Israel: Threatened From Inside and Out...

Martin Fletcher, Author, fomer NBC News Middle East Correspondent & Tel Aviv Bureau Chief.https://digitalcommons.fairfield.edu/bennettcenter-posters/1296/thumbnail.jp

A framework for deflated and augmented Krylov subspace methods

We consider deflation and augmentation techniques for accelerating the convergence of Krylov subspace methods for the solution of nonsingular linear algebraic systems. Despite some formal similarity, the two techniques are conceptually different from preconditioning. Deflation (in the sense the term is used here) "removes" certain parts from the operator making it singular, while augmentation adds a subspace to the Krylov subspace (often the one that is generated by the singular operator); in contrast, preconditioning changes the spectrum of the operator without making it singular. Deflation and augmentation have been used in a variety of methods and settings. Typically, deflation is combined with augmentation to compensate for the singularity of the operator, but both techniques can be applied separately. We introduce a framework of Krylov subspace methods that satisfy a Galerkin condition. It includes the families of orthogonal residual (OR) and minimal residual (MR) methods. We show that in this framework augmentation can be achieved either explicitly or, equivalently, implicitly by projecting the residuals appropriately and correcting the approximate solutions in a final step. We study conditions for a breakdown of the deflated methods, and we show several possibilities to avoid such breakdowns for the deflated MINRES method. Numerical experiments illustrate properties of different variants of deflated MINRES analyzed in this paper.Comment: 24 pages, 3 figure

Designing a knowledge distribution simulator

To make good decisions, we need to be suitably informed. \u27Good\u27 and \u27Suitably\u27 in this case depend on the informational needs of the decision and the mechanisms of getting the information to the decision maker in time. The trade-offs in qualities, quantities, timeliness, impacts on other activities, and so on are infamously wickedly complex, and usually buried in a clutter of special circumstances, personality characteristics, environments unsuitable for study, and so on. Decision-making systems can be explored using case studies and exercises, but these are limited by the expense and time of using real people. A virtual simulator for large scale networks of communities can provide systems to examine that are not otherwise possible, while bearing in mind that simulators only partially reflect real systems. This paper describes a design for such a simulator framework that can be implemented on an ordinary desktop computer. We intend to use it to exercise and explore various ‘knowledge distribution strategies’ in order to understand and suggest information communication mechanisms for investigation in the real world, without expecting it to be complete enough to be prescriptive. We focus on military collaborations as suitably \u27eXtreme\u27 environments to exercise these communication mechanisms. Topics for further investigation include isolation, turnover and resilience

Levels of Altruism

The phenomenon of altruism extends from the biological realm to the human socio-cultural realm. This paper sketches a coherent outline of multiple types of altruism of progressively increasing scope that span these two realms and are grounded in an ever-expanding sense of self. Discussion of this framework notes difficulties associated with altruisms at different levels. It links scientific ideas about the evolution of cooperation and about hierarchical order to perennial philosophical and religious concerns. It offers a conceptual background for inquiry into societal challenges that call for altruistic behavior, especially the challenge of environmental and social sustainability

Effect of aromatic amines on the properties of formaldehyde-based xerogels

This study investigates the synthesis of formaldehyde-based xerogels using alternative aromatic precursors, with comparison to traditional resorcinol-formaldehyde analogues, in order to alter the chemical composition of the resulting gels. By replacing resorcinol with aromatic amine molecules, i.e., ammeline, melamine and melem, each expected to undergo similar reactions with formaldehyde as the substituted species, we found that for all substituted gels, at low additive contents, the gel structure was compromised and non-porous materials were formed, as opposed to the most abundant monomers, and therefore, these additives seem to act as impurities at low levels. Working towards higher additive contents, melem monomers exhibited low solubility (~5%), even at elevated temperatures, thereby limiting the range to which melem could act as a substitute, while melamine could be incorporated up to ~40% under acidic conditions, with enhanced microporosity over this range. Pure gels were successfully synthesised from ammeline, but their performance was inferior to resorcinol-formaldehyde gels, while melamine-formaldehyde analogues required acidic reaction conditions but shrank considerably on sub-critical drying, adversely affecting the gel properties and demonstrating their lack of potential as sorbents. This demonstrates the potential for the inclusion of aminated aromatics within resorcinol-based gel systems, however, only as partial substitutes and not complete replacements

Generalized Wilson Chain for solving multichannel quantum impurity problems

The Numerical Renormalization Group is used to solve quantum impurity problems, which describe magnetic impurities in metals, nanodevices, and correlated materials within DMFT. Here we present a simple generalization of the Wilson Chain, which improves the scaling of computational cost with the number of channels/bands, bringing new problems within reach. The method is applied to calculate the t-matrix of the three-channel Kondo model at T=0, which shows universal crossovers near non-Fermi liquid critical points. A non-integrable three-impurity problem with three bands is also studied, revealing a rich phase diagram and novel screening/overscreening mechanisms.Comment: 5 pages + 5 pages supplementary materia

Unifying the Theories of Inclusive Fitness and Reciprocal Altruism

Inclusive fitness and reciprocal altruism are widely thought to be distinct explanations for how altruism evolves. Here we show that they rely on the same underlying mechanism. We demonstrate this commonality by applying Hamilton’s rule, normally associated with inclusive fitness, to two simple models of reciprocal altruism: one, an iterated prisoner’s dilemma model with conditional behavior; the other, a mutualistic symbiosis model where two interacting species differ in conditional behaviors, fitness benefits, and costs. We employ Queller’s generalization of Hamilton’s rule because the traditional version of this rule does not apply when genotype and phenotype frequencies differ or when fitness effects are nonadditive, both of which are true in classic models of reciprocal altruism. Queller’s equation is more general in that it applies to all situations covered by earlier versions of Hamilton’s rule but also handles nonadditivity, conditional behavior, and lack of genetic similarity between altruists and recipients. Our results suggest changes to standard interpretations of Hamilton’s rule that focus on kinship and indirect fitness. Despite being more than 20 years old, Queller’s generalization of Hamilton’s rule is not sufficiently appreciated, especially its implications for the unification of the theories of inclusive fitness and reciprocal altruism