Phase diagram of the three-dimensional Hubbard model at half filling

We investigate the phase diagram of the three-dimensional Hubbard model at half filling using quantum Monte Carlo (QMC) simulations. The antiferromagnetic Neel temperature T_N is determined from the specific heat maximum in combination with finite-size scaling of the magnetic structure factor. Our results interpolate smoothly between the asymptotic solutions for weak and strong coupling, respectively, in contrast to previous QMC simulations. The location of the metal-insulator transition in the paramagnetic phase above T_N is determined using the electronic compressibility as criterion.Comment: 6 pages, 6 figures, to be published in Eur. Phys. J. B (2000

Propositional logic with short-circuit evaluation: a non-commutative and a commutative variant

Short-circuit evaluation denotes the semantics of propositional connectives in which the second argument is evaluated only if the first argument does not suffice to determine the value of the expression. Short-circuit evaluation is widely used in programming, with sequential conjunction and disjunction as primitive connectives. We study the question which logical laws axiomatize short-circuit evaluation under the following assumptions: compound statements are evaluated from left to right, each atom (propositional variable) evaluates to either true or false, and atomic evaluations can cause a side effect. The answer to this question depends on the kind of atomic side effects that can occur and leads to different "short-circuit logics". The basic case is FSCL (free short-circuit logic), which characterizes the setting in which each atomic evaluation can cause a side effect. We recall some main results and then relate FSCL to MSCL (memorizing short-circuit logic), where in the evaluation of a compound statement, the first evaluation result of each atom is memorized. MSCL can be seen as a sequential variant of propositional logic: atomic evaluations cannot cause a side effect and the sequential connectives are not commutative. Then we relate MSCL to SSCL (static short-circuit logic), the variant of propositional logic that prescribes short-circuit evaluation with commutative sequential connectives. We present evaluation trees as an intuitive semantics for short-circuit evaluation, and simple equational axiomatizations for the short-circuit logics mentioned that use negation and the sequential connectives only.Comment: 34 pages, 6 tables. Considerable parts of the text below stem from arXiv:1206.1936, arXiv:1010.3674, and arXiv:1707.05718. Together with arXiv:1707.05718, this paper subsumes most of arXiv:1010.367

High-Quality Shared-Memory Graph Partitioning

Partitioning graphs into blocks of roughly equal size such that few edges run between blocks is a frequently needed operation in processing graphs. Recently, size, variety, and structural complexity of these networks has grown dramatically. Unfortunately, previous approaches to parallel graph partitioning have problems in this context since they often show a negative trade-off between speed and quality. We present an approach to multi-level shared-memory parallel graph partitioning that guarantees balanced solutions, shows high speed-ups for a variety of large graphs and yields very good quality independently of the number of cores used. For example, on 31 cores, our algorithm partitions our largest test instance into 16 blocks cutting less than half the number of edges than our main competitor when both algorithms are given the same amount of time. Important ingredients include parallel label propagation for both coarsening and improvement, parallel initial partitioning, a simple yet effective approach to parallel localized local search, and fast locality preserving hash tables

Inequities in the delivery of services to a female farm clientele: some implications for policy

This paper is based on data collected in 1975 from a geographically stratified sample of 212 small-scale farm households in one administrative location of Kakamega District, western Kenya. It is found that women farm managers experience a persistent and pervasive bias in the delivery of the government agricultural services to which they are entitled. The bias increases in intensity as the value of the service increases. Moreover, the bias holds under a number of different controls including economic standing, size of land holding and demonstrated interest in adopting agricultural innovations in a timely way. Despite these inequities in access to services, women farm manager in the area appear to be as productive and as willing to adopt innovations as other types of farmers. A number of suggestions are made to deal with the problem of inequity in the delivery of agricultural services

In Defense of AID

The trashing of the Agency for International Development and the public scapegoating by my sisters at the National Women\u27s Studies Association Convention is an experience which must, I feel, be noted in the annals of the conference. Recognizing that U.S. women\u27s studies programs tend to be relatively parochial, AID\u27s and, in particular, the Women in Development office\u27s concern was to bring an international development dimension, including the participation of Third World women, to the wide array of panels. On one panel— U.S. and Third World Women: What Are the Connections? —were researchers who discussed women in multinational corporations, the changing sex division of labor in agricultural economies, female-headed households, and the decolonialization of research on women. The second panel— Broadening Women\u27s Studies: Developing World Dimensions —built on the first, with participants discussing models of existing international women\u27s studies programs both inside and outside the U.S., and resources available for networking among women within and across campuses. As with all other panels, our proposal was approved by the Convention Coordinators. Both panels were well received by the attendees, partly because, as chair, I structured presentations and discussion toward content, to avoid disruption

Double beta decay versus cosmology: Majorana CP phases and nuclear matrix elements

We discuss the relation between the absolute neutrino mass scale, the effective mass measured in neutrinoless double beta decay, and the Majorana CP phases. Emphasis is placed on estimating the upper bound on the nuclear matrix element entering calculations of the double beta decay half life. Consequently, one of the Majorana CP phases can be constrained when combining the claimed evidence for neutrinoless double beta decay with the neutrino mass bound from cosmology.Comment: 11 pages, 3 figure