Microscopic Theory for Long Range Spatial Correlations in Lattice Gas Automata

Lattice gas automata with collision rules that violate the conditions of semi-detailed-balance exhibit algebraic decay of equal time spatial correlations between fluctuations of conserved densities. This is shown on the basis of a systematic microscopic theory. Analytical expressions for the dominant long range behavior of correlation functions are derived using kinetic theory. We discuss a model of interacting random walkers with x-y anisotropy whose pair correlation function decays as 1/r^2, and an isotropic fluid-type model with momentum correlations decaying as 1/r^2. The pair correlation function for an interacting random walker model with interactions satisfying all symmetries of the square lattice is shown to have 1/r^4 density correlations. Theoretical predictions for the amplitude of the algebraic tails are compared with the results of computer simulations.Comment: 31 pages, 2 figures, final version as publishe

Imperialism’s Stepchild: Dura-Europos and the Political Uses of Archaeology in the French Mandate of Syria, 1920–1939

During the time of the French mandate in Syria in the 1920s and 1930s, both French government officials and Syrian nationalists fought to establish competing claims of political legitimacy by using the country’s archaeological sites and ancient history. French government officials — and the Western archaeologists they worked with — used archaeological sites like Dura-Europos and Palmyra to control space and to give a justification for the mission civilisatrice to French and other foreign audiences. This approach alienated many Syrian audiences in the early years of the mandate, leading to the occasional destruction of ancient artifacts. In the mandate’s second decade, Syrian nationalists began to insist on local sovereignty over archaeology, thereby using ancient history as a way to bring together Syrians across social divides and to legitimize their struggle for a political unit encompassing all of Greater Syria. But they were often undermined by the opposing rhetoric of Arab nationalists and the rigidity of French institutions, and so Syrian nationalists ended up unable to assert indigenous control over archaeology to the same extent as in neighboring countries like Iraq, which had greater local sovereignty and a more coherent nationalist ideology

Mean-field analysis of a dynamical phase transition in a cellular automaton model for collective motion

A cellular automaton model is presented for random walkers with biologically motivated interactions favoring local alignment and leading to collective motion or swarming behavior. The degree of alignment is controlled by a sensitivity parameter, and a dynamical phase transition exhibiting spontaneous breaking of rotational symmetry occurs at a critical parameter value. The model is analyzed using nonequilibrium mean field theory: Dispersion relations for the critical modes are derived, and a phase diagram is constructed. Mean field predictions for the two critical exponents describing the phase transition as a function of sensitivity and density are obtained analytically.Comment: 4 pages, 4 figures, final version as publishe

Identifying the genetic determinants of transcription factor activity

Genome-wide messenger RNA expression levels are highly heritable. However, the molecular mechanisms underlying this heritability are poorly understood.The influence of trans-acting polymorphisms is often mediated by changes in the regulatory activity of one or more sequence-specific transcription factors (TFs). We use a method that exploits prior information about the DNA-binding specificity of each TF to estimate its genotype-specific regulatory activity. To this end, we perform linear regression of genotype-specific differential mRNA expression on TF-specific promoter-binding affinity.Treating inferred TF activity as a quantitative trait and mapping it across a panel of segregants from an experimental genetic cross allows us to identify trans-acting loci (‘aQTLs') whose allelic variation modulates the TF. A few of these aQTL regions contain the gene encoding the TF itself; several others contain a gene whose protein product is known to interact with the TF.Our method is strictly causal, as it only uses sequence-based features as predictors. Application to budding yeast demonstrates a dramatic increase in statistical power, compared with existing methods, to detect locus-TF associations and trans-acting loci. Our aQTL mapping strategy also succeeds in mouse

Renormalized Equilibria of a Schloegl Model Lattice Gas

A lattice gas model for Schloegl's second chemical reaction is described and analyzed. Because the lattice gas does not obey a semi-detailed-balance condition, the equilibria are non-Gibbsian. In spite of this, a self-consistent set of equations for the exact homogeneous equilibria are described, using a generalized cluster-expansion scheme. These equations are solved in the two-particle BBGKY approximation, and the results are compared to numerical experiment. It is found that this approximation describes the equilibria far more accurately than the Boltzmann approximation. It is also found, however, that spurious solutions to the equilibrium equations appear which can only be removed by including effects due to three-particle correlations.Comment: 21 pages, REVTe

Feminism and the welfare state: on gender and individualism in The Netherlands

Past research project

Hoe moeten we bijzondere context van publiek leiderschap zien?

The politics and administration of institutional chang