A Classical Realizability Model arising from a Stable Model of Untyped Lambda Calculus

We study a classical realizability model (in the sense of J.-L. Krivine) arising from a model of untyped lambda calculus in coherence spaces. We show that this model validates countable choice using bar recursion and bar induction

Models of Intuitionistic Set Theory in Subtoposes of Nested Realizability Toposes

With every pca $\mathcal{A}$ and subpca $\mathcal{A}_\#$ we associate the nested realizability topos $\mathsf{RT}(\mathcal{A},\mathcal{A}_\#)$ within which we identify a class of small maps $\mathcal{S}$ giving rise to a model of intuitionistic set theory within $\mathsf{RT}(\mathcal{A},\mathcal{A}_\#)$. For every subtopos $\mathcal{E}$ of such a nested realizability topos we construct an induced class $\mathcal{S_E}$ of small maps in $\mathcal{E}$ giving rise to a model of intuitionistic set theory within $\mathcal{E}$. This covers relative realizability toposes, modified relative realizability toposes, the modified realizability topos and van den Berg's recent Herbrand topos

Classical logic, continuation semantics and abstract machines

One of the goals of this paper is to demonstrate that denotational semantics is useful for operational issues like implementation of functional languages by abstract machines. This is exemplified in a tutorial way by studying the case of extensional untyped call-by-name λ-calculus with Felleisen's control operator 𝒞. We derive the transition rules for an abstract machine from a continuation semantics which appears as a generalization of the ¬¬-translation known from logic. The resulting abstract machine appears as an extension of Krivine's machine implementing head reduction. Though the result, namely Krivine's machine, is well known our method of deriving it from continuation semantics is new and applicable to other languages (as e.g. call-by-value variants). Further new results are that Scott's D∞-models are all instances of continuation models. Moreover, we extend our continuation semantics to Parigot's λμ-calculus from which we derive an extension of Krivine's machine for λμ-calculus. The relation between continuation semantics and the abstract machines is made precise by proving computational adequacy results employing an elegant method introduced by Pitts

Production Effects of Agri-environmental "Green Box" Payments: Empirical Results from the EU

Agri-environmental programs are part of the green box of the GATT Uruguay Round and are supposed to "have no, or at most minimal trade distorting effects or effects on production." In addition, "the amount of payment shall be limited to the extra costs or loss of income involved in complying with the government programme." Utilizing farm accounting data we estimate the effects on yields for ten agri-environmental programs in Austria, which account for 12% of EU's budget expenditures for agri-environmental programs. Only three out of these ten programs have significant negative effects on yields, while one program has a significant positive impact and the rest has no significant impact. These results suggest that there are serious windfall profits associated with some of these programs.agri-environmental programs, Green box, WTO, Common Agricultural Policy, decoupling, Environmental Economics and Policy, F16, Q56,

Output Effects of Agri-environmental Programs of the EU

By definition agri-environmental programs of the EU aim not only at improving environmental quality, but also at reducing overproduction while supporting farm income. The aim of the study is to empirically measure the success of agri-environmental programs in regard to the objective of reducing or stabilizing production levels.Environmental Economics and Policy,