Extending the ADM formalism to Weyl geometry

In order to treat quantum cosmology in the framework of Weyl spacetimes we take the first step of extending the Arnowitt-Deser-Misner formalism to Weyl geometry. We then obtain an expression of the curvature tensor in terms of spatial quantities by splitting spacetime in (3+1)-dimensional form. We next write the Lagrangian of the gravitation field based in Weyl-type gravity theory. We extend the general relativistic formalism in such a way that it can be applied to investigate the quantum cosmology of models whose spacetimes are endowed with a Weyl geometrical structure.Comment: 10 page

Certificate Transparency with Enhancements and Short Proofs

Browsers can detect malicious websites that are provisioned with forged or fake TLS/SSL certificates. However, they are not so good at detecting malicious websites if they are provisioned with mistakenly issued certificates or certificates that have been issued by a compromised certificate authority. Google proposed certificate transparency which is an open framework to monitor and audit certificates in real time. Thereafter, a few other certificate transparency schemes have been proposed which can even handle revocation. All currently known constructions use Merkle hash trees and have proof size logarithmic in the number of certificates/domain owners. We present a new certificate transparency scheme with short (constant size) proofs. Our construction makes use of dynamic bilinear-map accumulators. The scheme has many desirable properties like efficient revocation, low verification cost and update costs comparable to the existing schemes. We provide proofs of security and evaluate the performance of our scheme.Comment: A preliminary version of the paper was published in ACISP 201

A design framework for enabling sustainability in the clothing sector

This article discusses general strategies to enable environmental sustainability within the clothing sector, providing a framework for decision makers involved in the development of programs and policies for this sector. It initially revises the environmental impact of the clothing system and determines its key environmental sustainability priorities. The framework involves five evolutionary strategies for enabling sustainable consumption and production: 1) environmental improvement of flows throughout the supply chain; 2) environmental redesign of existing clothes; 3) design of new clothes intrinsically more sustainable; 4) design of cloth-service systems and 5) promoting life styles towards sufficient consumption. The practical implications of each strategy is analysed based on correspondent ex-post-facto case studies identified in Brazil, using data collected through literature review and desktop research

100 anos de (im)permanência de Euclides da Cunha: Amazônia e Nordeste.

O trabalho investiga o pensamento de Euclides da Cunha sobre a mão-de-obra dos nordestinos dos sertões empregada nos seringais amazônicos. Segundo Cunha (1966) “O sertanejo emigrante realiza uma anomalia sobre a qual nunca é demasiado insistir: é o homem que trabalha para escravizar-se. Enquanto o colono italiano se desloca de Gênova a mais remota fazenda de São Paulo, paternalmente assistido pelos nossos poderes públicos, o cearense efetua, à sua custa, desamparado, uma viagem mais difícil, em que os adiantamentos feitos pelos contratadores insaciáveis, inçados de parcelas fantásticas e de preços inauditos, o transformam as mais das vezes em devedor para sempre insolvente”. O recurso metodológico se baseia na análise da migração nordestina para a Região Norte, Amazônia, como fonte de mão-de-obra empregada na cultura da seringueira (Hevea brasiliensis) e pesquisa bibliográfica para seleção de citações e pensamentos euclidianos sobre a temática em foco. No Nordeste, a imagem dos latifúndios litorâneos, com imensos canaviais e, também, a aridez das terras sem água dos sertões. Em contraste, a ilusão, na Amazônia, de uma vida menos árdua nos campos de seringais, que na prática, significou o regime de semi-escravidão dos sertanejos. Segundo Rabello (1983): “Não é para admirar que a Amazônia fosse, uma outra Canaã para as populações flageladas do Nordeste. Mas o que esperava o emigrante sertanejo estava longe de corresponder ao seu sonho. A Amazônia era mesmo uma miragem para os que alugavam os braços nos seringais”. Na prática, o emprego dos sertanejos nos seringais ocorreu em condições desumanas, pouca alimentação, doenças e, principalmente, o desaparecimento dos sonhos de fortuna e bem-aventurança. Nesse contexto, desmistificando a colonização da Amazônia pelos homens dos Sertões, Euclides da Cunha revela a realidade socioeconômica brasileira

Fast emergency paths schema to overcome transient link failures in ospf routing

A reliable network infrastructure must be able to sustain traffic flows, even when a failure occurs and changes the network topology. During the occurrence of a failure, routing protocols, like OSPF, take from hundreds of milliseconds to various seconds in order to converge. During this convergence period, packets might traverse a longer path or even a loop. An even worse transient behaviour is that packets are dropped even though destinations are reachable. In this context, this paper describes a proactive fast rerouting approach, named Fast Emergency Paths Schema (FEP-S), to overcome problems originating from transient link failures in OSPF routing. Extensive experiments were done using several network topologies with different dimensionality degrees. Results show that the recovery paths, obtained by FEPS, are shorter than those from other rerouting approaches and can improve the network reliability by reducing the packet loss rate during the routing protocols convergence caused by a failure.Comment: 18 page

Heat flow in the postquasistatic approximation

We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model which corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model which corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.Comment: 5 pages, 5 figure