7,395 research outputs found
Does Opportunistic Fraud in Automobile theft Insurance Fluctuate with the Business Cycle ?
We analyze the empirical relationship between opportunistic fraud and business cycle. We find that residual opportunistic fraud exists both in the contract with replacement cost endorsement and the contract with no-deductible endorsement in the Taiwan automobile theft insurance market. These results are consistent with previous literature on the relationship between fraud activity and insurance contracting. We also show that the severity of opportunistic fraud fluctuates in the opposite direction to the business cycle. Opportunistic fraud is stimulated during periods of recession and mitigated during periods of expansion.Opportunistic fraud, replacement cost endorsement, no-deductible endorsement, automobile theft insurance, business cycle
An experimental study of wine consumers’ willingness to pay for environmental characteristics
The reduction of pesticides use is becoming a priority for the public authorities in many countries. We conducted an experiment with wine consumers to see whether end-consumers value the dissemination of information about environmentally-friendly production practices. The experiment was devised to (i) evaluate whether there is a premium for environmentally-friendly wines, (ii) determine whether or not consumers are sensitive to label owners who implement and guarantee the environmental actions, (iii) and assess the impact of public messages about the consequences of pesticide use. Some 139 participants were divided randomly into two groups. One group had no specific information about the current state of pesticide use in farming. The other group was given information about pesticide use in farming before making their valuations. Becker-DeGroot-Marshak mechanisms revealed that (i) the environmental signal is valued differently depending on who conveyed the information, and that (ii)dissemination of information about the environmental repercussions of farming methods does not significantly affect willingness-to-pay.Willingness to pay, Wine, Effect of information, Experimental economics, Environment, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,
Theory of light-enhanced phonon-mediated superconductivity
We investigate the dynamics of a phonon-mediated superconductor driven out of
equilibrium. The electronic hopping amplitude is ramped down in time, resulting
in an increased electronic density of states. The dynamics of the coupled
electron-phonon model is investigated by solving Migdal-Eliashberg equations
for the double-time Keldysh Green's functions. The increase of the density of
states near the Fermi level leads to an enhancement of superconductivity when
the system thermalizes to the new state at the same temperature. We provide a
time- and momentum-resolved view on this thermalization process, and show that
it involves fast processes associated with single-particle scattering and much
slower dynamics associated with the superconducting order parameter. The
importance of electron-phonon coupling for the rapid enhancement and the
efficient thermalization of superconductivity is demonstrated, and the results
are compared to a BCS time-dependent mean-field approximation.Comment: 12 pages, 8 figure
Dynamic simulation of hydrodynamically interacting suspensions
A general method for computing the hydrodynamic interactions among an infinite suspension of particles, under the condition of vanishingly small particle Reynolds number, is presented. The method follows the procedure developed by O'Brien (1979) for constructing absolutely convergent expressions for particle interactions. For use in dynamic simulation, the convergence of these expressions is accelerated by application of the Ewald summation technique. The resulting hydrodynamic mobility and/or resistance matrices correctly include all far-field non-convergent interactions. Near-field lubrication interactions are incorporated into the resistance matrix using the technique developed by Durlofsky, Brady & Bossis (1987). The method is rigorous, accurate and computationally efficient, and forms the basis of the Stokesian-dynamics simulation method. The method is completely general and allows such diverse suspension problems as self-diffusion, sedimentation, rheology and flow in porous media to be treated within the same formulation for any microstructural arrangement of particles. The accuracy of the Stokesian-dynamics method is illustrated by comparing with the known exact results for spatially periodic suspensions
Exact Diagonalization Dynamical Mean Field Theory for Multi-Band Materials: Effect of Coulomb correlations on the Fermi surface of Na_0.3CoO_2
Dynamical mean field theory combined with finite-temperature exact
diagonalization is shown to be a suitable method to study local Coulomb
correlations in realistic multi-band materials. By making use of the sparseness
of the impurity Hamiltonian, exact eigenstates can be evaluated for
significantly larger clusters than in schemes based on full diagonalization.
Since finite-size effects are greatly reduced this approach allows the study of
three-band systems down to very low temperatures, for strong local Coulomb
interactions and full Hund exchange. It is also shown that exact
diagonalization yields smooth subband quasi-particle spectra and self-energies
at real frequencies. As a first application the correlation induced charge
transfer between t2g bands in Na_0.3CoO_2 is investigated. For both Hund and
Ising exchange the small eg' Fermi surface hole pockets are found to be
slightly enlarged compared to the non-interacting limit, in agreement with
previous Quantum Monte Carlo dynamical mean field calculations for Ising
exchange, but in conflict with photoemission data.Comment: 9 pages, 7 figure
Superconductivity in the Two-Band Hubbard Model in Infinite Dimensions
We study a two-band Hubbard model in the limit of infinite dimensions, using
a combination of analytical methods and Monte-Carlo techniques. The normal
state is found to display various metal to insulators transitions as a function
of doping and interaction strength. We derive self-consistent equations for the
local Green's functions in the presence of superconducting long-range order,
and extend previous algorithms to this case. We present direct numerical
evidence that in a specific range of parameter space, the normal state is
unstable against a superconducting state characterized by a strongly frequency
dependent order-parameter.Comment: 12 pages (14 figures not included, available upon request), Latex,
LPTENS Preprint 93/1
Chemical weathering of the volcanic soils of Isla Santa Cruz (Galápagos Islands, Ecuador)
We present a study on weathering of volcanic soils using 43 profiles (131 horizons) sampled in Santa Cruz Island (Galapagos Islands). Several weathering indices, based on chemical composition, are used. Since the geological material is highly homogeneous the intensity of weathering is mostly related to climatic conditions controlled by topography. There is a gradient of increasing weathering from the arid conditions predominant in the coast to elevations of 400-500 m a.s.l. where much more humid conditions prevail
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