Back to the Future: Economic Self-Organisation and Maximum Entropy Prediction

This paper shows that signal restoration methodology is appropriate for predicting the equilibrium state of certain economic systems. A formal justification for this is provided by proving the existence of finite improvement paths in object allocation problems under weak assumptions on preferences, linking any initial condition to a Nash equilibrium. Because a finite improvement path is made up of a sequence of systematic best-responses, backwards movement from the equilibrium back to the initial condition can be treated like the realisation of a noise process. This underpins the use of signal restoration to predict the equilibrium from the initial condition, and an illustration is provided through an application of maximum entropy signal restoration to the Schelling model of segregation

Back to the Future: A Simple Solution to Schelling Segregation

The maximum entropy methodology is applied to the Schelling model of urban segregation in order to obtain a reliable prediction of the stable configuration of the system without resorting to numerical simulations. We show that this approach also provides an implicit equation describing the distribution of agents over a city which allows for directly assessing the effect of model parameters on the solution. Finally, we discuss the information theoretic motivation for applying this methodology to the Schelling model, and show that it effectively rests on the presence of a potential function, suggesting a broader applicability of the methodology.

Energy required to pinch a DNA plectoneme

DNA supercoiling plays an important role on a biological point of view. One of its consequences at the supra-molecular level is the formation of DNA superhelices named plectonemes. Normally separated by a distance on the order of 10 nm, the two opposite double-strands of a DNA plectoneme must be brought closer if a protein or protein complex implicated in genetic regulation is to be bound simultaneously to both strands, as if the plectoneme was locally pinched. We propose an analytic calculation of the energetic barrier, of elastic nature, required to bring closer the two loci situated on the opposed double-strands. We examine how this energy barrier scales with the DNA supercoiling. For physically relevant values of elastic parameters and of supercoiling density, we show that the energy barrier is in the $k_{\rm B} T$ range under physiological conditions, thus demonstrating that the limiting step to loci encounter is more likely the preceding plectoneme slithering bringing the two loci side by side.Comment: Published version (new title to conform to editorial policy

Rendements croissants et structure spatiale des salaires en France

La nouvelle économie géographique présente les « rendements croissants d’agglomération » comme une variable explicative privilégiée de la concentration spatiale de l’activité économique. Dans ce cadre théorique, ces rendements croissants découleraient d’une préférence pour la variété dans la consommation. Un des enjeux empiriques de la nouvelle économie géographique reste cependant l’estimation de leur taille. Nous cherchons à évaluer la présence de tels rendements croissants d’agglomération dans la structure spatiale des salaires français, en utilisant la méthodologie d’estimation développée pour le Royaume-Uni par Fingleton (2003). Le résultat central de notre étude est la présence statistiquement significative de rendements croissants d’agglomération sur les zones d’emploi françaises, du même ordre de grandeur que ceux trouvés par Fingleton. De plus, par rapport à l’analyse originale, nous montrons que l’analyse est peu sensible à la pondération des distances entre zones d’emploi, et que la prise en compte d’une plus grande dimension temporelle permet d’améliorer la significativité des résultats.New Economic Geography presents increasing returns to agglomeration as the central explanation behind the concentration of economic activity. Within this framework, returns to scale are caused by a preference for variety in consumption which is better satisfied by agglomeration. The estimation of the size of these effects remains, however, a standing issue in the field. The focus of this study is to investigate the presence of increasing returns to agglomeration in the French spatial structure of wages using the methodology developed in Fingleton (2003) and initially used in the UK. The central finding is the statistically significant presence of such returns to scale for France, of a size comparable to the one found for the UK in the original study. Compared to Fingleton’s original work, a further results show that the results are robust to changes in the specification of the spatial weights matrix, and that taking into account a larger time-dimension leads to an improvement of the significance and the diagnostic tests

Of Ants and Voters:Maximum Entropy Prediction of Agent-Based Models with Recruitment

Maximum entropy predictions are made for the Kirman ant model as well as the Abrams-Strogatz model of language competition, also known as the voter model. In both cases the maximum entropy methodology provides good predictions of the limiting distribution of states, as was already the case for the Schelling model of segregation. An additional contribution, the analysis of the models reveals the key role played by relative entropy and the model in controlling the time horizon of the prediction