Fermions in the pseudoparticle approach

The pseudoparticle approach is a numerical technique to compute path integrals without discretizing spacetime. The basic idea is to integrate over those field configurations, which can be represented by a sum of a fixed number of localized building blocks (pseudoparticles). In a couple of previous papers we have successfully applied the pseudoparticle approach to pure SU(2) Yang-Mills theory. In this work we discuss how to incorporate fermionic fields in the pseudoparticle approach. To test our method, we compute the phase diagram of the 1+1-dimensional Gross-Neveu model in the large-N limit.Comment: 11 pages, 10 figure

Global Hypoellipticity for Strongly Invariant Operators

In this note, by analyzing the behavior at infinity of the matrix symbol of an invariant operator $P$ with respect to a fixed elliptic operator, we obtain a necessary and sufficient condition to guarantee that $P$ is globally hypoelliptic. We also investigate relations between the global hypoellipticity of $P$ and global subelliptic estimates.Comment: 20 page

Are Genetically Robust Regulatory Networks Dynamically Different from Random Ones?

We study a genetic regulatory network model developed to demonstrate that genetic robustness can evolve through stabilizing selection for optimal phenotypes. We report preliminary results on whether such selection could result in a reorganization of the state space of the system. For the chosen parameters, the evolution moves the system slightly toward the more ordered part of the phase diagram. We also find that strong memory effects cause the Derrida annealed approximation to give erroneous predictions about the model's phase diagram.Comment: To be published in Computer Simulation Studies in Condensed-Matter Physics XX. Ed. by D.P. Landau, S. P. Lewis, H.-B. Schuttler (Springer-Verlag, Berlin Heidelberg New York

On properties of (weakly) small groups

A group is small if it has countably many complete $n$-types over the empty set for each natural number n. More generally, a group $G$ is weakly small if it has countably many complete 1-types over every finite subset of G. We show here that in a weakly small group, subgroups which are definable with parameters lying in a finitely generated algebraic closure satisfy the descending chain conditions for their traces in any finitely generated algebraic closure. An infinite weakly small group has an infinite abelian subgroup, which may not be definable. A small nilpotent group is the central product of a definable divisible group with a definable one of bounded exponent. In a group with simple theory, any set of pairwise commuting elements is contained in a definable finite-by-abelian subgroup. First corollary : a weakly small group with simple theory has an infinite definable finite-by-abelian subgoup. Secondly, in a group with simple theory, a normal solvable group A of derived length n is contained in an A-definable almost solvable group of class n

Aid and Universal Primary Education

Universal Primary Education (UPE) is one of the main objectives of development aid. However, very little empirical evidence of its effectiveness actually exists. Until very recently, the quality of available data was not sufficient to obtain robust results regarding the relationship between international aid and educational achievements. In this article, the latest, more disaggregated and more reliable data is used to study the relationship between aid to education and educational achievements. The focus here not only on educational variables in term of coverage, but also in term of equity and process. The year of Fast Track Initiative (FTI) endorsement is used as an original instrument to tackle the endogeneity problem of aid. Our results are very robust and indicate that aid to primary education has a strong effect on primary school enrollment and gender parity. A negative impact on repetitions rate is also indicated while no effect on the pupil teacher ratio can be observed. Diminishing return in the effectiveness of aid to primary education may also be highlighted. Finally, the governance variables do not appear to have an impact on this relationship.aid effectiveness, education, Sector-specific aid

Single-Inclusive Hadron Production in Polarized pp Scattering at Next-to-Leading Logarithmic Accuracy

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process pp-> h X at high transverse momentum of the hadron h, when the initial protons are longitudinally polarized. We perform the resummation to next-to-leading logarithmic accuracy. We present numerical results for center-of-mass energies of 19.4 GeV, relevant for comparisons to data from the Fermilab E704 experiment, and 62.4 GeV, where preliminary data from RHIC have recently become available. We find significant enhancements of the spin-dependent cross sections, but a decrease of the double-spin asymmetry for the process. This effect is less pronounced at the higher energy.Comment: 18 pages, 5 figures. Figures 3, 4 and 5 modifie