymmetry in less developed countries stems from their greater financial system frictions, such as monitoring and bankruptcy costs, which first magnify jumps of lending rates and then delay their recoveries by restricting the generation of information after the crisis. A quantitative exploration of the model shows the data are consistent with this explanation.Financial crises ; Developing countries

Exploring associations between micro-level models of innovation diffusion and emerging macro-level adoption patterns

A micro-level agent-based model of innovation diffusion was developed that explicitly combines (a) an individual's perception of the advantages or relative utility derived from adoption, and (b) social influence from members of the individual's social network. The micro-model was used to simulate macro-level diffusion patterns emerging from different configurations of micro-model parameters. Micro-level simulation results matched very closely the adoption patterns predicted by the widely-used Bass macro-level model (Bass, 1969). For a portion of the domain, results from micro-simulations were consistent with aggregate-level adoption patterns reported in the literature. Induced Bass macro-level parameters and responded to changes in micro-parameters: (1) increased with the number of innovators and with the rate at which innovators are introduced; (2) increased with the probability of rewiring in small-world networks, as the characteristic path length decreases; and (3) an increase in the overall perceived utility of an innovation caused a corresponding increase in induced and values. Understanding micro to macro linkages can inform the design and assessment of marketing interventions on micro-variables - or processes related to them - to enhance adoption of future products or technologies.Comment: 20 pages, 4 figures and a table of supplementary data. Accepted for publicatio

HIPPARCOS Astrometric Orbit and Evolutionary Status of HR 6046

The previously known, 6-yr spectroscopic binary HR 6046 has been speculated in the past to contain a compact object as the secondary. A recent study has re-determined the orbit with great accuracy, and shown that the companion is an evolved but otherwise normal star of nearly identical mass as the primary, which is also a giant. The binary motion was detected by the Hipparcos mission but was not properly accounted for in the published astrometric solution. Here we use the Hipparcos intermediate data in combination with the spectroscopic results to revise that solution and establish the orbital inclination angle for the first time, and with it the absolute masses M(A) = 1.38 [-0.03,+0.09] M(Sun) and M(B) = 1.36 [-0.02,+0.07] M(Sun). Aided by other constraints, we investigate the evolutionary status and confirm that the primary star is approaching the tip of the red-giant branch, while the secondary is beginning its first ascent.Comment: To appear in The Astronomical Journal. 8 pages including tables and figures, in emulateapj forma

Approximate Bayesian Computation by Subset Simulation

A new Approximate Bayesian Computation (ABC) algorithm for Bayesian updating of model parameters is proposed in this paper, which combines the ABC principles with the technique of Subset Simulation for efficient rare-event simulation, first developed in S.K. Au and J.L. Beck [1]. It has been named ABC- SubSim. The idea is to choose the nested decreasing sequence of regions in Subset Simulation as the regions that correspond to increasingly closer approximations of the actual data vector in observation space. The efficiency of the algorithm is demonstrated in two examples that illustrate some of the challenges faced in real-world applications of ABC. We show that the proposed algorithm outperforms other recent sequential ABC algorithms in terms of computational efficiency while achieving the same, or better, measure of ac- curacy in the posterior distribution. We also show that ABC-SubSim readily provides an estimate of the evidence (marginal likelihood) for posterior model class assessment, as a by-product

The pressure confined wind of the massive and compact superstar cluster M82-A1

The observed parameters of the young superstar cluster M82-A1 and its associated compact HII region are here shown to indicate a low heating efficiency or immediate loss, through radiative cooling, of a large fraction of the energy inserted by stellar winds and supernovae during the early evolution of the cluster. This implies a bimodal hydrodynamic solution which leads to a reduced mass deposition rate into the ISM, with a much reduced outflow velocity. Furthermore, to match the observed parameters of the HII region associated to M82-A1, the resultant star cluster wind is here shown to ought to be confined by a high pressure interstellar medium. The cluster wind parameters, as well as the location of the reverse shock, its cooling length and the radius of the standing outer HII region are derived analytically. All of these properties are then confirmed with a semi-analytical integration of the flow equations, which provides us also with the run of the hydrodynamic variables as a function of radius. The impact of the results is discussed and extended to other massive and young superstar clusters surrounded by a compact HII region.Comment: 19 pages, 4 figures, accepted for publication in Ap

Critical Theory of Two-Dimensional Mott Transition: Integrability and Hilbert Space Mapping

We reconsider the Mott transition in the context of a two-dimensional fermion model with density-density coupling. We exhibit a Hilbert space mapping between the original model and the Double Lattice Chern-Simons theory at the critical point by use of the representation theory of the q-oscillator and Weyl algebras. The transition is further characterized by the ground state modification. The explicit mapping provides a new tool to further probe and test the detailed physical properties of the fermionic lattice model considered here and to enhance our understanding of the Mott transition(s)

Pseudo-Newtonian planar circular restricted 3-body problem

We study the dynamics of the planar circular restricted three-body problem in the context of a pseudo-Newtonian approximation. By using the Fodor-Hoenselaers-Perj\'es procedure, we perform an expansion in the mass potential of a static massive spherical source up to the first non-Newtonian term, giving place to a gravitational potential that includes first-order general relativistic effects. With this result, we model a system composed by two pseudo-Newtonian primaries describing circular orbits around their common center of mass, and a test particle orbiting the system in the equatorial plane. The dynamics of the new system of equations is studied in terms of the Poincar\'e section method and the Lyapunov exponents, where the introduction of a new parameter $\epsilon$, allows us to observe the transition from the Newtonian to the pseudo-Newtonian regime. We show that when the Jacobian constant is fixed, a chaotic orbit in the Newtonian regime can be either chaotic or regular in the pseudo-Newtonian approach. As a general result, we find that most of the pseudo-Newtonian configurations are less stable than their Newtonian equivalent.Comment: 11 pages, 2 figures. Accepted for publication in Physics Letters A, In Pres