Leadership and self-enforcing international environmental agreements with non-negative emissions

For the widely-used linear-quadratic model of stable IEAs the key results are: (i) if the members of the IEA act in a Cournot fashion with respect to non-signatories, a stable IEA has no more than 2 signatories; (ii) if the signatories act as Stackelberg leaders, a stable IEA can have any number of signatories. These results were derived using numerical simulations and ignored the non-negativity constraint on emissions. Recent papers using analytical approaches and explicitly recognising the non-negativity constraint have suggested that with Stackelberg leadership a stable IEA has at most four signatories. Such papers have introduced non-negativity constraints by restricting parameter values to ensure interior solutions for emissions, which restricts the number of signatories. We use the more appropriate approach of directly imposing the non-negativity constraint on emissions, recognising that for some parameter values this will entail corner solutions, and show, analytically, that the key results from the literature go through

Renormalization of Molecular Quasiparticle Levels at Metal-Molecule Interfaces: Trends Across Binding Regimes

When an electron or a hole is added into an orbital of an adsorbed molecule the substrate electrons will rearrange in order to screen the added charge. This results in a reduction of the electron addition/removal energies as compared to the free molecule case. In this work we use a simple model to illustrate the universal trends of this renormalization mechanism as a function of the microscopic key parameters. Insight of both fundamental and practical importance is obtained by comparing GW quasiparticle energies with Hartree-Fock and Kohn-Sham calculations. We identify two different polarization mechanisms: (i) polarization of the metal (image charge formation) and (ii) polarization of the molecule via charge transfer across the interface. The importance of (i) and (ii) is found to increase with the metal density of states at the Fermi level and metal-molecule coupling strength, respectively.Comment: 4 pages, 3 figure

Leadership and self-enforcing international environmental agreements with non-negative emissions

For the widely-used linear-quadratic model of stable IEAs the key results are: (i) if the members of the IEA act in a Cournot fashion with respect to non-signatories, a stable IEA has no more than 2 signatories; (ii) if the signatories act as Stackelberg leaders, a stable IEA can have any number of signatories. These results were derived using numerical simulations and ignored the non-negativity constraint on emissions. Recent papers using analytical approaches and explicitly recognising the non-negativity constraint have suggested that with Stackelberg leadership a stable IEA has at most four signatories. Such papers have introduced non-negativity constraints by restricting parameter values to ensure interior solutions for emissions, which restricts the number of signatories. We use the more appropriate approach of directly imposing the non-negativity constraint on emissions, recognising that for some parameter values this will entail corner solutions, and show, analytically, that the key results from the literature go through.

Exposure to political disparagement humor and its impact on trust in politicians: How long does it last?

Indexación: Scopus.The experimental research that looks into the effects of political humor on an individual's attitudes toward politics and politicians does not evaluate its long-term effects. With this in mind, this study aims to determine the possible effects that being exposed to humor which belittles politicians may have on an ordinary citizen's trust in them, while at the same time it observes the possible effects that such exposure has on them and the time such effects last. Two hypotheses were tested. The first one was that humor involves less cognitive elaboration, which leads to a short-term impact on the perception of the individual. The second one was that the repetition of a message can augment the swing of such message. Also, a series of elements regarding disposition toward politicians and political affiliation were considered. Two experiments were designed. The first experiment, (N = 94), considered three groups: one exposed to political disparagement humor; one control group exposed to disparagement humor against non-politician subjects; and a control group exposed to a non-humorous political video. Trust in politicians was evaluated first at baseline, then immediately after the experimental manipulation, and once again a week after the experimental manipulation had happened. In the second experiment (N = 146), participants were randomly assigned to one experimental and two control groups. The trust in politicians of the three groups was estimated and they were sent political cartoons, non-political cartoons, and newspaper headlines regarding political topics twice a day for a week via WhatsApp. Trust in politicians among the three groups was assessed again after 1 week, and for a third time 1 week after that. As a result, it was observed that a one-off exposure to political disparagement humor affects trust in politicians negatively; however, the effect it attains is short-lived and can be explained through the political content of the item and not only humor. Also, being exposed to cartoons constantly for a week had no impact whatsoever on the way politics and politicians were perceived during the time the experiment was carried out. Possible explanations for these findings are discussed.https://www.frontiersin.org/articles/10.3389/fpsyg.2017.02236/ful

Non-equilibrium GW approach to quantum transport in nano-scale contacts

Correlation effects within the GW approximation have been incorporated into the Keldysh non-equilibrium transport formalism. We show that GW describes the Kondo effect and the zero-temperature transport properties of the Anderson model fairly well. Combining the GW scheme with density functional theory and a Wannier function basis set, we illustrate the impact of correlations by computing the I-V characteristics of a hydrogen molecule between two Pt chains. Our results indicate that self-consistency is fundamental for the calculated currents, but that it tends to wash out satellite structures in the spectral function.Comment: 5 pages, 4 figure

An infinite-horizon model of dynamic membership of international environmental agreements

Much of the literature on international environmental agreements uses static models, although most important transboundary pollution problems involve stock pollutants. The few papers that study IEAs using models of stock pollutants do not allow for the possibility that membership of the IEA may change endogenously over time. In this paper we analyse a simple infinite-horizon version of the Barrett (1994) model, in which unit damage costs increase with the stock of pollution, and countries decide each period whether to join an IEA. We show that there exists a steady-state stock of pollution with corresponding steady-state IEA membership, and that if the initial stock of pollution is below (above) steady-state then membership of the IEA declines (rises) as the stock of pollution tends to steady-state. As we increase the parameter linking damage costs to the pollution stock, initial and steady-state membership decline; in the limit, membership is small and constant over time. Keywords; self-enforcing international environmental agreements, internal and external stability, stock pollutant

Estimating Spatial Econometrics Models with Integrated Nested Laplace Approximation

Integrated Nested Laplace Approximation provides a fast and effective method for marginal inference on Bayesian hierarchical models. This methodology has been implemented in the R-INLA package which permits INLA to be used from within R statistical software. Although INLA is implemented as a general methodology, its use in practice is limited to the models implemented in the R-INLA package. Spatial autoregressive models are widely used in spatial econometrics but have until now been missing from the R-INLA package. In this paper, we describe the implementation and application of a new class of latent models in INLA made available through R-INLA. This new latent class implements a standard spatial lag model, which is widely used and that can be used to build more complex models in spatial econometrics. The implementation of this latent model in R-INLA also means that all the other features of INLA can be used for model fitting, model selection and inference in spatial econometrics, as will be shown in this paper. Finally, we will illustrate the use of this new latent model and its applications with two datasets based on Gaussian and binary outcomes

Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals

Plasmons depend strongly on dimensionality: while plasmons in three-dimensional systems start with finite energy at wavevector q = 0, plasmons in traditional two-dimensional (2D) electron gas disperse as ωp∼q√. However, besides graphene, plasmons in real, atomically thin quasi-2D materials were heretofore not well understood. Here we show that the plasmons in real quasi-2D metals are qualitatively different, being virtually dispersionless for wavevectors of typical experimental interest. This stems from a broken continuous translational symmetry which leads to interband screening; so, dispersionless plasmons are a universal intrinsic phenomenon in quasi-2D metals. Moreover, our ab initio calculations reveal that plasmons of monolayer metallic transition metal dichalcogenides are tunable, long lived, able to sustain field intensity enhancement exceeding 107, and localizable in real space (within ~20 nm) with little spreading over practical measurement time. This opens the possibility of tracking plasmon wave packets in real time for novel imaging techniques in atomically thin materials