Criticality and Heterogeneity in the Solution Space of Random Constraint Satisfaction Problems

Random constraint satisfaction problems are interesting model systems for spin-glasses and glassy dynamics studies. As the constraint density of such a system reaches certain threshold value, its solution space may split into extremely many clusters. In this paper we argue that this ergodicity-breaking transition is preceded by a homogeneity-breaking transition. For random K-SAT and K-XORSAT, we show that many solution communities start to form in the solution space as the constraint density reaches a critical value alpha_cm, with each community containing a set of solutions that are more similar with each other than with the outsider solutions. At alpha_cm the solution space is in a critical state. The connection of these results to the onset of dynamical heterogeneity in lattice glass models is discussed.Comment: 6 pages, 4 figures, final version as accepted by International Journal of Modern Physics

An Assessment of Civic Engagement and Educational Attainment

It is well documented that individuals with higher levels of education tend to be more civically engaged. In a two-part study conducted for the Center for Information and Research on Civic Learning and Engagement (CIRCLE), we provide empirical evidence using 1988-2000 panel data from the National Education Longitudinal Study of 1988 (NELS) that civic engagement might also promote educational attainment: civically-engaged teenagers make greater scholastic progress during high school and subsequently acquire higher levels of education than their otherwise similar peers. Our first essay provides supporting empirical evidence for this relationship in general, and the second essay broadens these findings across gender and race/ethnicity. With regards to policy relevance, the primary results point to the importance of civic participation as one means to foster both social and human capital investments. The purpose of this fact sheet is to provide highlights from our two-part study

The English-Language Proficiency of Recent Immigrants in the U.S. During the Early 1900s

Using U.S. decennial census data, we find that in 1920, immigrants (particularly those from Southern and Eastern Europe) were more likely to speak the English language within three years of migrating than their counterparts had been in either 1900 or 1910. Our results suggest that the foreign-born reacted to socioeconomic and political events by learning English before or shortly after migrating to the U.S. This study not only provides previously unknown information about immigrants’ English fluency in the early twentieth century, but it also offers empirical insight into the assimilation pressures that certain immigrant groups experienced at the time.

Superconducting transport through a vibrating molecule

Nonequilibrium electronic transport through a molecular level weakly coupled to a single coherent phonon/vibration mode has been studied for superconducting leads. The Keldysh Green function formalism is used to compute the current for the entire bias voltage range. In the subgap regime, Multiple Andreev Reflection (MAR) processes accompanied by phonon emission cause rich structure near the onset of MAR channels, including an even-odd parity effect that can be interpreted in terms of an inelastic MAR ladder picture. Thereby we establish a connection between the Keldysh formalism and the Landauer scattering approach for inelastic MAR.Comment: 5 pages, 5 figures, version contains now more details, accepted by PR

Intrinsic limitations of inverse inference in the pairwise Ising spin glass

We analyze the limits inherent to the inverse reconstruction of a pairwise Ising spin glass based on susceptibility propagation. We establish the conditions under which the susceptibility propagation algorithm is able to reconstruct the characteristics of the network given first- and second-order local observables, evaluate eventual errors due to various types of noise in the originally observed data, and discuss the scaling of the problem with the number of degrees of freedom

Poverty matters, but to what extent? : perceptions of poverty through the literary discourse in Costa Rica

Costa Rica;poverty;sociological analysis

³¹P Saturation Transfer and Phosphocreatine Imaging in the Monkey Brain

³¹P magnetic resonance imaging with chemical-shift discrimination by selective excitation has been employed to determine the phosphocreatine (PCr) distribution in the brains of three juvenile macaque monkeys. PCr images were also obtained while saturating the resonance of the {gamma}-phosphate of ATP, which allowed the investigation of the chemical exchange between PCr and the {gamma}-phosphate of ATP catalyzed by creatine kinase. Superposition of the PCr images over the proton image of the same monkey brain revealed topological variations in the distribution of PCr and creatine kinase activity. PCr images were also obtained with and without visual stimulation. In two out of four experiments, an apparently localized decrease in PCr concentration was noted in visual cortex upon visual stimulation. This result is interpreted in terms of a possible role for the local ADP concentration in stimulating the accompanying metabolic response

Reducing the size and number of linear programs in a dynamic Gr\"obner basis algorithm

The dynamic algorithm to compute a Gr\"obner basis is nearly twenty years old, yet it seems to have arrived stillborn; aside from two initial publications, there have been no published followups. One reason for this may be that, at first glance, the added overhead seems to outweigh the benefit; the algorithm must solve many linear programs with many linear constraints. This paper describes two methods of reducing the cost substantially, answering the problem effectively.Comment: 11 figures, of which half are algorithms; submitted to journal for refereeing, December 201

Buchberger-Zacharias Theory of multivariate Ore extensions

Following the recent survey on Buchberger-Zacharias Theory for monoid rings R[S] over a unitary effective ring R and an effective monoid S, we propose here a presentation of Buchberger Zacharias Theory and related Grobner basis computation algorithms for multivariate Ore extensions of rings presented as modules over a principal ideal domain, using Moller-Pritchard lifting theorem