The aim of this paper is to compute a simplicial cohomology group of some specific digital images. Then we define ringand algebra structures of a digital cohomology with the cup product. Finally, we prove a special case of the Borsuk-Ulam theorem fordigital images.

We develop a framework for the analysis of dynamic oligopolies with persistant sources of asymmetric information that enables applied analysis of situations of empirical importance that have been difficult to deal with. The framework generates policies which are “relatively” easy for agents to use while still being optimal in a meaningful sense, and is amenable to empirical research in that its...

The percentage of exporters and multinational enterprises (MNEs) varies substantially across industries. We extend the firm heterogeneity model presented in Helpman et al. (2004) to derive testable predictions about the prevalence of these internationalized modes. The model indicates that intra-industry firm heterogeneity and R&D intensity play large roles in the inter-industry variation of the...

We survey an emerging literature at the intersection of organizational economics and international trade. We argue that a proper modelling of the organizational aspects of production provides valuable insights on the aggregate workings of the world economy. In reviewing the literature, we describe certain predictions of standard models that are a¤ected or even overturned when organizational dec...

We extend the class of quality-ladder growth models (Grossman-Helpman (1991), Segerstrom (1998) and others), to encompass an economy with asymmetric fundamentals. In contrast with the standard framework, in our model industries may differ in terms of their innovative potential (quality jumps and arrival rates) and consumers’ preferences. This extension allows us to bring industrial policy back ...

The purpose of this paper is to set endogenous or new growth theory against broader developments within economics as a discipline. As a topic, irrespective of its intellectual antecedents, endogenous growth theory is extremely recent, only dating back in acknowledged published form to Romer's (1986) article which is usually coupled with Lucas' (1988) contribution. Within a decade, the literatur...

Baer has shown that, for a group G, finiteness of G=Zi(G) implies finiteness of ɣi+1(G). In this paper we will show that the converse is true provided that G=Zi(G) is finitely generated. In particular, when G is a finite nilpotent group we show that |G=Zi(G)| divides |ɣi+1(G)|d′ i(G), where d′i(G) =(d( G /Zi(G)))i.

In this paper, I show that the increasing similarity in GDPs among OECD country pairs leads to higher bilateral trade to GDP ratios. This finding provides some support for the prediction of Helpman [J. Jpn. Int. Econ. 1 (1987) 62], whose model explains intra-industry trade that is prevalent among developed countries. I also show that Helpman’s prediction is rejected for non-OECD countries, amon...

This paper introduces service innovation in the proximity-concentration trade-off model of trade and FDI (Helpman, Melitz and Yeaple, 2004). The idea is that innovation will have two main effects on service firms’ choice between exports and FDI. First, innovative firms will on average have higher productivity levels than non-innovative enterprises. Secondly, innovators will have to pay a higher...

This paper investigates the impact of geography on technological diffusion via international trade and proposes to re-examine the contribution of Coe, Helpman and Hoffmaister to the knowledge spillovers literature. Using a gravitational model, we first confirm the negative effect of physical distance on imports. We also show that geographic proximity contributes to more technological diffusion ...