Sum Rule for the ADM Mass and Tensions in Planar AdS Spacetimes

An asymptotically planar AdS spacetimes is characterized by its ADM mass and tensions. We define an additional ADM charge Q associated with the scaling Killing vector of AdS, show that Q is given by a certain sum over the ADM mass and tensions and that Q vanishes on solutions to the Einstein equation with negative cosmological constant. The sum rule for the mass and tensions thus established corresponds in an AdS/CFT context to the vanishing of the trace of the boundary stress tensor. We also show that an analogous sum rule holds for local planar sources of stress-energy sources in AdS. In a simple model consisting of a static, plane symmetric source we find that the perturbative stress-energy tensor must be tracefree.Comment: 15 pages; v2 minor change

Gravitational Tension and Thermodynamics of Planar AdS Spacetimes

We derive new thermodynamic relations for asymptotically planar AdS black hole and soliton solutions. In addition to the ADM mass, these spacetimes are characterized by gravitational tensions in each of the planar spatial directions. We show that with planar AdS asymptotics, the sum of the ADM mass and tensions necessarily vanishes, as one would expect from the AdS /CFT correspondence. Each Killing vector of such a spacetime leads to a Smarr formula relating the ADM mass and tensions, the black hole horizon and soliton bubble areas, and a set of thermodynamic volumes that arise due to the non-vanishing cosmological constant. These Smarr relations display an interesting symmetry between black holes and bubbles, being invariant under the simultaneous interchange of the mass and black hole horizon area with the tension and soliton bubble area. This property may indicate a symmetry between the confining and deconfined phases of the dual gauge theory.Comment: 23 pages; v2 references adde

Exact Solutions in Gravity: A journey through spacetime with the Kerr-Schild ansatz

The Kerr-Schild metric ansatz can be expressed in the form g_{ab} = \gbar_{ab}+\lambda k_ak_b, where \gbar_{ab} is a background metric satisfying Einstein\u27s equations, $k_a$ is a null-vector, and $\lambda$ is a free parameter. It was discovered in 1963 while searching for the elusive rotating black hole solutions to Einstein\u27s equations, fifty years after the static solution was found and Einstein first formulated his theory of general relativity. While the ansatz has proved an excellent tool in the search for new exact solutions since then, its scope is limited, particularly with respect to higher dimensional theories. In this thesis, we present the analysis behind three possible modifications. In the first case a spacelike vector is added to the ansatz, and we show that many, although not all, of the simplifications that occur in the Kerr-Schild case continue to hold for the extended version of the ansatz. In the second case we look at the Kerr-Schild ansatz in the context of higher curvature theories of gravity; specifically Lovelock gravity which organizes terms in the Lagrangian in such a way that the theory is ghost-free and the equations of motion remain second order. We find that the field equations reduce, in a similar manner as in the Kerr-Schild case, to a single equation of order $\lambda^p$ for unique vacuum theories of order $p$ in the curvature. Finally, we investigate the role of the Kerr-Schild ansatz in the context of Kaluza-Klein gravity theories

Kerr-Schild spacetimes with (A)dS background

General properties of Kerr-Schild spacetimes with (A)dS background in arbitrary dimension are studied. It is shown that the geodetic Kerr-Schild vector k is a multiple WAND of the spacetime. Einstein Kerr-Schild spacetimes with non-expanding k are shown to be of Weyl type N, while the expanding spacetimes are of type II or D. It is shown that this class of spacetimes obeys the optical constraint. This allows us to solve Sachs equation, determine r-dependence of boost weight zero components of the Weyl tensor and discuss curvature singularities.Comment: 17 pages, minor change

An analysis of Brazilian sugarcane bagasse ash behavior under thermal gasification.

Background: Ashes from sugarcane were analyzed by X-ray fluorescence, ash content, X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). FactSage 6.4 database software was used to estimate viscosity at high temperatures (900 - 1550°C) of them. Results: The results showed that although ashes from sugarcane bagasse contain silica, most of its SiO2 is from soil contamination. Higher and lower silica samples treated at 1350°C for 20 minutes showed that the fine portion of fraction of the ashes melted at this temperature. Conclusions: The melting phase could act as sticking flux for the coarse silica particles on the gasifier bottom wall, which could compromise the gasification process

Counselling at the Workplace in Tanzania What can Distance Education do?

his paper examines practice in counselling at workplaces. It draws examples from Tanzania. Authors define counselling as a collaborative approach towards problem solving. It is a step-by-step process of self-actualization guided by a counsellor. The authors are of the view that in most workplaces in Tanzania, for instance, there is a vacuum in counselling activities. Workers have very few professional counsellors to go to for guidance and counselling. This vacuum is usually promptly filled up with managerial actions, trade unionism and personal efforts towards individualisation which is merely advice and not counselling. They further argue that, both trade unionists and managers have objectives sometimes different from those of workers. In other instances, they frustrate the workers instead of helping them to fruitful and well-informed decisions. The paper concludes that the vacuum that exists in counselling at the workplace may be damaging to some work relations, institutional services, and can be a source of job dissatisfaction and low productivity. Thus it must be replaced with professional counselling services. The paper further argues that even where professional counsellors are employed (for example educational institutions like universities), only students are counselled and the workers are not covered as if they have no problems. Counsellors have strictly prescribed duties of dealing with students only. This paper recommends that distance education can be used in various forms to train counsellors for workplaces. Both short and long term programmes meant to gloom counsellors capable of professionally guiding and counselling workers can be developed.Keywords: Counselling at the workplace, distance education, trade unionism, individuation, managerial action

Environmental screening tools for assessment of infrastructure plans based on biodiversity preservation and global warming (PEIT, Spain).

Most Strategic Environmental Assessment (SEA) research has been concerned with SEA as a procedure, and there have been relatively few developments and tests of analytical methodologies. The first stage of the SEA is the ‘screening’, which is the process whereby a decision is taken on whether or not SEA is required for a particular programme or plan. The effectiveness of screening and SEA procedures will depend on how well the assessment fits into the planning from the early stages of the decision-making process. However, it is difficult to prepare the environmental screening for an infrastructure plan involving a whole country. To be useful, such methodologies must be fast and simple. We have developed two screening tools which would make it possible to estimate promptly the overall impact an infrastructure plan might have on biodiversity and global warming for a whole country, in order to generate planning alternatives, and to determine whether or not SEA is required for a particular infrastructure plan

Liberdade de expressão e moderação de contéudo: proteção de direitos fundamentais em plataformas online

O objetivo deste trabalho é mostrar como a popularização das plataformas online impactou diretamente na liberdade de expressão das pessoas, com enfoque nas práticas de moderação de conteúdo. As plataformas online, embora possuam natureza contratual privada, mostram-se como verdadeiras praças públicas, onde pessoas, canais de mídia e instituições públicas divulgam informações e expressam opiniões. na prática, observamos que as plataformas, ao moderarem conteúdo, podem violar direitos e restringir indevidamente a liberdade de expressão das pessoas. Nesse cenário, defendemos a necessidade de o Estado assumir um papel proativo para regulamentar plataformas online e proteger a liberdade de expressão. Ademais, dada a assimetria de poder entre plataformas e usuários, bem como sua relevância equiparada à de um espaço público, argumentamos pela eficácia horizontal imediata de direitos fundamentais nesses ambientes online. Por fim, sugerimos possíveis medidas para garantir direitos e proteger a liberdade de expressão, como obrigações de transparência e respeito ao devido processo e ampla defesa por parte das plataformasThe aim of this paper is to describe how the popularization of online platforms has directly affected people's freedom of expression, focusing on content moderation practices. Although contractually private, online platforms resemble public squares, where people, companies and public institutions disclose information and express opinions. In practice, online platforms may violate users' rights and unduly restrict freedom of expression, by moderating content. In this scenario, we advocate the necessity for the State to take a proactive role in regulating online platforms and protecting freedom of expression. Moreover, considering the asymmetry of power between platforms and users, as well as their relevance as public space, we argue for the direct horizontal application of fundamental rights in these virtual environments. Finally, we suggest possible measures to safeguard and protect freedom of expression online, such as transparency obligations and respect for due process by online platform

Interpretive structural modelling of risk sources in a virtual organisation

International audienceSpeedier network decision making together with shorter time to bring items to market together with lower network operating costs all result from enhanced knowledge sharing. In addition re-use of enterprise and network knowledge resulting from improved capture means that any risk of repeating earlier project work is limited, repetition of past mistakes is reduced. Decisions are made with greater awareness of any risks involved and therefore there is likely to be a reduction in costs arising from faulty decisions and failed collaborations. While there are many advantages attaching to the use of virtual organizations (VOs) there are also challenges, including risks that have become apparent through undertaking a review of the literature. In total 13 sources of risk were found stemming from the network related risks in a VO, where the emphasis of the study was placed,. This paper contains a thorough study that will identify these threats as well as gaining a sound understanding of them by examining them one by one as they have been identified by the literature and previous studies. Subsequently, their relative importance will be analysed through the use of Structural Modeling (ISM) using information gathered in a questionnaire