OPTION VALUE OF HARVESTING: THEORY AND EVIDENCE

Real options analysis shows that fishery harvesting becomes more conservative, and catch efficiency is raised, when exploitation is subject to irreversibility, uncertainty, and delay for a cooperative profit-maximizing fleet. With Rock Lobster catch and effort data from Fisheries Victoria of the Department of Natural Resources and Environment in Australia, the options-augmented surplus-yield model is tested and compared with the performance of its conventional profit-maximizing and biological maximum-sustainable-yield counterparts.Resource /Energy Economics and Policy,

A Reply to “Option Value of Harvesting†Revisited (The Comment)

Li’s results (1998) are correct and robust. The Comment offers an interesting perspective from real-options theory, albeit misguided--from a resource-economics point of view. In particular, the lack of sensitivity in the optimal harvest trigger to biomass uncertainty is questionable. This reply begins with a general overview of resource-economic principles and the role of real options in them. A specific reply to each point raised in The Comment will then be addressed.Productivity Analysis, Research Methods/ Statistical Methods,

COOPERATIVE HIGH-SEAS STRADDLING STOCK AGREEMENT AS A CHARACTERISTIC FUNCTION GAME

In the economic management of high-seas straddling fish stocks, we analyze the negotiation of a cooperative agreement by way of a characteristic function game (c-game). The benefits of a grand coalition may be distributed differently, depending on the negotiating members' harvesting efficiency and the concept of fairness chosen during negotiation. In the paper, we examine three such concepts: nucleolus, Shapley-value, and egalitarian. In general, a fleet's harvesting efficiency will determine the contribution it makes to any subcoalitions, or the grand coalition, in which it is the last to join. Analysis shows that the imputation to each member under each fairness concept differs according to whether the maximum, or the average, contribution is used, or whether the contribution can be regarded as bargaining power at all. By making certain assumptions regarding fleet efficiency, we calculated the exact imputation under each fairness concept and compared the change from one to another. Conclusions are then drawn with suggested further research.Institutional and Behavioral Economics, Resource /Energy Economics and Policy,

Numerical study of scars in a chaotic billiard

We study numerically the scaling properties of scars in stadium billiard. Using the semiclassical criterion, we have searched systematically the scars of the same type through a very wide range, from ground state to as high as the 1 millionth state. We have analyzed the integrated probability density along the periodic orbit. The numerical results confirm that the average intensity of certain types of scars is independent of $\hbar$ rather than scales with $\sqrt{\hbar}$. Our findings confirm the theoretical predictions of Robnik (1989).Comment: 7 pages in Revtex 3.1, 5 PS figures available upon request. To appear in Phys. Rev. E, Vol. 55, No. 5, 199

On String Tunneling in Power Law Inflationary Universes

We consider the evolution of circular string loops in power law expanding universes represented by a spatially flat Friedman-Robertson-Walker metric with scale factor $a(t)\propto t^p$ where $t$ is the cosmic time and $p\geq 0$. Our main result is the existence of a "magic" power $p_m=3+2\sqrt{2}$. In spacetimes with $p<p_m$ a circular string expands either forever or to a maximal radius and then contracts until it collapses into a point (black hole). For $p>p_m$, however, we find additional types of solutions. They include configurations which contract from a positive initial radius to a minimal one and then expand forever. Their existence we interpret as an indication for the presence of a finite potential barrier. Equivalently the new solutions signal string nucleation and tunneling, phenomena recently shown to occur in de Sitter space.Comment: Latex, 9 pages + 4 figures (not included), NBI-HE-93-5

The Effects of Disorder on the ν=1\nu=1 Quantum Hall State

A disorder-averaged Hartree-Fock treatment is used to compute the density of single particle states for quantum Hall systems at filling factor $\nu=1$. It is found that transport and spin polarization experiments can be simultaneously explained by a model of mostly short-range effective disorder. The slope of the transport gap (due to quasiparticles) in parallel field emerges as a result of the interplay between disorder-induced broadening and exchange, and has implications for skyrmion localization.Comment: 4 pages, 3 eps figure

Solid--on--Solid Model for Adsorption on Self--Affine Substrate: A Transfer Matrix Approach

We study a $d=2$ discrete solid--on--solid model of complete wetting of a rough substrate with random self--affine boundary, having roughness exponent $\zeta_s$. A suitable transfer matrix approach allows to discuss adsorption isotherms, as well as geometrical and thermal fluctuations of the interface. For $\zeta_s\leq 1/2$ the same wetting exponent $\psi=1/3$ as for flat substrate is obtained for the dependence of the coverage, $\theta$, on the chemical potential, $h$ ($\theta\sim h^{-\psi}$ for $h\to 0$). The expected existence of a zero temperature fixed point, leading to $\psi=\zeta_s /(2-\zeta_s)$ for $\zeta_s>1/2$, is verified numerically in spite of an unexpected, very slow convergence to asymptotics.Comment: Standard TeX, 13 pages. 5 PostScript figures available on request. Preprint UDPHIR 94/04/G

Density of states and magnetoconductance of disordered Au point contacts

We report the first low temperature magnetotransport measurements on electrochemically fabricated atomic scale gold nanojunctions. As $T \to 0$, the junctions exhibit nonperturbatively large zero bias anomalies (ZBAs) in their differential conductance. We consider several explanations and find that the ZBAs are consistent with a reduced local density of states (LDOS) in the disordered metal. We suggest that this is a result of Coulomb interactions in a granular metal with moderate intergrain coupling. Magnetoconductance of atomic scale junctions also differs significantly from that of less geometrically constrained devices, and supports this explanation.Comment: 5 pages, 5 figures. Accepted to PRB as Brief Repor

The evolution of cosmic string loops in Kerr-de Sitter spacetimes

The equation of cosmic string loops in Kerr-de Sitter spacetimes is derived. Having solved the equation numerically, we find that the loops can expand and exist except for too small ones.Comment: 8 page

Compact spherical neutron polarimeter using high-T-c YBCO films

We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-Tc superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device’s field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 μm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field