Equivalence between two-dimensional alternating/random Ising model and the ground state of one-dimensional alternating/random XY chain

It is derived that the two-dimensional Ising model with alternating/random interactions and with periodic/free boundary conditions is equivalent to the ground state of the one-dimensional alternating/random XY model with the corresponding periodic/free boundary conditions. This provides an exact equivalence between a random rectangular Ising model, in which the Griffiths-McCoy phase appears, and a random XY chain.Comment: 10 page

Protecting the Force: Reducing Combat Vehicle Accidents via Improved Organizational Processes

Despite extraordinary efforts by leaders at all levels throughout the U.S. Army, dozens of soldiers are killed each year as a result of both combat and motor vehicle accidents. The objective of this study is to look beyond the events and symptoms of accidents which normally indicate human error, and instead study the upper-level organizational processes and problems that may constitute the actual root causes of accidents. Critical to this process is identifying critical variables, establishing causality between variables, and quantifying variables that lead to both resilience against accidents and propensities for accidents. After reviewing the available literature we report on our development of a System Dynamics model, which is an analytical model of the system that allows for extensive simulation. The results of these simulations suggest that high-level decisions that balance mission rate and operations tempo with troop availability, careful management of the work-rest cycle for deployed troops, and improvement of the processes for evaluating the lessons learned from accidents, will lead to a reduction in Army combat and motor vehicle accidents

Understanding Complexity: Dynamic Analysis of Combat Vehicle Accidents

Dozens of U.S. soldiers are killed each year as a result of both combat and motor vehicle accidents. The objective of this study is to look beyond the events and symptoms of accidents which normally indicate human error, and instead study the complex and poorly understood upper-level organizational processes and problems that may constitute the actual root causes of accidents – this is particularly challenging because the causes often involve nonlinear dynamic phenomena and have behaviors that are counter-intuitive to normal human thinking, these are often called “wicked” problems. After reviewing the available literature, a System Dynamics model was created to provide an analytical model of this multifaceted system that allows for extensive simulation. The results of these simulations suggest that high-level decisions that balance mission rate and operations tempo with troop availability, careful management of the work-rest cycle for deployed troops, and improvement of the processes for evaluating the lessons learned from accidents, will lead to a reduction in Army combat and motor vehicle accidents

ゼロの多いデータの解析：負の２項回帰モデルによる傾向の過大推定

要旨あり環境リスクと統計解析 －データ基盤構築と解析－原著論

Linhas de pesquisa de História da Igreja no Brasil

This article provides an introduction to the current state of research on the History of the Catholic Church, as reflected in studies and discussions published in books and journals in Brazil, in the years 1965-2015. The last five decades have witnessed the transformation of the field, from a discipline that concerned only Catholic ecclesiastics and laity, to a plural discipline with varied modes of approach, that attracts many specialists from the human sciences.Este artículo presenta al lector el panorama actual de los estudios y de los debates publicados en Brasil, en libros o revistas especializadas, en los años de 1965 a 2015, sobre temas e líneas de investigación en Historia de la Iglesia Católica. Queda demostrado en esas pocas líneas que en estas cinco décadas el tema pasó por grandes cambios: de ser una disciplina que interesaba casi que exclusivamente a eclesiásticos y fieles católicos, a una disciplina plural en sus metodologías de abordaje, atrayendo de este modo a muchos especialistas en ciencias humanas

Spectral flow and level spacing of edge states for quantum Hall hamiltonians

We consider a non relativistic particle on the surface of a semi-infinite cylinder of circumference $L$ submitted to a perpendicular magnetic field of strength $B$ and to the potential of impurities of maximal amplitude $w$. This model is of importance in the context of the integer quantum Hall effect. In the regime of strong magnetic field or weak disorder $B>>w$ it is known that there are chiral edge states, which are localised within a few magnetic lengths close to, and extended along the boundary of the cylinder, and whose energy levels lie in the gaps of the bulk system. These energy levels have a spectral flow, uniform in $L$, as a function of a magnetic flux which threads the cylinder along its axis. Through a detailed study of this spectral flow we prove that the spacing between two consecutive levels of edge states is bounded below by $2\pi\alpha L^{-1}$ with $\alpha>0$, independent of $L$, and of the configuration of impurities. This implies that the level repulsion of the chiral edge states is much stronger than that of extended states in the usual Anderson model and their statistics cannot obey one of the Gaussian ensembles. Our analysis uses the notion of relative index between two projections and indicates that the level repulsion is connected to topological aspects of quantum Hall systems.Comment: 22 pages, no figure

Spin-1/2 Ising-Heisenberg model with the pair XYZ Heisenberg interaction and quartic Ising interactions as the exactly soluble zero-field eight-vertex model

The spin-1/2 Ising-Heisenberg model with the pair XYZ Heisenberg interaction and quartic Ising interactions is exactly solved by establishing a precise mapping relationship with the corresponding zero-field (symmetric) eight-vertex model. It is shown that the Ising-Heisenberg model with the ferromagnetic Heisenberg interaction exhibits a striking critical behavior, which manifests itself through re-entrant phase transitions as well as continuously varying critical exponents. The changes of critical exponents are in accordance with the weak universality hypothesis in spite of a peculiar singular behavior to emerge at a quantum critical point of the infinite order, which occurs at the isotropic limit of the Heisenberg interaction. On the other hand, the Ising-Heisenberg model with the antiferromagnetic Heisenberg interaction surprisingly exhibits less significant changes of both critical temperatures as well as critical exponents upon varying a strength of the exchange anisotropy in the Heisenberg interaction.Comment: 11 pages, 9 figure

PHASE, a Monte Carlo event generator for six-fermion physics at the LHC

PHASE is a new event generator dedicated to the study of Standard Model processes with six fermions in the final state at the LHC. The code is intended for analyses of vector boson scattering, Higgs search, three gauge boson production, and top physics. This first version of the program describes final states characterized by the presence of one neutrino, $pp\to 4q +l\nu_l$, at O($\alpha^6$). PHASE is based on a new iterative-adaptive multichannel technique, and employs exact leading order matrix elements. The code can generate unweighted events for any subset of all available final states. The produced parton-level events carry full information on their colour and flavour structure, enabling the evolution of the partons into fully hadronised final states. An interface to hadronization packages is provided via the Les Houches Protocol.Comment: 27 pages, Latex, 6 figure