Monopoles, vortices and kinks in the framework of non-commutative geometry

Non-commutative differential geometry allows a scalar field to be regarded as a gauge connection, albeit on a discrete space. We explain how the underlying gauge principle corresponds to the independence of physics on the choice of vacuum state, should it be non-unique. A consequence is that Yang-Mills-Higgs theory can be reformulated as a generalised Yang-Mills gauge theory on Euclidean space with a $Z_2$ internal structure. By extending the Hodge star operation to this non-commutative space, we are able to define the notion of self-duality of the gauge curvature form in arbitrary dimensions. It turns out that BPS monopoles, critically coupled vortices, and kinks are all self-dual solutions in their respective dimensions. We then prove, within this unified formalism, that static soliton solutions to the Yang-Mills-Higgs system exist only in one, two and three spatial dimensions.Comment: 28 pages, Late

Bounds on negative energy densities in static space-times

Certain exotic phenomena in general relativity, such as backward time travel, appear to require the presence of matter with negative energy. While quantum fields are a possible source of negative energy densities, there are lower bounds - known as quantum inequalities - that constrain their duration and magnitude. In this paper, we derive new quantum inequalities for scalar fields in static space-times, as measured by static observers with a choice of sampling function. Unlike those previously derived by Pfenning and Ford, our results do not assume any specific sampling function. We then calculate these bounds in static three- and four-dimensional Robertson-Walker universes, the de Sitter universe, and the Schwarzschild black hole. In each case, the new inequality is stronger than that of Pfenning and Ford for their particular choice of sampling function.Comment: 22 pages, 5 figures; LaTeX; minor changes mad

A Distance-Based Test of Association Between Paired Heterogeneous Genomic Data

Due to rapid technological advances, a wide range of different measurements can be obtained from a given biological sample including single nucleotide polymorphisms, copy number variation, gene expression levels, DNA methylation and proteomic profiles. Each of these distinct measurements provides the means to characterize a certain aspect of biological diversity, and a fundamental problem of broad interest concerns the discovery of shared patterns of variation across different data types. Such data types are heterogeneous in the sense that they represent measurements taken at very different scales or described by very different data structures. We propose a distance-based statistical test, the generalized RV (GRV) test, to assess whether there is a common and non-random pattern of variability between paired biological measurements obtained from the same random sample. The measurements enter the test through distance measures which can be chosen to capture particular aspects of the data. An approximate null distribution is proposed to compute p-values in closed-form and without the need to perform costly Monte Carlo permutation procedures. Compared to the classical Mantel test for association between distance matrices, the GRV test has been found to be more powerful in a number of simulation settings. We also report on an application of the GRV test to detect biological pathways in which genetic variability is associated to variation in gene expression levels in ovarian cancer samples, and present results obtained from two independent cohorts

Heterogeneous and homogeneous effects in the thermal cracking of hydrocarbons

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Monetary Policy Rules For Manging Aid Surges In Africa

We examine the properties of alternative monetary policy rules in response to large aid surges in low-income countries characterized by incomplete capital market integration and currency substitution. Using a dynamic stochastic general equilibrium model, we show that simple monetary rules that stabilize the path of expected future seigniorage for a given aid flow have attractive properties relative to a range of conventional alternatives including those involving heavy reliance on bond sterilization or a commitment to a pure exchange rate float. These simple rules, which are shown to be robust across a range of fiscal responses to aid inflows, appear to be consistent with actual responses to recent aid surges in a range of post-stabilization countries in Sub-Saharan Africa.Basle Committee, capital adequacy, financial governance, financial architecture, financial reform, international standards, capital flows, poor countries, cost of capital, international development

Nonhuman Primate Models of Respiratory Disease: Past, Present, and Future.

The respiratory system consists of an integrated network of organs and structures that primarily function for gas exchange. In mammals, oxygen and carbon dioxide are transmitted through a complex respiratory tract, consisting of the nasal passages, pharynx, larynx, and lung. Exposure to ambient air throughout the lifespan imposes vulnerability of the respiratory system to environmental challenges that can contribute toward development of disease. The importance of the respiratory system to human health is supported by statistics from the Centers for Disease Control and Prevention; in 2015, chronic lower respiratory diseases were the third leading cause of death in the United States. In light of the significant mortality associated with respiratory conditions that afflict all ages of the human population, this review will focus on basic and preclinical research conducted in nonhuman primate models of respiratory disease. In comparison with other laboratory animals, the nonhuman primate lung most closely resembles the human lung in structure, physiology, and mucosal immune mechanisms. Studies defining the influence of inhaled microbes, pollutants, or allergens on the nonhuman primate lung have provided insight on disease pathogenesis, with the potential for elucidation of molecular targets leading to new treatment modalities. Vaccine trials in nonhuman primates have been crucial for confirmation of safety and protective efficacy against infectious diseases of the lung in a laboratory animal model that recapitulates pathology observed in humans. In looking to the future, nonhuman primate models of respiratory diseases will continue to be instrumental for translating biomedical research for improvement of human health

Aid volatility, monetary policy rules and the capital account in African economies

We examine the properties of simple quantity-based monetary policy rules of the kind widely used in low-income African economies. Using a DSGE model and focusing our attention on responses to positive aid shocks, we suggest that policy rules involving substantial reserve accumulation in the face of aid surges serve to ease macroeconomic adjustment to shocks, particularly when a portion of aid is used to support fiscal adjustment. These rules are robust to assumptions about the degree of integration of the domestic public debt market with world capital markets. Although an open capital account facilitates smoother adjustment to temporary aid surges when an aid inflow is fully spent, it exacerbates the adjustment problem when aid is accompanied by fiscal adjustment and hence reinforces the case for a managed float in such circumstances.Monetary policy, Africa, Aid volatility, foreign capital flows, stochastic simulation models