Approximate performability and dependability analysis using generalized stochastic Petri Nets

Since current day fault-tolerant and distributed computer and communication systems tend to be large and complex, their corresponding performability models will suffer from the same characteristics. Therefore, calculating performability measures from these models is a difficult and time-consuming task.\ud \ud To alleviate the largeness and complexity problem to some extent we use generalized stochastic Petri nets to describe to models and to automatically generate the underlying Markov reward models. Still however, many models cannot be solved with the current numerical techniques, although they are conveniently and often compactly described.\ud \ud In this paper we discuss two heuristic state space truncation techniques that allow us to obtain very good approximations for the steady-state performability while only assessing a few percent of the states of the untruncated model. For a class of reversible models we derive explicit lower and upper bounds on the exact steady-state performability. For a much wider class of models a truncation theorem exists that allows one to obtain bounds for the error made in the truncation. We discuss this theorem in the context of approximate performability models and comment on its applicability. For all the proposed truncation techniques we present examples showing their usefulness

Negotiating belonging and place: an exploration of mestiza women’s everyday resistance in Cajamarca, Peru.

Since 1993, the Cajamarca region of Peru has been home to the Yanacocha gold mine, associated with environmental degradation, negative health impacts, and socio-economic consequences. In 2012, large-scale protests broke out across the region over the newly proposed Conga mine. Increasingly, scholarship is devoted to recognizing socio-environmental struggles outside of mass-mobilization and public protests; at the local, household and everyday level, often performed over much longer timescales. In this context, I critically explore the everyday resistance of mestiza-identifying women in Cajamarca city. Through a discussion of how their on-going resistance critically constructs who/what belongs in place, and who/what is ‘other’/‘stranger’, I analyse how they mobilise gendered local values and knowledge to continue opposing large-scale mining in the aftermath of the Conga conflict

Which FLRW comoving 3-manifold is preferred observationally and theoretically?

The lack of structure greater than 10 Gpc/h in Wilkinson Microwave Anisotropy Probe (WMAP) observations of the cosmic microwave background (CMB) favours compact Friedmann-Lemaitre-Robertson-Walker (FLRW) models of the Universe. The present best candidates based on observations are the Poincare dodecahedral space S^3/I^* and the 3-torus T^3. The residual gravity effect favours the Poincare space, while a measure space argument where the density parameter is a derived parameter favours flat spaces almost surely.Comment: 3 pages, Twelfth Marcel Grossmann Meeting on General Relativity, ed. Thibault Damour, Robert T Jantzen, Remo Ruffini, Singapore: World Scientifi

Topological acceleration in relativistic cosmology

Heuristic approaches in cosmology bypass more difficult calculations that would more strictly agree with the standard Einstein equation. These give us the well-known Friedmann-Lemaitre-Robertson-Walker (FLRW) models, and, more recently, the feedback effect of the global topology of spatial sections on the acceleration of test particles. Forcing the FLRW heuristic model on observations leads to dark energy, which, pending fully relativistic calculations, is best interpreted as an artefact. Could topological acceleration also be an artefact of using a heuristic approach? A multiply connected exact solution of the Einstein equation shows that topological acceleration is present in at least one fully relativistic case---it is not an artefact of Newtonian-like thinking.Comment: 4 pages, 1 figure, Multiverse and Fundamental Cosmology Conference, 10-14 September, 2012, Szczecin, Polan