Agri-environmental program compliance under heterogeneous conditions

Heterogeneity of agricultural landscapes may necessitate the use of spatially targeted instrument combinations to implement the social optimum. But compliance with these policies may require costly enforcement. This paper examines the design of agri-environmental policies featuring two of the most commonly used instruments, reductions in fertilizer application rates and installation of riparian buffers. While compliance with buffer strip requirements is verifiable at negligible cost, fertilizer application is only verifiable through costly monitoring. We derive optimal subsidies for fertilizer reduction and buffer strip set-asides and enforcement strategies for the cases of low and excessive monitoring costs. An empirical simulation model suggests that enforceable policies can come close to replicating socially optimal crop production, nitrogen runoff, and overall welfare without requiring increases in overall subsidy expenditures, at least under conditions characteristic of Scandinavia.nutrient runoff, monitoring, enforcement, Environmental Economics and Policy,

Agri-Environmental Program Compliance in a Heterogeneous Landscape

Heterogeneity of agricultural landscapes may necessitate the use of spatially targeted instrument combinations to implement the social optimum. But compliance with these policies may require costly enforcement. This paper examines the design of agri-environmental policies featuring two of the most commonly used instruments, reductions in fertilizer application rates and installation of riparian buffers. While compliance with buffer strip requirements is verifiable at negligible cost, fertilizer application is only verifiable through costly monitoring. We derive optimal subsidies for fertilizer reduction and buffer strip set-asides and enforcement strategies for the cases of low and excessive monitoring costs. An empirical simulation model suggests that enforceable policies can come close to replicating socially optimal crop production, nitrogen runoff, and overall welfare without requiring increases in overall subsidy expenditures, at least under conditions characteristic of Scandinavia. Sensitivity analysis suggests that these conclusions may carry over to areas with higher overall land quality as well.nutrient runoff, monitoring, enforcement, Agricultural and Food Policy, Environmental Economics and Policy, Q15, Q18, H23,

Spin of ground state baryons

We calculate the quark spin contribution to the total angular momentum of flavor octet and flavor decuplet ground state baryons using a spin-flavor symmetry based parametrization method of quantum chromodynamics. We find that third order SU(6) symmetry breaking three-quark operators are necessary to explain the experimental result Sigma_1=0.32(10). For spin 3/2 decuplet baryons we predict that the quark spin contribution is Sigma_3=3.93(22), i.e. considerably larger than their total angular momentum.Comment: 8 page

Dark halos acting as chaos controllers in asymmetric triaxial galaxy models

We study the regular or chaotic character of orbits in a 3D dynamical model, describing a triaxial galaxy surrounded by a spherical dark halo component. Our numerical experiments suggest that the percentage of chaotic orbits decreases exponentially as the mass of the dark halo increases. A linear increase of the percentage of the chaotic orbits was observed as the scale length of the halo component increases. In order to distinguish between regular and chaotic motion, we chose to use the total angular momentum Ltot of the 3D orbits as a new indicator. Comparison with other, previously used, dynamical indicators, such as the Lyapunov Characteristic Exponent or the P(f) spectral method, shows that the Ltot indicator gives very fast and reliable results for characterizing the nature of orbits in galactic dynamical models.Comment: Published in Research in Astronomy and Astrophysics (RAA) journa

Classical diffusion in double-delta-kicked particles

We investigate the classical chaotic diffusion of atoms subjected to {\em pairs} of closely spaced pulses (`kicks) from standing waves of light (the $2\delta$-KP). Recent experimental studies with cold atoms implied an underlying classical diffusion of type very different from the well-known paradigm of Hamiltonian chaos, the Standard Map. The kicks in each pair are separated by a small time interval $\epsilon \ll 1$, which together with the kick strength $K$, characterizes the transport. Phase space for the $2\delta$-KP is partitioned into momentum `cells' partially separated by momentum-trapping regions where diffusion is slow. We present here an analytical derivation of the classical diffusion for a $2\delta$-KP including all important correlations which were used to analyze the experimental data. We find a new asymptotic ($t \to \infty$) regime of `hindered' diffusion: while for the Standard Map the diffusion rate, for $K \gg 1$, $D \sim K^2/2[1- J_2(K)..]$ oscillates about the uncorrelated, rate $D_0 =K^2/2$, we find analytically, that the $2\delta$-KP can equal, but never diffuses faster than, a random walk rate. We argue this is due to the destruction of the important classical `accelerator modes' of the Standard Map. We analyze the experimental regime $0.1\lesssim K\epsilon \lesssim 1$, where quantum localisation lengths $L \sim \hbar^{-0.75}$ are affected by fractal cell boundaries. We find an approximate asymptotic diffusion rate $D\propto K^3\epsilon$, in correspondence to a $D\propto K^3$ regime in the Standard Map associated with 'golden-ratio' cantori.Comment: 14 pages, 10 figures, error in equation in appendix correcte

Regular-to-chaotic tunneling rates using a fictitious integrable system

We derive a formula predicting dynamical tunneling rates from regular states to the chaotic sea in systems with a mixed phase space. Our approach is based on the introduction of a fictitious integrable system that resembles the regular dynamics within the island. For the standard map and other kicked systems we find agreement with numerical results for all regular states in a regime where resonance-assisted tunneling is not relevant.Comment: 4 pages, 4 figure

Comparing the behavior of orbits in different 3D dynamical models for elliptical galaxies

We study the behavior of orbits in two different galactic dynamical models, describing the motion in the central parts of a triaxial elliptical galaxy with a dense nucleus. Numerical experiments show that both models display regular motion together with extended chaotic regions. A detailed investigation of the properties of motion is made for the 2D and 3D Hamiltonian systems, using a number of different dynamical parameters, such as the Poincare surface of section, the maximal Lyapunov Characteristic Exponent, the S(c) spectrum, the S(w) spectrum and the P(f) indicator. The numerical calculations suggest that the properties of motion in both potentials are very similar. Our results show that one may use different kinds of gravitational potentials in order to describe the motion in triaxial galaxies while obtaining quantitatively similar results.Comment: Published in Research in Astronomy and Astrophysics journa