37,944 research outputs found
Cosmological perturbations in Horava-Lifshitz theory without detailed balance
In the Horava-Lifshitz theory of quantum gravity, two conditions -- detailed
balance and projectability -- are usually assumed. The breaking of
projectability simplifies the theory, but it leads to serious problems with the
theory. The breaking of detailed balance leads to a more complicated form of
the theory, but it appears to resolve some of the problems. Sotiriou, Visser
and Weinfurtner formulated the most general theory of Horava-Lifshitz type
without detailed balance. We compute the linear scalar perturbations of the FRW
model in this form of HL theory. We show that the higher-order curvature terms
in the action lead to a gravitational effective anisotropic stress on small
scales. Specializing to a Minkowski background, we study the spin-0 scalar mode
of the graviton, using a gauge-invariant analysis, and find that it is stable
in both the infrared and ultraviolet regimes for . However,
in this parameter range the scalar mode is a ghost.Comment: Some typos were corrected. Verison appeared in Phys. Rev. D81, 024009
(2010
Decomposability for stable processes
We characterize all possible independent symmetric alpha-stable (SaS)
components of an SaS process, 0<alpha<2. In particular, we focus on stationary
SaS processes and their independent stationary SaS components. We also develop
a parallel characterization theory for max-stable processes.Comment: Major revision. Section 4 of previous version removed due to a
mistake in the proof. Remarks 3.2 and 3.3 adde
Efficiency Costs of Subsidy Rules for Crop Insurance
Participation in federal crop insurance programs has been encouraged through premium subsidies. The current subsidy depends on contract features as well as coverage levels. This type of subsidy rule causes farmers to choose contract designs and coverages that are not efficient for managing risk, in order to capture subsidy. Farmers are found to be as well off with a flat subsidy that is up to 25% less than the value of the current regressive proportional subsidy.crop insurance, futures, risk management, subsidy, Risk and Uncertainty,
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