Arbitrage in markets with bid-ask spreads

In this paper a finite discrete time market with an arbitrary state space and bid-ask spreads is considered. The notion of an equivalent bid-ask martingale measure (EBAMM) is introduced and the fundamental theorem of asset pricing is proved using (EBAMM) as an equivalent condition for no-arbitrage. The Cox-Ross-Rubinstein model with bid-ask spreads is presented as an application of our results.Comment: 18 pages, 3 figure

Livestock intensification and smallholders

"This essay describes the views of Philippines livestock sector stakeholders concerning the events and issues associated with the rapid rise in hog and poultry production, based on rapid reconnaissance interviews and gray literature from studies in Southern Luzon, Iloilo and Northern Mindanao, and the impressions of the authors. Changing demographic patterns, decentralized eco-governance, trade liberalization, and health and environmental policies have major impacts on further livestock intensification and on increasing scale of operations. Six factors appear to affect small farmers' decisions to intensify or raise livestock, or remain in the livestock industry. These are 1) access to financial capital; 2) technical knowledge about livestock production and their sources of information; 3) social capital expressed as trust in integrators, in the primary buyers of the livestock, and in government; 4) demographic characteristics, such as gender and age; 5) farmer perceptions of the policy environment (prices, feeds, health and environmental policies, and the local ordinances affecting the livestock sector); and 6) access to reliable markets for outputs across the year." Authors' Abstractlivestock ,small farms ,

Dirichlet eigenfunctions on the cube, sharpening the Courant nodal inequality

This paper is devoted to the refine analysis of Courant's theorem for the Dirichlet Laplacian. Many papers (and some of them quite recent) have investigated in which cases this inequality in Courant's theorem is an equality: Pleijel, Helffer--Hoffmann-Ostenhof--Terracini, Helffer--Hoffmann-Ostenhof, B\'erard-Helffer, Helffer--Persson-Sundqvist, L\'ena, Leydold. All these results were devoted to $(2D)$-cases in open sets in $\mathbb R^2$ or in surfaces like $\mathbb S^2$ or $\mathbb T^2$. The aim of the current paper is to look for analogous results for domains in $\mathbb{R}^3$ and, as $\AA.$Pleijel was suggesting in his 1956 founding paper, for the simplest case of the cube. More precisely, we will prove that the only eigenvalues of the Dirichlet Laplacian which are Courant sharp are the two first eigenvalues

Extremal first Dirichlet eigenvalue of doubly connected plane domains and dihedral symmetry

We deal with the following eigenvalue optimization problem: Given a bounded domain $D\subset \R^2$, how to place an obstacle $B$ of fixed shape within $D$ so as to maximize or minimize the fundamental eigenvalue $\lambda_1$ of the Dirichlet Laplacian on $D\setminus B$. This means that we want to extremize the function $\rho\mapsto \lambda_1(D\setminus \rho (B))$, where $\rho$ runs over the set of rigid motions such that $\rho (B)\subset D$. We answer this problem in the case where both $D$ and $B$ are invariant under the action of a dihedral group $\mathbb{D}_n$, $n\ge2$, and where the distance from the origin to the boundary is monotonous as a function of the argument between two axes of symmetry. The extremal configurations correspond to the cases where the axes of symmetry of $B$ coincide with those of $D$.Comment: To appear in SIAM Journal on Mathematical Analysi

Where to place a spherical obstacle so as to maximize the second Dirichlet eigenvalue

We prove that among all doubly connected domains of $\mathbb{R}^n$ bounded by two spheres of given radii, the second eigenvalue of the Dirichlet Laplacian achieves its maximum when the spheres are concentric (spherical shell). The corresponding result for the first eigenvalue has been established by Hersch in dimension 2, and by Harrell, Kr\"oger and Kurata and Kesavan in any dimension. We also prove that the same result remains valid when the ambient space $\mathbb{R}^n$ is replaced by the standard sphere $\mathbb{S}^n$ or the hyperbolic space $\mathbb{H}^n$ .Comment: To appear in Communications in Pure and Applied Analysi

COMPETITIVENESS OF NATIONS IN THE GLOBALIZATION ERA: IS THE (IN)EXISTENCE OF A COLLECTIVE STRATEGY RELEVANT?

Economic globalization puts businesses and countries facing new opportunities and challenges and engenders a high degree of uncertainty/risk. Portugal, facing this new global environment, has been experiencing poor economic performance, growing in the last decade at a rate lower than the European Union’s average. How to seize opportunities and overcome challenges, while at the same time ensuring the desired convergence? This challenge is put in terms of the relations between the regulatory and economic policies of States and the competitiveness of nation-States. Using concrete examples, in particular the Portuguese case, we will attempt to answer the question: does the existence (or absence) of a collective strategy, understood as a concerted strategy between the State and companies, their associations and other institutions, produce significant impact on the competitiveness of Nations? To answer this question, the analysis will focus on the following topics: challenges posed by globalization in terms of competitiveness of countries; evolution of the Portuguese economy, between 1975 and 2007, compared to those of Finland, Ireland and South Korea, countries of recognized success in the context of globalization; lessons that can be drawn concerning the presence or absence of a collective strategy and its impact on the competitiveness of these countries.globalization; competitiveness; institutions; total factor productivity; collective strategy; Portugal

Ag econ angst crisis revisited: a rejoinder

Poverty reduction has been an underlying goal of governments and the development community since the Second World War, but it was the 1973 Nairobi address of Robert S. McNamara, then President of the World Bank, that created a new commitment to directly address poverty reduction in the quest for development (McNamara 1973). More than half a century after the war and close to 30 years after Robert McNamara’s speech, poverty is still rampant in many parts of the globe. Reflections on why this scourge remains, and what we as agricultural economists can do about it, were the driving forces behind our paper with the late John L. Dillon entitled ‘Agricultural economists and world poverty: progress and prospects’ (Rola-Rubzen et al. 2001). The part of our paper that Johnson, Rossmiller and Sandiford-Rossmiller (JRS) have reacted to was deliberately provocative to stimulate thinking on ways to combat poverty. We are pleased that someone has taken the bait. As the two surviving authors, we find ourselves in agreement with much that JRS have written. However, in preparing this rejoinder we have sadly missed John Dillon, especially his broad international experience. We note that in several respects JRS amplify and support some of our points, as well as adding a new perspective of their own, dealing with the new institutional economics. We find it hard to work out just where they differ from us.Teaching/Communication/Extension/Profession,

Modifications in the structure of the lichen Cladonia thallus in the aftermath of habitat contamination and implications for its heavy-metal accumulation capacity

Phenotypic traits of lichens can be greatly modified by environmental factors. Granulose thalli on soil and podetia, densely covered with granules, referring to common and widespread lichen Cladonia cervicornis subsp. verticillata were found near zinc smelter. The granules are stratified, filled with fungal medulla and heavily encrusted with calcium oxalate weddellite crystals, not observed on regularly developed thalli of the species. Phylogenetic analysis revealed that deformed granulose forms belong to this taxon, showing that the phenotypic plasticity of the lichens of Cladonia can lead to the emergence of features that do not coincide with the taxonomic definition of the species. The heavy-metal accumulation capacity of both granulose and regular form of primary and secondary lichen thallus, in relation to the element content in corresponding substrate, was determined. Granulose-modified thalli accumulate greater amounts of heavy metals than regular ones, meaning that the bioaccumulation property of a given species may be greatly affected by morphological modifications. The granulose forms are also characterised by considerably higher ratios of Cd, Pb and As concentrations in lichen samples in relation to the corresponding substrates than regular ones. This means that collection of variously formed thalli should be avoided in biomonitoring sampling procedures. The results indicate that a substantial part of the element load, in particular zinc, in the examined lichen thalli collected near the smelter originates from atmospheric fallout