Entanglement scaling and spatial correlations of the transverse field Ising model with perturbations

We study numerically the entanglement entropy and spatial correlations of the one dimensional transverse field Ising model with three different perturbations. First, we focus on the out of equilibrium, steady state with an energy current passing through the system. By employing a variety of matrix-product state based methods, we confirm the phase diagram and compute the entanglement entropy. Second, we consider a small perturbation that takes the system away from integrability and calculate the correlations, the central charge and the entanglement entropy. Third, we consider periodically weakened bonds, exploring the phase diagram and entanglement properties first in the situation when the weak and strong bonds alternate (period two-bonds) and then the general situation of a period of n bonds. In the latter case we find a critical weak bond that scales with the transverse field as $J'_c/J$ = $(h/J)^n$, where $J$ is the strength of the strong bond, $J'$ of the weak bond and $h$ the transverse field. We explicitly show that the energy current is not a conserved quantity in this case.Comment: 9 pages, 12 figures, version accepted in PR

Dysfunctional Non-Market Institutions and the Market

There is a widespread belief that when significant market failure occurs, there are strong incentives for non-market institutions to develop which go at least part of the way to remedying the deficiency. We demonstrate that this functionalist position is not in general valid. In particular, we examine a situation where insurance is characterized by moral hazard. We show that when market insurance is provided, supplementary mutual assistance between family and friends (unobservable to market insurers) -- a form of non-market institution -- will occur and may be harmful. This example suggests that non-market institutions can arise spontaneously even though they are dysfunctional.

The Basic Analytics of Moral Hazard

This paper develops the basic analytics of moral hazard, for the two-outcome case where either a fixed damage accident occurs or it does not. The analysis focuses on the relationship between the insurance premium paid and the insurance benefits received in the event of an accident, and is conducted in benefit-premium space. The central message of the paper is that even when the underlying functions, the expected utility function and the function relating the accident probability to accident-prevention effort, are extremely well-behaved, the indifference curves and feasibility set (the set of insurance contracts which at least break even) are not-indifference curves need not be convex and feasibility sets never are; price-and income- consumption lines may be discontinuous; and effort is not in general a monotonic or continuous function of the parameters of the insurance policies provided. Part I of this paper establishes these results, while Part II discusses sane of their implications. The bad behavior of indifference curves and the feasibility set profoundly affects the nature and existence of a competitive equilibrium. We illustrate this, though we do not provide a thorough analysis. We also show that our canonical model of an insurance market with moral hazard can be reinterpreted to provide a model of loans with bankruptcy, or of work incentives.

Randomization with Asymmetric Information

It is by now well-known that, in the presence of moral hazard or adverse selection, randomization of insurance premia and benefits may be Pareto efficient. This paper: i) provides a typology of the various forms that randomization may take; ii) derives necessary and/or sufficient conditions for the desirability of these various forms of randomization; iii) obtains some simple characterization theorems of the efficient random policies; iv) gives some intuition behind the results; and v) considers why randomization appears to occur less often in practice than the theory suggests it should.

Moral Hazard and Optimal Commodity Taxation

The central result of this paper is that when moral hazard ispresent,competitive equilibrium is almost always (constrained) inefficient. Moral hazard causes shadow prices to deviate from market prices. To remedy this market failure, the government could introduce differential commodity taxation. Moral hazard causes people to take too little care to prevent accidents. The corresponding dead-weight loss can be reduced by subsidizing (taxing) those goods the consumption of which encourages (discourages) accident avoidance.At the (constrained) optimum, the sum of the deadweight losses as-sociated with moral hazard, on the one hand, and differential commodity taxation, on the other, is minimized.

The Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) of Washington State

Froeschner (1988) recorded 23 species of stink bugs (Hemiptera: Heteroptera: Pentatomidae) from Washington State. Based on material primarily housed in the M. T. James Entomological Collection at Washington State University, the number of species is increased to 51. Three species recorded by Froeschner (1988) were not found in our collections: Apateticus crocatus (Uhler), Chlorochroa rossiana Buxton and Thomas, and Tepa rugulosa (Say). Species recorded from Washington State for the first time are: Apoecilus bracteatus (Fitch), Perillus bioculatus (Fabricius), Podisus maculiventris (Say), P. pallens (Stål), P. placidus Uhler, P. serieventris Uhler, Zicrona caerulea (Linnaeus), Halyomorpha halys (Stål), Brochymena quadripustulata (Fabricius), B. sulcata Van Duzee, Acrosternum hilare (Say), Aelia americana Dallas, Banasa euchlora Stål, B. tumidifrons Thomas and Yonke, Chlorochroa congrua Uhler, Coenus delius (Say), Cosmopepla uhleri Montandon, Dendrocoris pini Montandon, Euschistus servus (Say), E. tristigmus (Say), E. variolarius (Palisot), Holcostethus limbolarius (Say), Neottiglossa sulcifrons Stål, N. undata (Say), Prionosoma podopioides (Uhler), Tepa yerma (Rolston), Trichopepla grossa (Van Duzee), and Amaurochrous vanduzeei Barber and Sailer

Market Structure, Organizational Structure, and R&D Diversity

We examine the effects of market structure and the internal organization of firms on equilibrium R&D projects. We compare a monopolist's choice of R&D portfolio to that of a welfare maximizer. We next show that Sah and Stiglitz's finding that the market portfolio of R&D is independent of the number of firms under Bertrand competition extends to neither Cournot oligopoly nor a cartel. We also show that the ability of firms to pre-empt R&D by rivals along particular research paths can lead to socially excessive R&D diversification. Lastly, using Sah and Stiglitz's definition of hierarchy, we establish conditions under which larger hierarchies invest in smaller portfolios.

Ionization Sources and Physical Conditions in the Diffuse Ionized Gas Halos of Four Edge-On Galaxies

Deep long-slit spectra of the diffuse ionized gas halos of the edge-on spiral galaxies NGC 4302 and UGC 10288 are presented. These data, along with previously presented data for NGC 5775 and NGC 891, are used to address the issue of how DIG halos are energized. Composite photo-ionization/shock models are generally better at explaining runs of line ratios in these galaxies than photo-ionization models alone. Models of line ratios in NGC 5775 require a greater contribution from shocks for filamentary regions than for non-filamentary regions to explain the run of [OIII]/Halpha. In either case, the [SII]/[NII] ratio is not well fit by the models. Composite models for UGC 10288 are successful at reproducing the run of [SII]/[NII] for all but the the highest values of [NII]/Halpha; however, the run of [OIII]/Halpha vs. [NII]/Halpha does not show any discernible trend, making it difficult to determine whether or not shocks make a contribution. We also examine whether the data can be explained simply by an increase in temperature with z in a pure photo-ionization model. Runs of [SII]/Halpha, [NII]/Halpha, and [SII]/[NII] in each of the four galaxies are consistent with such an increase. However, the runs of [OIII]/Halpha vs. z in NGC 5775 and UGC 10288 require unusually high ionization fractions of O^{++} that can not be explained without invoking a secondary ionization source or at the very least a much higher temperature for the [OIII]-emitting component than for the [SII]- and [NII]-emitting component. An increase in temperature with z is generally more successful at explaining the [OIII]/Halpha run in NGC 891.Comment: 42 pages in aaspp4.sty format. This includes the 19 figures. Reference added. Accepted for publication in Ap

Barriers to recovery and recommendations for change: the Pennsylvania Consensus Conference on psychiatry\u27s role.

OBJECTIVE: Recovery has emerged over the past decade as a dominant theme in public mental health care. METHODS: The 2006 Pennsylvania Consensus Conference brought together 24 community psychiatrists to explore the barriers they experienced in promoting recovery and their recommendations for change. RESULTS: Twelve barriers were identified and classified into one of three categories: psychiatry knowledge, roles, and training; the need to transform public mental health systems and services; and environmental barriers to opportunity. Participants made 22 recommendations to address these barriers through changes in policies, programs, and psychiatric knowledge and practice. CONCLUSIONS: The recommendations identify areas for change that can be accomplished through individual psychiatrist action and organized group efforts