Contiguity orders

This paper is devoted to the study of contiguity orders i.e. orders having a linear extension extension L such that all upper (or lower) cover sets are intervals of L. This new class is a strict generalization of both interval orders and N-free orders and is linearly recognizable. It is proved that computing the number of contiguity extensions is #P-complete and that the dimension of height one contiguity orders is polynomially tractable. Moreover the membership is a comparability invariant on bi-contiguity orders. Finally for strong-contiguity orders the calculation of the dimension is NP-complete

Non-abelian Eikonals

A functional formulation and partial solution is given of the non-abelian eikonal problem associated with the exchange of non-interacting, charged or colored bosons between a pair of fermions, in the large $s$/small $t$ limit. A simple, functional ``contiguity" prescription is devised for extracting those terms which exponentiate, and appear to generate the leading, high-energy behavior of each perturbative order of this simplest non-abelian eikonal function; the lowest non-trivial order agrees with the corresponding SU(N) perturbative amplitude, while higher-order contributions to this eikonal generate an ``effective Reggeization" of the exchanged bosons, resembling previous results for the perturbative amplitude. One exact and several approximate examples are given, including an application to self-energy radiative corrections. In particular, for this class of graphs and to all orders in the coupling, we calculate the leading-log eikonal for SU(2). Based on this result, we conjecture the form of the eikonal scattering amplitude for SU(N).Comment: 19 pages, late

R\'enyi Divergence and Kullback-Leibler Divergence

R\'enyi divergence is related to R\'enyi entropy much like Kullback-Leibler divergence is related to Shannon's entropy, and comes up in many settings. It was introduced by R\'enyi as a measure of information that satisfies almost the same axioms as Kullback-Leibler divergence, and depends on a parameter that is called its order. In particular, the R\'enyi divergence of order 1 equals the Kullback-Leibler divergence. We review and extend the most important properties of R\'enyi divergence and Kullback-Leibler divergence, including convexity, continuity, limits of $\sigma$-algebras and the relation of the special order 0 to the Gaussian dichotomy and contiguity. We also show how to generalize the Pythagorean inequality to orders different from 1, and we extend the known equivalence between channel capacity and minimax redundancy to continuous channel inputs (for all orders) and present several other minimax results.Comment: To appear in IEEE Transactions on Information Theor

Empirical analysis of spatial location of activity: a proposal of using spatial association statistics

Based on the initial paper of Krugman (1991), several works have analysed the consequences of the integration process on the activity location. In this sense, Puga (1996) and Puga and Venables (1996) among others, have derived an inverse U-shape relationship between integration and agglomeration. In order to check this hypothesis, it is habitual to compute some of the traditional concentration indexes. However, this kind of indexes considers each region as an isolated economy, discarding links with others. Taking into account these ideas, this paper proposes the use of some spatial association tests in order to shed light on the consequences of an integration process, overcoming the limitations shown by other indexes of concentration. First, we discuss, from a theoretical point of view, the utility of these spatial econometric tools to get the goal of the paper. So, we analyse the behaviour of the spatial correlograms (global spatial autocorrelation tests for different orders of contiguity) and the local spatial association tests for some theoretical spatial distributions of the product (even distribution, core- periphery scheme, monocentral distribution with and without hierarchical distribution around the centre, etc). Then, we derive different temporal evolutions both of these correlograms and the local statistics related to possible scenarios after the integration (more concentration, more random distribution, etc). Second, we apply this analysis to the European Union case. In this sense, we compare the evolution shown by the GDP pc among the European regions during the period 1975-1992 with the theoretical distributions defined in the first part of the paper in order to know the trend of the spatial distribution of the activity after the deepening in the integration process. Keywords: Spatial association test, spatial econometrics, integration process

Extreme Scale De Novo Metagenome Assembly

Metagenome assembly is the process of transforming a set of short, overlapping, and potentially erroneous DNA segments from environmental samples into the accurate representation of the underlying microbiomes's genomes. State-of-the-art tools require big shared memory machines and cannot handle contemporary metagenome datasets that exceed Terabytes in size. In this paper, we introduce the MetaHipMer pipeline, a high-quality and high-performance metagenome assembler that employs an iterative de Bruijn graph approach. MetaHipMer leverages a specialized scaffolding algorithm that produces long scaffolds and accommodates the idiosyncrasies of metagenomes. MetaHipMer is end-to-end parallelized using the Unified Parallel C language and therefore can run seamlessly on shared and distributed-memory systems. Experimental results show that MetaHipMer matches or outperforms the state-of-the-art tools in terms of accuracy. Moreover, MetaHipMer scales efficiently to large concurrencies and is able to assemble previously intractable grand challenge metagenomes. We demonstrate the unprecedented capability of MetaHipMer by computing the first full assembly of the Twitchell Wetlands dataset, consisting of 7.5 billion reads - size 2.6 TBytes.Comment: Accepted to SC1

The Influence of Role Models on Immigrant Self-Employment: A Spatial Analysis for Switzerland

Theoretical and empirical research suggests a connection between the presence of role models and the emergence of entrepreneurs. Existing entrepreneurs may act as role models for self-employment candidates by providing successful examples. By explicitly considering the self-employment rates of the natives, which may influence locally the decisions of immigrants towards entrepreneurship, we develop a simple model that explains immigrant self-employment rates for a sample of 2,490 Swiss municipalities. In addition, we accommodate for the presence of spatial spillovers in the distribution of rates, and test a spatial autoregressive model which takes into account the average self-employment rates of immigrants living in nearby municipalities. Our evidence shows a significant (positive) effect of such spatial network effects, which are characterized by a quick distance decay, suggesting spatial spillovers at the household and social network level. Additionally, we show that local conditions and immigrant pool characteristics differ, with respect to self-employment choices, when examining separately urban and rural contexts.immigrants, self-employment, role models, Switzerland, spatial lag

The Communication Strategies Employed By Male And Female Students Of English Department Of Stain Gajah Putih Takengon

In an educational world, communication is seen as a necessity,as education is a communication process. When communicating, the EFL students often face many obstacles that make them use communication strategies. However, in the same time, theyare required to use the appropriate strategies, as the use of communication strategies contribute to the development of their communicative competence.There are several factors affecting the use of communication strategies by the EFL learners,one of them is gender. Communication between men and women in the classroom is considered as cross-cultural which potentially causes communication breakdown. Pertaining to this problem, this study was conducted to provide answers about the types of communication strategies used by male and female students to overcome their communication problems, and revealing the reasons why they used the strategies. The investigation is based on Bailystock (1990) classification of communication strategies. The study employed a qualitative research design. The subjects were the students who enrolled in Speaking IVcourse of the English Department of STAIN Gajah Putih Takengon. The data were collected through communication tasks (oral presentations), observations, interviews and video recordings. The findings showed that the male and female subjects used L1-based and L2-based communication strategies. Male subjects used mostly the L1-based communication strategies, meanwhile the female subjects dominantly employed the L-2 based communication strategies.The findings also indicated that the male subjects used more L1-based strategiesto help them reaching the communication goal rather than the communicationeffectiveness. In contrast, female subjects dominantly used L2-based strategies to communicate effectively.To sum up, the subjects still used the strategies, which are not beneficial to the development of their communicative competence. Therefore, these findings finally leads to a suggestion thatthe teachers should consider introducing the appropriate communication strategies to make students communicate effectively by incorporating them in the teaching and learning through the classroom activities