Comparing the early research performance of PhD graduates in labor economics in Europe and the USA

This paper analyzes the early research performance of PhD graduates in labor economics, addressing the following questions: Are there major productivity differences between graduates from American and European institutions? If so, how relevant is the quality of the training received (i.e. ranking of institution and supervisor) and the research environment in the subsequent job placement institution? The population under study consists of labor economics PhD graduates who received their degree in the years 2000 to 2005 in Europe or the USA. Research productivity is evaluated alternatively as the number of publications or the quality-adjusted number of publications of an individual. When restricting the analysis to the number of publications, results suggest a higher productivity by graduates from European universities than from USA universities, but this difference vanishes when accounting for the quality of the publication. The results also indicate that graduates placed at American institutions, in particular top ones, are likely to publish more quality-adjusted articles than their European counterparts. This may be because, when hired, they already have several good acceptances or because of more focused research efforts and clearer career incentives.

Semigroup analysis of structured populations with distributed states-at-birth arising in mathematical aquaculture

Motivated by the modelling of structured parasite populations in aquaculture we consider a class of physiologically structured population models, where individuals may be recruited into the population at different sizes in general. That is, we consider a size-structured population model with distributed states-at-birth. The mathematical model which describes the evolution of such a population is a first order nonlinear partial integro-differential equation of hyperbolic type. First, we use positive perturbation arguments and utilise results from the spectral theory of semigroups to establish conditions for the existence of a positive equilibrium solution of our model. Then we formulate conditions that guarantee that the linearised system is governed by a positive quasicontraction semigroup on the biologically relevant state space. We also show that the governing linear semigroup is eventually compact, hence growth properties of the semigroup are determined by the spectrum of its generator. In case of a separable fertility function we deduce a characteristic equation and investigate the stability of equilibrium solutions in the general case using positive perturbation arguments.

A critical analysis of dimensions and curve fitting practice in economics

When dealing with sustainability we are concerned with the biophysical as well as the monetary aspects of economic and ecological interactions. This multidimensional approach requires that special attention is given to dimensional issues in relation to curve fitting practice in economics. Unfortunately, many empirical and theoretical studies in economics, as well as in ecological economics, apply dimensional numbers in exponential or logarithmic functions. We show that it is an analytical error to put a dimensional unit x into exponential functions ( a x ) and logarithmic functions ( x a log ). Secondly, we investigate the conditions of data sets under which a particular logarithmic specification is superior to the usual regression specification. This analysis shows that logarithmic specification superiority in terms of least square norm is heavily dependent on the available data set. The last section deals with economists’ “curve fitting fetishism”. We propose that a distinction be made between curve fitting over past observations and the development of a theoretical or empirical law capable of maintaining its fitting power for any future observations. Finally we conclude this paper with several epistemological issues in relation to dimensions and curve fitting practice in economics

Deliberative ecological economics: emergence and research issues

We discuss the recent emergence of "deliberative ecological economics", a field that highlights the potential of deliberation for improving environmental governance. We locate the emergence of this literature in the long concern in ecological economics over the policy implications of limited views of human action and its encounter with deliberative democracy scholarship and the model of communicative rationality as an alternative to utilitarianism. Considering criticisms over methods used and the focus of research in deliberative decision-making, we put forward a research agenda for deliberative ecological economics. Given the promising potential of deliberative processes for improving the effectiveness and legitimacy of environmental decision-making, work in this area could help advance both theory and practice in environmental governance.

Mathematical description of bacterial traveling pulses

The Keller-Segel system has been widely proposed as a model for bacterial waves driven by chemotactic processes. Current experiments on E. coli have shown precise structure of traveling pulses. We present here an alternative mathematical description of traveling pulses at a macroscopic scale. This modeling task is complemented with numerical simulations in accordance with the experimental observations. Our model is derived from an accurate kinetic description of the mesoscopic run-and-tumble process performed by bacteria. This model can account for recent experimental observations with E. coli. Qualitative agreements include the asymmetry of the pulse and transition in the collective behaviour (clustered motion versus dispersion). In addition we can capture quantitatively the main characteristics of the pulse such as the speed and the relative size of tails. This work opens several experimental and theoretical perspectives. Coefficients at the macroscopic level are derived from considerations at the cellular scale. For instance the stiffness of the signal integration process turns out to have a strong effect on collective motion. Furthermore the bottom-up scaling allows to perform preliminary mathematical analysis and write efficient numerical schemes. This model is intended as a predictive tool for the investigation of bacterial collective motion.

Reconsideration of dimensions and curve fitting practice in economics ellaborating on Georgescu-Roegen’s economic methodology

This paper is to examine the proper use of dimensions and curve fitting practices elaborating on Georgescu-Roegen’s economic methodology in relation to the three main concerns of his epistemological orientation. Section 2 introduces two critical issues in relation to dimensions and curve fitting practices in economics in view of Georgescu-Roegen’s economic methodology. Section 3 deals with the logarithmic function (ln z) and shows that z must be a dimensionless pure number, otherwise it is nonsensical. Several unfortunate examples of this analytical error are presented including macroeconomic data analysis conducted by a representative figure in this field. Section 4 deals with the standard Cobb-Douglas function. It is shown that the operational meaning cannot be obtained for capital or labor within the Cobb-Douglas function. Section 4 also deals with economists "curve fitting fetishism". Section 5 concludes thispaper with several epistemological issues in relation to dimensions and curve fitting practices in economics.

Complementarities between mathematical and computational modeling: the case of the repeated Prisoners' Dilemma

We study the properties of the well known Replicator Dynamics when applied to a finitely repeated version of the Prisoners' Dilemma game. We characterize the behavior of such dynamics under strongly simplifying assumptions (i.e. only 3 strategies are available) and show that the basin of attraction of defection shrinks as the number of repetitions increases. After discussing the difficulties involved in trying to relax the 'strongly simplifying assumptions' above, we approach the same model by means of simulations based on genetic algorithms. The resulting simulations describe a behavior of the system very close to the one predicted by the replicator dynamics without imposing any of the assumptions of the mathematical model. Our main conclusion is that mathematical and computational models are good complements for research in social sciences. Indeed, while computational models are extremely useful to extend the scope of the analysis to complex scenarios hard to analyze mathematically, formal models can be useful to verify and to explain the outcomes of computational models.

An approximate mathematical model for solidification of a flowing liquid in a microchannel

A mathematical model is developed to analyse the combined flow and solidification of a liquid in a small pipe or two-dimensional channel. In either case the problem reduces to solving a single equation for the position of the solidification front. Results show that for a large range of flow rates the closure time is approximately constant, and the value depends primarily on the wall temperature and channel width. However, the ice shape at closure will be very different for low and high fluxes. As the flow rate increases the closure time starts to depend on the flow rate until the closure time increases dramatically, subsequently the pipe will never close.

Mathematical modeling and analysis of the interaction of populations of bacteria and bacteriophages within chicken intestine

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Ideas, Possibilities and Limitations of Sustainable Economic Policy – the Example of Ecological Economics

A mesura que el suport del creixement econòmic constitueix un objectiu fonamental de la formulació de polítiques econòmiques, cal assenyalar que aquest tipus de creixement està limitat naturalment per un planeta finit. Aquest article argumenta que, des del punt de vista de la justícia intergeneracional, la realització d'un concepte de desmaterialització i, com a efecte, d'una economia que no creix (en el sentit de dissociació absoluta del creixement econòmic i consum d'energia i materials) es pot justificar. Per tant, el creixement pot ser també entesa com la millora de la qualitat de vida sobretot en comptes d'ampliar quantitats escarpats de sortida. Per tant, una dràstica reducció del cabal de material es necessita, sobretot en els països d'alts ingressos. Després de presentar alguns crítica de les propostes, en el focus d'aquest article es dibuixen en els arguments de per què la política econòmica en el futur han de ser etiquetats com "ecològic" i, a continuació, les opcions de posar en acció les idees del teòric presentat marc en tasques manejables polítiques seran discutides. En aquest cas, s'argumentarà que l'enfocament clàssic de internalització d'efectes externs sovint seguides de decisions de política econòmica ortodoxa no és completament capaç de reflectir canvis ecològics en les estructures de preus dels mercats. Per tant, formal (industrial i l'establiment de la política de consum) i institucions informals (llars) representen punts clau de la política econòmica sostenible, assenyalant l'individu com així com la responsabilitat col · lectiva per omplir aquest buit substancial.

On the foundations of well-being economics and policy

When one wishes to implement public policies, there is a previous need of comparing different actions and valuating and evaluating them to assess their social attractiveness. Recently the concept of well-being has been proposed as a multidimensional proxy for measuring societal prosperity and progress; a key research topic is then on how we can measure and evaluate this plurality of dimensions for policy decisions. This paper defends the thesis articulated in the following points: 1. Different metrics are linked to different objectives and values. To use only one measurement unit (on the grounds of the so-called commensurability principle) for incorporating a plurality of dimensions, objectives and values, implies reductionism necessarily. 2. Point 1) can be proven as a matter of formal logic by drawing on the work of Geach about moral philosophy. This theoretical demonstration is an original contribution of this article. Here the distinction between predicative and attributive adjectives is formalised and definitions are provided. Predicative adjectives are further distinguished into absolute and relative ones. The new concepts of set commensurability and rod commensurability are introduced too. 3. The existence of a plurality of social actors, with interest in the policy being assessed, causes that social decisions involve multiple types of values, of which economic efficiency is only one. Therefore it is misleading to make social decisions based only on that one value. 4. Weak comparability of values, which is grounded on incommensurability, is proved to be the main methodological foundation of policy evaluation in the framework of well-being economics. Incommensurability does not imply incomparability; on the contrary incommensurability is the only rational way to compare societal options under a plurality of policy objectives. 5. Weak comparability can be implemented by using multi-criteria evaluation, which is a formal framework for applied consequentialism under incommensurability. Social Multi-Criteria Evaluation, in particular, allows considering both technical and social incommensurabilities simultaneously.

The Simple Economics of Conglomeration with Bankruptcy Costs: Separate or Joint Financing?

Which projects should be financed through separate non-recourse loans (or limited- liability companies) and which should be bundled into a single loan? In the pres- ence of bankruptcy costs, this conglomeration decision trades off the benefit of co- insurance with the cost of risk contamination. This paper characterize this tradeoff for projects with binary returns, depending on the mean, variability, and skewness of returns, the bankruptcy recovery rate, the correlation across projects, the number of projects, and their heterogeneous characteristics. In some cases, separate financing dominates joint financing, even though it increases the interest rate or the probability of bankruptcy.

Aitchison Geometry for Probability and Likelihood as a new approach to mathematical statistics

The Aitchison vector space structure for the simplex is generalized to a Hilbert space structure A2(P) for distributions and likelihoods on arbitrary spaces. Centralnotations of statistics, such as Information or Likelihood, can be identified in the algebraical structure of A2(P) and their corresponding notions in compositional data analysis, such as Aitchison distance or centered log ratio transform.In this way very elaborated aspects of mathematical statistics can be understoodeasily in the light of a simple vector space structure and of compositional data analysis. E.g. combination of statistical information such as Bayesian updating,combination of likelihood and robust M-estimation functions are simple additions/perturbations in A2(Pprior). Weighting observations corresponds to a weightedaddition of the corresponding evidence.Likelihood based statistics for general exponential families turns out to have aparticularly easy interpretation in terms of A2(P). Regular exponential families formfinite dimensional linear subspaces of A2(P) and they correspond to finite dimensionalsubspaces formed by their posterior in the dual information space A2(Pprior).The Aitchison norm can identified with mean Fisher information. The closing constant itself is identified with a generalization of the cummulant function and shown to be Kullback Leiblers directed information. Fisher information is the local geometry of the manifold induced by the A2(P) derivative of the Kullback Leibler information and the space A2(P) can therefore be seen as the tangential geometry of statistical inference at the distribution P.The discussion of A2(P) valued random variables, such as estimation functionsor likelihoods, give a further interpretation of Fisher information as the expected squared norm of evidence and a scale free understanding of unbiased reasoning

A mathematical excursion: From the three-door problem to a Cantor-type perfect set

We start with a generalization of the well-known three-door problem:the n-door problem. The solution of this new problem leads us toa beautiful representation system for real numbers in (0,1] as alternated series, known in the literature as Pierce expansions. A closer look to Pierce expansions will take us to some metrical properties of sets defined through the Pierce expansions of its elements. Finally, these metrical properties will enable us to present 'strange' sets, similar to the classical Cantor set.