Legacies of a Past Modernism Discourses of Development and the Shaping of Centralized Electricity Infastructures in Late- and Postcolonial Tanzania

As the UN has declared the years 2014-2024 the “Decade of Sustainable Energy for All”, countries in Sub-Saharan Africa struggle with the transition towards more sustainable and more inclusive energy infrastructures. In many rural areas, electrification rates remain as low as 1-2%. For many countries, one of the main barriers for rural electrification is the legacy of a model of top-down planning, large-scale power generation and a centralized topology of the electricity infrastructure. Nonetheless, historiography on electricity infrastructures in Africa is nearly non-existent. At the example of Tanzania this paper shows, that the centralized power models which dominate the continent today were shaped by modernization and development discourses during the late colonial and post-independence period. Because of its particular characteristics, electricity lent itself perfectly to the goal of making development measurable — a goal which was essential to a “high modernist” vision of development, advocated by new nation states as well as international funders. The paper illustrates how large hydropower projects proved successful in expanding generation capacities and urban electrification rates, but failed in providing electricity to rural areas and created pathdependencies which have led to dead ends in the last 20 years

Residual entropy in a model for the unfolding of single polymer chains

We study the unfolding of a single polymer chain due to an external force. We use a simplified model which allows to perform all calculations in closed form without assuming a Boltzmann-Gibbs form for the equilibrium distribution. Temperature is then defined by calculating the Legendre transform of the entropy under certain constraints. The application of the model is limited to flexible polymers. It exhibits a gradual transition from compact globule to rod. The boundary line between these two phases shows reentrant behavior. This behavior is explained by the presence of residual entropy.Comment: 5 pages, 4 figures, extended version of arXiv:cond-mat/061225

Product differentiation when consumers may choose not to buy: Hotelling's convergence result revisited

Nous étudions le modèle spatial de différentiation d'Hotelling, mais au lieu de supposer que le marché est couvert quelles que soient les localisations des deux firmes, nous supposons qu'il existe une distance maximale (éventuellement infinie) qu'un consommateur est prêt à parcourir pour acheter le bien. Cette généralisation apparemment anodine des hypothèses d'Hotelling modifie complètement les résultats : le principe de "différentiation minimale" d'Hotelling n'est plus vérifié en général. A l'équilibre, les firmes s'engagent dans un processus de différentiation maximale, intermédiaire ou minimale, selon la forme de la distribution des positions des consommateurs et cette distance critique qu'un consommateur est prêt à parcourir pour acquérir le bien.

Dynamical modelling of superstatistical complex systems

We show how to construct the optimum superstatistical dynamical model for a given experimentally measured time series. For this purpose we generalise the superstatistics concept and study a Langevin equation with a memory kernel whose parameters fluctuate on a large time scale. It is shown how to construct a synthetic dynamical model with the same invariant density and correlation function as the experimental data. As a main example we apply our method to velocity time series measured in high-Reynolds number turbulent Taylor-Couette flow, but the method can be applied to many other complex systems in a similar way.Comment: 11 pages, 4 figure

Maximum entropy estimation of transition probabilities of reversible Markov chains

In this paper, we develop a general theory for the estimation of the transition probabilities of reversible Markov chains using the maximum entropy principle. A broad range of physical models can be studied within this approach. We use one-dimensional classical spin systems to illustrate the theoretical ideas. The examples studied in this paper are: the Ising model, the Potts model and the Blume-Emery-Griffiths model

Transition records of stationary Markov chains

In any Markov chain with finite state space the distribution of transition records always belongs to the exponential family. This observation is used to prove a fluctuation theorem, and to show that the dynamical entropy of a stationary Markov chain is linear in the number of steps. Three applications are discussed. A known result about entropy production is reproduced. A thermodynamic relation is derived for equilibrium systems with Metropolis dynamics. Finally, a link is made with recent results concerning a one-dimensional polymer model.Comment: corrected error in the definition of the entropy production variable and in the proof of the fluctuation theore