Extracting spacetimes using the AdS/CFT conjecture

We present analytic methods for extracting a class of bulk geometries given information of certain physical quantities in the boundary CFT. More specifically we look at singular correlators and entanglement entropy in the CFT to provide information of null and spacelike geodesics repectively in the bulk. We show that static spherically symmetric, asymptotically AdS spacetimes which do not admit null circular orbits can be fully recovered, and that any spacetime can be recovered up to the local maximum of the potential. We provide analytical and numerical examples to verify the methods used.Comment: 18 pages, 7 figure

Making Social Work Work: Improving social work for vulnerable families and children without parental care around the world: A literature review

This literature review calls for families and children in developing countries to be supported in ways that are appropriate to the conditions, culture and resources available rather than through approaches to social work that are common in the west. Children living without, or at risk of losing, parental care have wide and varied needs, this paper highlights the need for more thorough assessments of appropriate approaches, functions and support needs for social workers, and suggests elements of an assessment tool to explore these issues. This paper is the first part of a longer process for developing such an assessment tool, and plans are underway to further develop and test the tool in 2012.- See more at: http://www.everychild.org.uk/resources/reports-policies/making-social-work-work#sthash.4EF6qnzc.dpu

LQG for the Bewildered

We present a pedagogical introduction to the notions underlying the connection formulation of General Relativity - Loop Quantum Gravity (LQG) - with an emphasis on the physical aspects of the framework. We begin by reviewing General Relativity and Quantum Field Theory, to emphasise the similarities between them which establish a foundation upon which to build a theory of quantum gravity. We then explain, in a concise and clear manner, the steps leading from the Einstein-Hilbert action for gravity to the construction of the quantum states of geometry, known as \emph{spin-networks}, which provide the basis for the kinematical Hilbert space of quantum general relativity. Along the way we introduce the various associated concepts of \emph{tetrads}, \emph{spin-connection} and \emph{holonomies} which are a pre-requisite for understanding the LQG formalism. Having provided a minimal introduction to the LQG framework, we discuss its applications to the problems of black hole entropy and of quantum cosmology. A list of the most common criticisms of LQG is presented, which are then tackled one by one in order to convince the reader of the physical viability of the theory. An extensive set of appendices provide accessible introductions to several key notions such as the \emph{Peter-Weyl theorem}, \emph{duality} of differential forms and \emph{Regge calculus}, among others. The presentation is aimed at graduate students and researchers who have some familiarity with the tools of quantum mechanics and field theory and/or General Relativity, but are intimidated by the seeming technical prowess required to browse through the existing LQG literature. Our hope is to make the formalism appear a little less bewildering to the un-initiated and to help lower the barrier for entry into the field.Comment: 87 pages, 15 figures, manuscript submitted for publicatio

Profitability and Stability in International Currency Markets

A number of recent empirical studies have rejected the hypothesis that forward exchange rates are unbiased forecasts of future spot exchange rates. This result implies that there have been opportunities for speculative profit during the post Bretton Woods period. Observers of the floating rate system have also noted that exchange rates have been more volatile than they were anticipated to be in the 1960's. In this paper, the link between the volatility of exchange rates and the existence of opportunities for speculative profit is explored. The question answered in the paper is the following: if there were no opportunities for speculative profit, would exchange rates have been more stable? The answer is yes. This answer implies that speculation (intervention) based upon the forecasting equation described in the paper would be both profitable and stabilizing.

Effective Theory of Braid Excitations of Quantum Geometry in terms of Feynman Diagrams

We study interactions amongst topologically conserved excitations of quantum theories of gravity, in particular the braid excitations of four-valent spin networks. These have been shown previously to propagate and interact under evolution rules of spin foam models. We show that the dynamics of these braid excitations can be described by an effective theory based on Feynman diagrams. In this language, braids which are actively interacting are analogous to bosons, in that the topological conservation laws permit them to be singly created and destroyed. Exchanges of these excitations give rise to interactions between braids which are charged under the topological conservation rules.Comment: 23 pages, 7 figures. Accepted by Nucl. Phys.