6,486 research outputs found
COULD WELFARE OPTIMALITY BE ACHIEVED WITH EXTENSIVE DATA INFORMATION?
This paper examines whether the Danish management system achieves welfare maximisation. For cod in the North Sea, Skagerrak, and Kattegat, rations are used. It is shown that rations raise substantial information requirements and that the existing allocation of rations is inoptimal. In addition, a linear programming model is used to show that there is considerable overcapacity in the Danish trawler fleet in the Baltic Sea. Danish fisheries managers have access to an extensive data set, and with the available information it would be possible to secure a welfare optimum.Resource /Energy Economics and Policy,
Reforming the EU Sugar Policy
This article presents and analyses the impacts of the EU sugar policy. Particular attention is given to the modelling of the quite complex policy and the calibration of the global general equilibrium model at the member state level. Two scenarios are analysed, namely a reduction in the intervention price of sugar and the sugar quota. It is found that the economic impacts of the two scenarios are quite different in terms of the effects on European production and trade in sugar as well in terms of efficiency. The impacts for developing countries also differ considerably across the two scenarios.EU sugar policy, general equilibrium modelling, reform scenarios, Agricultural and Food Policy, C68, D58, Q17, Q18,
Late glacial dynamics on the continental shelf of NE-Greenland - implications from submarine landforms
Favorable sea-ice conditions gave way to an acoustic survey offshore NE-Greenland in 2009. The acquired data set clearly depicts an area of sediment ridges in an area of at app. 18 x 9 km. The ridges are found in water depths between 270 and 350 m. The sediment ridges expand between 2,5 â 9 km, are 50 â 250 m wide and between 10 and 25 m high. In profile and without exception, these ridges are characterized by steep slopes towards West and gentle slopes towards East. Their internal structure, imaged by parametric echo-sounding data, shows that they have been deposited on a rather plain surface, thus representing positive sedimentation features rather than erosive remnant structures. Their curved shape, joint orientation and position on a basal till surface indicate their origin from glacial dynamics. We interpret these ridges as a set of terminal moraines. Since they are positioned on a basal till that extends further east, we consider these moraines to reflect short-lived re-advances during an overall recession of the ice stream. This is direct evidence for a highly dynamic behavior of an ice stream from the NE-Greenland Ice Sheet. The ages for these re-advances can be inferred from a thin sedimentary drape indicating a timing between Late Glacial and early Holocene
The Evolution of Conventions under Incomplete Information
We formulate an evolutionary learning process in the spirit of Young (1993) for games of incomplete information. The process involves trembles. For many games, if the amount of trembling is small, play will be in accordance with the games' (semi-strict) Bayesian equilibria most of the time. This supports the notion of Bayesian equilibrium. Further, often play will most of the time be in accordance with exactly one Bayesian equilibrium. This gives a selection among the Bayesian equilibria. For two specific games of economic interest we characterize this selection. The first is an extension to incomplete information of the prototype strategic conflict known as Chicken. The second is an incomplete information bilateral monopoly, which is also an extension to incomplete information of Nash's demand game, or a simple version of the so-called sealed bid double auction. For both games selection by evolutionary learning is in favor of Bayesian equilibria where some types of players fail to coordinate, such that the outcome is inefficient.
The evolution of conventions under incomplete information
We formulate an evolutionary learning process in the spirit of Young (1993a) for games of incomplete information. The process involves trembles. For many games, if the amount of trembling is small, play will be in accordance with the games' (semi- strict) Bayesian equilibria most of the time. This supports the notion of Bayesian equilibrium. Further, often play will most of the time be in accordance with exactly one Bayesian equilibrium. This gives a selection among the Bayesian equilibria. For two specific games of economic interest we characterize this selection. The first is an extension to incomplete information of the prototype strategic conflict known as Chicken. The second is an incomplete information bilateral monopoly, which is also an extension to incomplete information of Nash's demand game, or a simple version of the so-called sealed bid double auction. For both games selection by evolutionary learning is in favor of Bayesian equilibria where some types of players fail to coordinate, such that the outcome is inefficient.Games of incomplete information, Bayesian equilibrium, evolution, learning, conventions
Multiconfigurational Short-Range Density-Functional Theory for Open-Shell Systems
Many chemical systems cannot be described by quantum chemistry methods based
on a singlereference wave function. Accurate predictions of energetic and
spectroscopic properties require a delicate balance between describing the most
important configurations (static correlation) and obtaining dynamical
correlation efficiently. The former is most naturally done through a
multiconfigurational (MC) wave function, whereas the latter can be done by,
e.g., perturbation theory. We have employed a different strategy, namely, a
hybrid between multiconfigurational wave functions and density-functional
theory (DFT) based on range separation. The method is denoted by MC short-range
(sr) DFT and is more efficient than perturbative approaches as it capitalizes
on the efficient treatment of the (short-range) dynamical correlation by DFT
approximations. In turn, the method also improves DFT with standard
approximations through the ability of multiconfigurational wave functions to
recover large parts of the static correlation. Until now, our implementation
was restricted to closed-shell systems, and to lift this restriction, we
present here the generalization of MC-srDFT to open-shell cases. The additional
terms required to treat open-shell systems are derived and implemented in the
DALTON program. This new method for open-shell systems is illustrated on
dioxygen and [Fe(H2O)6]3+.Comment: 37 pages, 3 figures, 4 tables, 1 appendix and 79 references Changes
in v2: 1) Appendix B and reference 81 removed 2) Removed dublicated reference
and corrected reference 31. 3) Added spin-charge cross terms to GGA (Appendix
A). Code changed accordingly and GGA results recalculated. All GGA results
are revised -only small modifications observed. Conclusions are unchange
Linear interpolation method in ensemble Kohn-Sham and range-separated density-functional approximations for excited states
Gross-Oliveira-Kohn density functional theory (GOK-DFT) for ensembles is in
principle very attractive, but has been hard to use in practice. A novel,
practical model based on GOK-DFT for the calculation of electronic excitation
energies is discussed. The new model relies on two modifications of GOK-DFT:
use of range separation and use of the slope of the linearly-interpolated
ensemble energy, rather than orbital energies. The range-separated approach is
appealing as it enables the rigorous formulation of a multi-determinant
state-averaged DFT method. In the exact theory, the short-range density
functional, that complements the long-range wavefunction-based ensemble energy
contribution, should vary with the ensemble weights even when the density is
held fixed. This weight dependence ensures that the range-separated ensemble
energy varies linearly with the ensemble weights. When the (weight-independent)
ground-state short-range exchange-correlation functional is used in this
context, curvature appears thus leading to an approximate weight-dependent
excitation energy. In order to obtain unambiguous approximate excitation
energies, we propose to interpolate linearly the ensemble energy between
equiensembles. It is shown that such a linear interpolation method (LIM) can be
rationalized and that it effectively introduces weight dependence effects. As
proof of principle, LIM has been applied to He, Be, H in both equilibrium
and stretched geometries as well as the stretched HeH molecule. Very
promising results have been obtained for both single (including charge
transfer) and double excitations with spin-independent short-range local and
semi-local functionals. Even at the Kohn--Sham ensemble DFT level, that is
recovered when the range-separation parameter is set to zero, LIM performs
better than standard time-dependent DFT.Comment: 26 pages, 8 figure
Alternative separation of exchange and correlation energies in range-separated density-functional perturbation theory
An alternative separation of short-range exchange and correlation energies is
used in the framework of second-order range-separated density-functional
perturbation theory. This alternative separation was initially proposed by
Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] and relies on a long-range
interacting wavefunction instead of the non-interacting Kohn-Sham one. When
second-order corrections to the density are neglected, the energy expression
reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf,
where "f" stands for "full-range integrals" as the regular full-range
interaction appears explicitly in the energy expression when expanded in
perturbation theory. In contrast to usual RSDH functionals, RSDHf describes the
coupling between long- and short-range correlations as an orbital-dependent
contribution. Calculations on the first four noble-gas dimers show that this
coupling has a significant effect on the potential energy curves in the
equilibrium region, improving the accuracy of binding energies and equilibrium
bond distances when second-order perturbation theory is appropriate.Comment: 5 figure
Bisimulation and expressivity for conditional belief, degrees of belief, and safe belief
Plausibility models are Kripke models that agents use to reason about
knowledge and belief, both of themselves and of each other. Such models are
used to interpret the notions of conditional belief, degrees of belief, and
safe belief. The logic of conditional belief contains that modality and also
the knowledge modality, and similarly for the logic of degrees of belief and
the logic of safe belief. With respect to these logics, plausibility models may
contain too much information. A proper notion of bisimulation is required that
characterises them. We define that notion of bisimulation and prove the
required characterisations: on the class of image-finite and preimage-finite
models (with respect to the plausibility relation), two pointed Kripke models
are modally equivalent in either of the three logics, if and only if they are
bisimilar. As a result, the information content of such a model can be
similarly expressed in the logic of conditional belief, or the logic of degrees
of belief, or that of safe belief. This, we found a surprising result. Still,
that does not mean that the logics are equally expressive: the logics of
conditional and degrees of belief are incomparable, the logics of degrees of
belief and safe belief are incomparable, while the logic of safe belief is more
expressive than the logic of conditional belief. In view of the result on
bisimulation characterisation, this is an equally surprising result. We hope
our insights may contribute to the growing community of formal epistemology and
on the relation between qualitative and quantitative modelling
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