By polymorphic Π1 types we mean types of the polymorphic lambda calculus (system F) in which Π only occurs positively. For such types the question of inhabitation is decidable and observational equivalence corresponds to βη-equivalence and is representable by a term. Furthermore, in the PER-model based on untyped λ-terms universality holds for all Π1 types (all elements can be typed). At the en...

One or Many Kuznets Curves? Short and Long Run Effects of the Impact of Skill-Biased Technological Change on Income Inequality We draw on a dynamical two-sector model and on a calibration exercise to study the impact of a skill-biased technological shock on the growth path and income distribution of a developing economy. The model builds on the theoretical framework developed by Silverberg and ...

In an increasingly crowded marketplace, retailers need innovative ways of promoting products to their consumers. E-commerce retailers have utilized to great effect lists of top ranked products to promote product sales; the higher the sales rank, the more likely consumers buy that product. This influence to buy, based on observing what others bought is known as observational learning (OL). Prior...

Fickle is a class-based object oriented imperative language, which extends Java with object re-classification. In this paper, we introduce a natural observational equivalence on Fickle programs. This is a contextual equivalence on main methods with respect to a given sequence of class definitions, i.e. a program. To study it, we use the formal computational model for OO-programming based on coa...

We prove that observational equivalence of IA3 + Y0 (3rdorder Idealized Algol with 0th-order recursion) is equivalent to the DPDA Equivalence Problem, and hence decidable. This completes the classification of decidable fragments of Idealized Algol. We also prove that observational approximation of IA1 + Y0 is undecidable by reducing the DPDA Containment Problem to it.

Three important results about the expressivity of a modal logic L are the Characterization Theorem (that identifies a modal logic L as a fragment of a better known logic), the Definability theorem (that provides conditions under which a class of L-models can be defined by a formula or a set of formulas of L), and the Separation Theorem (that provides conditions under which two disjoint classes ...

Classical Linear Logic (CLL) has long inspired readings of its proofs as communicating processes. Wadler’s CP calculus is one of these readings. Wadler gave CP an operational semantics by selecting a subset of the cut-elimination rules of CLL to use as reduction rules. This semantics has an appealing close connection to the logic, but does not resolve the status of the other cut-elimination rul...

We employ automata over infinite alphabets to capture the semantics of a finitary fragment of ML with ground-type references. Our approach is founded on game semantics, which allows us to translate programs into automata in such a way that contextual equivalence is characterized by a finitary notion of bisimilarity. As a corollary, we derive a decidability result for a class of first-order prog...

We develop observable restrictions of well-known theories of bargaining over money. We suppose that we observe a finite data set of bargaining outcomes, including data on allocations and disagreement points, but no information on utility functions. We ask when a given theory could generate the data. We show that if the disagreement point is fixed and symmetric, the Nash, utilitarian, and egalit...

I written elsewhere: “Where there exists a critical mass of scholars working on similar sets of questions—critiquing and building on one another’s work—knowledge accumulation is more likely to occur.”1 It is with this statement in mind that I proceed with my response to Michael Nelson’s thoughtful critique. Rather than a point-by-point rebuttal, I will focus on three of the most interesting and...