The Gravitational and Electrostatic Fields Far from an Isolated Einstein-Maxwell Source

The exterior solution for an arbitrary charged, massive source, is studied as a static deviation from the Reissner-Nordstr\o m metric. This is reduced to two coupled ordinary differential equations for the gravitational and electrostatic potential functions. The homogeneous equations are explicitly solved in the particular case $q^2=m^2$, obtaining a multipole expansion with radial hypergeometric dependence for both potentials. In the limiting case of a neutral source, the equations are shown to coincide with recent results by Bondi and Rindler.Comment: 11 pages, revTe

Measurement errors in body size of sea scallops (Placopecten magellanicus) and their effect on stock assessment models

Body-size measurement errors are usually ignored in stock assessments, but may be important when body-size data (e.g., from visual sur veys) are imprecise. We used experiments and models to quantify measurement errors and their effects on assessment models for sea scallops (Placopecten magellanicus). Errors in size data obscured modes from strong year classes and increased frequency and size of the largest and smallest sizes, potentially biasing growth, mortality, and biomass estimates. Modeling techniques for errors in age data proved useful for errors in size data. In terms of a goodness of model fit to the assessment data, it was more important to accommodate variance than bias. Models that accommodated size errors fitted size data substantially better. We recommend experimental quantification of errors along with a modeling approach that accommodates measurement errors because a direct algebraic approach was not robust and because error parameters were diff icult to estimate in our assessment model. The importance of measurement errors depends on many factors and should be evaluated on a case by case basis

Avances en la investigación de la relación patogeno-hospedante y de la resistencia genética a enfermedades de la caña de azúcar en Argentina

Esta contribución presenta avances en la investigación de la variabilidad y resistencia genética con relación a “Roya marrón” y “Estría roja” de la caña de azúcar en Argentina. Resultados experimentales de la inoculación con roya en condiciones controladas permitieron postular que tanto la actividad peroxidasa basal como la tasa de su crecimiento con posterioridad a la infección serían mecanismos complementarios que favorecen la expresión de la resistencia a la enfermedad. También se investigó la diversidad molecular en poblaciones de roya con base en 538 marcadores AFLP a partir de muestreos en diferentes variedades y en una amplia faja de distribución de la enfermedad en el NOA. No se detectaron estructuras genéticas diferenciadas según orígenes, comportándose las diferentes poblaciones como una única gran población indiferenciada de uredosporos con alto grado de variabilidad genética intrínseca. Con relación a Estría roja se logró optimizar una técnica efectiva para el aislamiento, identificación y caracterización genética del agente responsable de la enfermedad. Los resultados obtenidos permitieron confirmar que Acidovorax avenae es el agente responsable de estría roja de la caña de azúcar en Argentina, siendo ésta la primera caracterización realizada en la región cañera para esta patología. Por otra parte el análisis de perfiles de REP-PCR y RAPD confirmó la presencia de al menos cuatro biotipos de la enfermedad en aislados de Salta y Tucumán. La existencia de diversidad genética entre aislamientos permite diseñar estrategias de control mediante el uso de variedades resistentes.The paper presents recent progress in the investigation of variability and genetic resistance in relation to Rust and Red stripe diseases of sugar cane in Argentina. Experimental results for rust innoculation under controlled conditions served to postulate that both basal peroxidase activity and its rate of increase after innoculation with the disease could be complementary mechanisms in the expression of resistance in different cultivars. Molecular diversity of rust populations collected in the field in North West Argentina were also investigated based on 538 AFLP markers. Samples collected in different varieties and sites indicated that rust uredospores populations correspond with a single mixed undifferentiated population with a high degree of intrinsic genetic variability. In regard to Red stripe it was possible to optimize an effective procedure for the isolation, identification and genetic characterization of the disease agent. Results permitted for the first time the identification of Acidovorax avenae as the agent responsible for the disease in Argentina. The profile analysis for REP-PC and RAPD indicated the presence of at least four different biotypes of the disease in Salta and Tucumán. The occurrence of genetic diversity among isolates permits the design of strategies for the control of the disease by means of resistant varieties.Fil: Mariotti, Jorge Alberto. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Machado Assefh, Cristina Renata. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta; ArgentinaFil: Rech, G.. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Fontana, P. D.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Collavino, N. G.. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Pocoví, M. I.. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Rago, A. M.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Daz, Mirta Elizabeth. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta; Argentin

Compact anisotropic spheres with prescribed energy density

New exact interior solutions to the Einstein field equations for anisotropic spheres are found. We utilise a procedure that necessitates a choice for the energy density and the radial pressure. This class contains the constant density model of Maharaj and Maartens (Gen. Rel. Grav., Vol 21, 899-905, 1989) and the variable density model of Gokhroo and Mehra (Gen. Rel. Grav., Vol 26, 75-84, 1994) as special cases. These anisotropic spheres match smoothly to the Schwarzschild exterior and gravitational potentials are well behaved in the interior. A graphical analysis of the matter variables is performed which points to a physically reasonable matter distribution.Comment: 22 pages, 3 figures, to appear in Gen. Rel. Gra

Curvature singularity of the distributional BTZ black hole geometry

For the non-rotating BTZ black hole, the distributional curvature tensor field is found. It is shown to have singular parts proportional to a $\delta$-distribution with support at the origin. This singularity is related, through Einstein field equations, to a point source. Coordinate invariance and independence on the choice of differentiable structure of the results are addressed.Comment: Latex, 7 page

A realization theorem for almost Dedekind domains

An integral domain D is called an SP-domain if every ideal is a product of radical ideals. Such domains are always almost Dedekind domains, but not every almost Dedekind domain is an SP-domain. The SP-rank of D provides a natural measure of the deviation of D from being an SP-domain. In the present paper we show that every ordinal number (Formula presented.) can be realized as the SP-rank of an almost Dedekind domain

The Ramification Tree and Almost Dedekind Domains of Prescribed SP-Rank

Given a valuation [Formula Presented] and a chain [Formula Presented] of finite extensions of [Formula Presented], we construct a weighted tree [Formula Presented] encoding information about the ramification of [Formula Presented] in the extensions [Formula Presented]; conversely, when [Formula Presented] is a discrete valuation, we show that a weighted tree [Formula Presented] can be expressed as [Formula Presented] under some mild hypotheses on [Formula Presented] or on [Formula Presented]. We use this correspondence to construct, for every countable successor ordinal number [Formula Presented] and every discrete valuation ring V, an almost Dedekind domain D integral over V whose SP-rank is [Formula Presented]. Subsequently, we extend this result to countable limit ordinal numbers by considering integral extensions of Dedekind domains with countably many maximal ideals

Glueball masses in the large N limit

The lowest-lying glueball masses are computed in SU($N$) gauge theory on a spacetime lattice for constant value of the lattice spacing $a$ and for $N$ ranging from 3 to 8. The lattice spacing is fixed using the deconfinement temperature at temporal extension of the lattice $N_T = 6$. The calculation is conducted employing in each channel a variational ansatz performed on a large basis of operators that includes also torelon and (for the lightest states) scattering trial functions. This basis is constructed using an automatic algorithm that allows us to build operators of any size and shape in any irreducible representation of the cubic group. A good signal is extracted for the ground state and the first excitation in several symmetry channels. It is shown that all the observed states are well described by their large $N$ values, with modest ${\cal O}(1/N^2)$ corrections. In addition spurious states are identified that couple to torelon and scattering operators. As a byproduct of our calculation, the critical couplings for the deconfinement phase transition for N=5 and N=7 and temporal extension of the lattice $N_T=6$ are determined.Comment: 1+36 pages, 22 tables, 21 figures. Typos corrected, conclusions unchanged, matches the published versio

Towards the glueball spectrum from unquenched lattice QCD

We use a variational technique to study heavy glueballs on gauge configurations generated with 2+1 flavours of ASQTAD improved staggered fermions. The variational technique includes glueball scattering states. The measurements were made using 2150 configurations at 0.092 fm with a pion mass of 360 MeV. We report masses for 10 glueball states. We discuss the prospects for unquenched lattice QCD calculations of the oddballs.Comment: 19 pages, 4 tables and 8 figures. One figure added. Now matches the published versio

ArguCast: a system for online multi-forecasting with gradual argumentation

Judgmental forecasting is a form of forecasting which employs (human) users to make predictions about specied future events. Judgmental forecasting has been shown to perform better than quantitative methods for forecasting, e.g. when historical data is unavailable or causal reasoning is needed. However, it has a number of limitations, arising from users’ irrationality and cognitive biases. To mitigate against these phenomena, we leverage on computational argumentation, a eld which excels in the representation and resolution of conicting knowledge and human-like reasoning, and propose novel ArguCast frameworks (ACFs) and the novel online system ArguCast, integrating ACFs. ACFs and ArguCast accommodate multi-forecasting, by allowing multiple users to debate on multiple forecasting predictions simultaneously, each potentially admitting multiple outcomes. Finally, we propose a novel notion of user rationality in ACFs based on votes on arguments in ACFs, allowing the ltering out of irrational opinions before obtaining group forecasting predictions by means commonly used in judgmental forecasting