19,262 research outputs found
Do Farmers Choose the Number of Landlords as A Way to Deal with Risks? Evidence from U.S. Household Level Data
Replaced with revised version of poster 07/21/11.Risk and Uncertainty,
Reheating mechanism of Curvaton with Nonminimal Derivative Coupling to Gravity
In this paper, we continue our study on the curvaton model with nonminimal
derivative coupling (NDC) to Einstein gravity proposed in our previous work,
focusing on the reheating mechanism. We found that according to whether the
curvaton has dominated the background after the end of inflation, it will have
two different behaviors of evolution, which should be the general property of
curvaton with nonminimal couplings. This will cause diffferent rates of
particle creation, which goes on via the parametric resonance process. The
reheating temperature is estimated for both cases in which reheating completes
before and after curvaton domination, and the constraints are quite loose
compared to that of overproduction of gravitino. Finally we investigated the
evolution of curvature perturbation during reheating. We have shown both
analytically and numerically that the curvature perturbation will not blow up
during the resonance process.Comment: 10 pages, 8 figures. corrections are made to match the published
versio
Relationships Between Generalized Bernoulli Numbers and Polynomials and Generalized Euler Numbers and Polynomials
In this paper, concepts of the generalized Bernoulli and Euler numbers and polynomials are introduced, and some relationships between them are established
Self-Organized Vortices of Circling Self-Propelled Particles and Curved Active Flagella
Self-propelled point-like particles move along circular trajectories when
their translocation velocity is constant and the angular velocity related to
their orientation vector is also constant. We investigate the collective
behavior of ensembles of such circle swimmers by Brownian dynamics simulations.
If the particles interact via a "velocity-trajectory coordination" rule within
neighboring particles, a self-organized vortex pattern emerges. This vortex
pattern is characterized by its particle-density correlation function ,
the density correlation function of trajectory centers, and an order
parameter representing the degree of the aggregation of the particles.
Here, we systematically vary the system parameters, such as the particle
density and the interaction range, in order to reveal the transition of the
system from a light-vortex-dominated to heavy-vortex-dominated state, where
vortices contain mainly a single and many self-propelled particles,
respectively. We also study a semi-dilute solution of curved,
sinusoidal-beating flagella, as an example of circling self-propelled particles
with explicit propulsion mechanism and excluded-volume interactions. Our
simulation results are compared with previous experimental results for the
vortices in sea-urchin sperm solutions near a wall. The properties of the
vortices in simulations and experiments are found to agree quantitatively.Comment: 14 pages, 15 figure
The Implications of Binding Farm Program Payment Limits Associated with Income Means Testing
Replaced with revised version of poster 07/20/11.Agricultural and Food Policy,
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