Generating Black Strings in Higher Dimensions

Starting with a Zipoy-Voorhees line element we construct and study the three parameter family of solutions describing a deformed black string with arbitrary tension.Comment: 11 pages, 2 figures, accepted for publication in J. Mod. Phys. Lett.

Penrose Limits, the Colliding Plane Wave Problem and the Classical String Backgrounds

We show how the Szekeres form of the line element is naturally adapted to study Penrose limits in classical string backgrounds. Relating the "old" colliding wave problem to the Penrose limiting procedure as employed in string theory we discuss how two orthogonal Penrose limits uniquely determine the underlying target space when certain symmetry is imposed. We construct a conformally deformed background with two distinct, yet exactly solvable in terms of the string theory on R-R backgrounds, Penrose limits. Exploiting further the similarities between the two problems we find that the Penrose limit of the gauged WZW Nappi-Witten universe is itself a gauged WZW plane wave solution of Sfetsos and Tseytlin. Finally, we discuss some issues related to singularity, show the existence of a large class of non-Hausdorff solutions with Killing Cauchy Horizons and indicate a possible resolution of the problem of the definition of quantum vacuum in string theory on these time-dependent backgrounds.Comment: Some misprints corrected. Matches the version in print. To appear in Classical & Quantum Gravit

Visual Perceptual Difficulties and Under-Achievement at School in a Large Community-Based Sample of Children

Difficulties with visual perception (VP) are often described in children with neurological or developmental problems. However, there are few data regarding the range of visual perceptual abilities in populations of normal children, or on the impact of these abilities on children's day-to-day functioning. Methods Data were obtained for 4512 participants in an ongoing birth cohort study (Avon Longitudinal Study of Parents and Children; ALSPAC). The children's mothers responded to questions designed to elicit indications of visual perceptual difficulties or immaturity, when their children were aged 13 years. We examined associations with standardised school test results in reading and in mathematics at age 1314 years (SATS-KS3), accounting for potential confounders including IQ. Results Three underlying factors explained half the variance in the VP question responses. These correlated best with questions on interpreting cluttered scenes; guidance of movement and face recognition. The adjusted parameter estimates (95% CI) for the cluttered-scenes factor (0.05; 0.02 to 0.08; p<0.001) suggested positive associations with the reading test results whilst that for the guidance-of-movement factor (0.03; 0.00 to 0.06; p = 0.026) suggested positive association with the mathematics results. The raw scores were associated with both test results. Discussion VP abilities were widely distributed in this sample of 13-year old children. Lower levels of VP function were associated with under-achievement in reading and in mathematics. Simple interventions can help children with VP difficulties, so research is needed into practicable, cost-effective strategies for identification and assessment, so that support can be targeted appropriately

On the Entropy and the Density Matrix of Cosmological Perturbations

We look at the transition to the semiclassical behaviour and the decoherence process for the inhomogeneous perturbations in the inflationary universe. Two different decoherence mechanisms appear: one dynamical, accompanied with a negligible, if at all, entropy gain, and the other, effectively irreversible dephasing, due to a rapid variation in time of the off-diagonal density matrix elements in the post-inflationary epoch. We thus settle the discrepancies in the entropy content of perturbations evaluated by different authors.Comment: LaTeX2e with the epsf packag

Return to Play Following Shoulder Stabilization: A Systematic Review and Meta-analysis.

BackgroundAnterior shoulder instability can be a disabling condition for the young athlete; however, the best surgical treatment remains controversial. Traditionally, anterior shoulder instability was treated with open stabilization. More recently, arthroscopic repair of the Bankart injury with suture anchor fixation has become an accepted technique.HypothesisNo systematic reviews have compared the rate of return to play following arthroscopic Bankart repair with suture anchor fixation with the Bristow-Latarjet procedure and open stabilization. We hypothesized that the rate of return to play will be similar regardless of surgical technique.Study designSystematic review; Level of evidence, 4.MethodsWe performed a systematic review and meta-analysis focused on return to play following shoulder stabilization. Inclusion criteria included studies in English that reported on rate of return to play and clinical outcomes following primary arthroscopic Bankart repair with suture anchors, the Latarjet procedure, or open stabilization. Statistical analyses included Student t tests and analyses of variance.ResultsSixteen papers reporting on 1036 patients were included. A total of 545 patients underwent arthroscopic Bankart repair with suture anchors, 353 with the Latarjet procedure, and 138 with open repair. No significant difference was found in patient demographic data among the studies. Patients returned to sport at the same level of play (preinjury level) more consistently following arthroscopic Bankart repair (71%) or the Latarjet procedure (73%) than open stabilization (66%) (P < .05). Return to play at any level and postoperative Rowe scores were not significantly different among studies. Recurrent dislocation was significantly less following the Latarjet procedure (3.5%) than after arthroscopic Bankart repair (6.6%) or open stabilization (6.7%) (P < .05).ConclusionThis systematic review demonstrates a greater rate of return to play at the preinjury level following arthroscopic Bankart repair and the Latarjet procedure than open stabilization. Despite this difference, >65% of all treated athletes returned to sport at their preinjury levels, with other outcome measures being similar among the treatment groups. Therefore, arthroscopic Bankart repair, the Latarjet procedure, and open stabilization remain good surgical options in the treatment of the athlete with anterior shoulder instability

Long-Term Optical Monitoring of Eta Carinae. Multiband light curves for a complete orbital period

The periodicity of 5.5 years for some observational events occurring in Eta Carinae manifests itself across a large wavelength range and has been associated with its binary nature. These events are supposed to occur when the binary components are close to periastron. To detect the previous periastron passage of Eta Car in 2003, we started an intensive, ground-based, optical, photometric observing campaign. We continued observing the object to monitor its photometric behavior and variability across the entire orbital cycle. Our observation program consisted of daily differential photometry from CCD images, which were acquired using a 0.8 m telescope and a standard BVRI filter set at La Plata Observatory. The photometry includes the central object and the surrounding Homunculus nebula. We present up-to-date results of our observing program, including homogeneous photometric data collected between 2003 and 2008. Our observations demonstrated that Eta Car has continued increasing in brightness at a constant rate since 1998. In 2006, it reached its brightest magnitude (V ~ 4.7) since about 1860s. The object then suddenly reverted its brightening trend, fading to V = 5.0 at the beginning of 2007, and has maintained a quite steady state since then. We continue the photometric monitoring of Eta Car in anticipation of the next "periastron passage", predicted to occur at the beginning of 2009.Comment: Accepted by A&A. The paper contains 3 figures and 2 table

Environmental Evaluation and Global Development Institutions

Evaluation is increasingly important for finding sustainable solutions for the people and the planet, based on a systematic analysis of what works, for whom, and under what circumstances, and to contribute to the achievement of the Sustainable Development Goals, as they pertain to the environment. This book explores why the Global Environment Facility (GEF) invests in evaluation for accountability and learning to inform its decision-making on programming priorities, and how this leads to wiser funding decisions and better program performance on the ground. The book is based on real-life experiences of how to make evaluation count for international environmental action. Drawing upon comprehensive evaluations of the GEF, it provides unique insights from authors responsible for designing, implementing, and disseminating the findings of the evaluations. No other multilateral development or environment agency places evaluation fully at the center of their decision-making. The book outlines the trends in the global environment and the changing landscape of international environmental finance. It defines the role of the GEF and explains its institutional framework and the unique partnership that involves donor and recipient countries, multilateral development banks, UN agencies, nongovernmental organizations (NGOs), and national agencies in the developing countries. Further, it provides useful pointers to other organizations wishing to enhance evidence-based decision-making for improving their relevance, performance, and impact. The book will be most suitable for graduate-level, specialized study in a variety of disciplines such as environmental and development economics, political science, international relations, geography, sociology, and social anthropology

Non-Abelian T-duality in Pre-Big-Bang Cosmology

We study the impact of non-Abelian T-duality transformations on a string based cosmological model. The implementation of the pre-big-bang scenario is investigated. We found a region of the dual phase where such a picture is possible.Comment: 15 pages, LaTeX, 3 figure

Locally suppressed transverse-field protocol for diabatic quantum annealing

Diabatic quantum annealing (DQA) is an alternative algorithm to adiabatic quantum annealing that can be used to circumvent the exponential slowdown caused by small minima in the annealing energy spectrum. We present the locally suppressed transverse-field (LSTF) protocol, a heuristic method for making stoquastic optimization problems compatible with DQA. We show that, provided an optimization problem intrinsically has magnetic frustration due to inhomogeneous local fields, a target qubit in the problem can always be manipulated to create a double minimum in the energy gap between the ground and first excited states during the evolution of the algorithm. Such a double energy minimum can be exploited to induce diabatic transitions to the first excited state and back to the ground state. In addition to its relevance to classical and quantum algorithmic speedups, the LSTF protocol enables DQA proof-of-principle and physics experiments to be performed on existing hardware, provided independent controls exist for the transverse qubit magnetization fields. We discuss the implications on the coherence requirements of the quantum annealing hardware when using the LSTF protocol, considering specifically the cases of relaxation and dephasing. We show that the relaxation rate of a large system can be made to depend only on the target qubit, presenting opportunities for the characterization of the decohering environment in a quantum annealing processor