More AdS_3 correlators

We compute three-point functions for the $SL(2,\mathbb R)$-WZNW model. After reviewing the case of the two-point correlator, we compute spectral flow preserving and nonpreserving correlation functions in the space-time picture involving three vertex operators carrying an arbitrary amount of spectral flow. When only one or two insertions have nontrivial spectral flow numbers, the method we employ allows us to find expressions without any constraint on the spin values. Unlike these cases, the same procedure restrains the possible spin configurations when three vertices belong to nonzero spectral flow sectors. We perform several consistency checks on our results. In particular, we verify that they are in complete agreement with previously computed correlators involving states carrying a single unit of spectral flow.Comment: 22 pages. Minor changes. Some references adde

Dirac electrons and domain walls: a realization in junctions of ferromagnets and topological insulators

We study a system of Dirac electrons with finite density of charge carriers coupled to an external electromagnetic field in two spatial dimensions, with a domain wall (DW) mass term. The interface between a thin-film ferromagnet and a three-dimensional topological insulator provides a condensed-matter realization of this model, when an out-of-plane domain wall magnetization is coupled to the TI surface states. We show how, for films with very weak intrinsic in-plane anisotropies, the torque generated by the edge electronic current flowing along the DW competes with an effective in-plane anisotropy energy, induced by quantum fluctuations of the chiral electrons bound to the wall, in a mission to drive the internal angle of the DW from a Bloch configuration towards a N\'eel configuration. Both the edge current and the induced anisotropy contribute to stabilize the internal angle, so that for weak intrinsic in-plane anisotropies DW motion is still possible without suffering from an extremely early Walker breakdown.Comment: 18 pages, 3 figure

Properties of ultra-cool dwarfs with Gaia. An assessment of the accuracy for the temperature determination

We aimed to assess the accuracy of the Gaia teff and logg estimates as derived with current models and observations. We assessed the validity of several inference techniques for deriving the physical parameters of ultra-cool dwarf stars. We used synthetic spectra derived from ultra-cool dwarf models to construct (train) the regression models. We derived the intrinsic uncertainties of the best inference models and assessed their validity by comparing the estimated parameters with the values derived in the bibliography for a sample of ultra-cool dwarf stars observed from the ground. We estimated the total number of ultra-cool dwarfs per spectral subtype, and obtained values that can be summarised (in orders of magnitude) as 400000 objects in the M5-L0 range, 600 objects between L0 and L5, 30 objects between L5 and T0, and 10 objects between T0 and T8. A bright ultra-cool dwarf (with teff=2500 K and \logg=3.5 will be detected by Gaia out to approximately 220 pc, while for teff=1500 K (spectral type L5) and the same surface gravity, this maximum distance reduces to 10-20 pc. The RMSE of the prediction deduced from ground-based spectra of ultra-cool dwarfs simulated at the Gaia spectral range and resolution, and for a Gaia magnitude G=20 is 213 K and 266 K for the models based on k-nearest neighbours and Gaussian process regression, respectively. These are total errors in the sense that they include the internal and external errors, with the latter caused by the inability of the synthetic spectral models (used for the construction of the regression models) to exactly reproduce the observed spectra, and by the large uncertainties in the current calibrations of spectral types and effective temperatures.Comment: 18 pages, 17 figures, accepted by Astronomy & Astrophysic

Macroeconomic Policies Interaction & the Symmetry of Financial Markets' Responses

This concise study analyses the symmetry of financial markets` responses to macroeconomic policy interaction in the United Kingdom. Employing the Vector Auto-regression (VAR) model on monthly data of the British financial sector and macroeconomic policies from January 1985 to August 2008, this study found that the equity and sovereign debt markets showed identical symmetry in response to macroeconomic policy interaction

Efetividade de uma intervenção digital na diminuição da prática de binge drinking entre frequentadores de baladas

OBJECTIVE: To evaluate the effectiveness of a web-based intervention in reducing binge drinking among nightclub patrons after six months. METHODS: We carried out a website survey with probabilistic sample in 31 nightclubs in the city of São Paulo, Brazil, which originated a randomized controlled trial with 1,057 participants. Those classified as problem drinkers (n = 465) using the Alcohol Use Disorders Identification Test were randomized into two study groups – intervention and control. The web-based intervention consisted of exposing the participants to a normative feedback screen about their alcohol consumption, characterizing the risks associated with amount consumed, money spent on drinks, drinking and driving, risk classification of Alcohol Use Disorders Identification Test, and tips to reduce damage. RESULTS: There was a significant reduction in the practice of binge drinking in the week estimated at 38% among participants in the intervention group after six months (p < 0.05). However, there was no significant reduction in the outcomes when we analyzed the intervention and control groups and at baseline and after sixth months, simultaneously. CONCLUSIONS: We cannot conclude that digital tools reduce the pattern of binge drinking among party goers in São Paulo. More studies are needed with this methodology because of its attractiveness to this type of group, given the privacy and speed that personalized information is transmitted.OBJETIVO: Avaliar, após seis meses, a efetividade de uma intervenção digital na diminuição da prática de binge drinking entre frequentadores de baladas. MÉTODOS: Foi realizado um inquérito de portal através de uma amostra probabilística em 31 baladas da cidade de São Paulo, a qual originou um ensaio controlado randomizado com 1.057 participantes. Aqueles classificados como uso problemático do álcool (n = 465) através do Alcohol Use Disorders Identification Test foram randomizados em dois grupos de estudo – intervenção e controle. A intervenção digital consistiu em expor os participantes a uma tela de feedback normativo sobre seu consumo de álcool, caracterizando os riscos associados à quantidade consumida, valores gastos com bebidas, beber e dirigir, classificação do risco do Alcohol Use Disorders Identification Test e dicas de redução de danos. RESULTADOS:Houve uma redução significativa da prática de binge drinking na semana estimada em 38% entre os participantes do grupo intervenção após seis meses (p < 0,05). Porém, não houve redução significativa nos desfechos quando se analisam os grupos intervenção e controle e os tempos início e seis meses após, simultaneamente. CONCLUSÕES: Não se pode concluir que as ferramentas digitais reduzem o padrão de binge drinking nos frequentadores de baladas paulistanas. São necessários mais estudos com esta metodologia devido ao caráter atrativo para esse grupo, tendo em vista a privacidade e a rapidez que as informações personalizadas são transmitidas

Strategic alliance in energy sector & implications for economic growth and technical efficiency: The case of petrobras and galp

This study stemmed from the lack of evidence and uncertainties regarding the economic and political effects of a strategic alliance between leading oil companies like Petrobras and Galp on their host economies. This paper investigates whether public and private corporations in the energy sector can influence the economic growth of their respective countries. A Panel data analysis was performed by employing quarterly data from (2006-2013). We also used Data Envelopment Analysis (DEA) approach to measure the technical efficiency (TE) effect of the alliance on the performance of both companies from 1999 to 2012. It was found the exploration and export of oil and gas do not play a significant role in output growth of the home economy and that exploration activities were inflationary, destabilising and inimical to growth, at least in the short-run. On another positive side, both companies showed increased technical efficiencies in the chosen time period. Petrobras enjoyed TE on average of 90% in the variables studied whereas Galp showed an average TE of 70%. These results reflect the corporate strategies of both firms, which focussed on achieving profitable and sustained growth and enhancing their efficiencies in their collective and individual activities

Collagen organization, polarization sensitivity and image quality in human corneas using second harmonic generation microscopy

In this paper, a Second-Harmonic-Generation (SHG) microscope was used to study the relationship between collagen structural arrangement, image quality and polarization sensitivity in human corneas with different organizations. The degree of order (or alternatively, the Structural Dispersion, SD) was quantified using the structure tensor method. SHG image quality was evaluated with different objective metrics. Dependence with polarization was quantified by means of a parameter defined as polarimetric modulation, which employs polarimetric SHG images acquired with four independent polarization states. There is a significant exponential relationship between the quality of the SHG images and the SD of the samples. Moreover, polarization sensitivity strongly depends on collagen arrangement. For quasi- or partially organized specimens, there is a polarization state that noticeably improves the image quality, providing additional information often not seen in other SHG images. This does not occur in non-organized samples. This fact is closely related to polarimetric modulation, which linearly decreases with the SD. Understanding in more detail the relationships that take place between collagen distribution, image quality and polarization sensitivity brings the potential to enable the development of optimized SHG image acquisition protocols and novel objective strategies for the analysis and detection of pathologies related to corneal collagen disorders, as well as surgery follow-ups

Particle statistics and lossy dynamics of ultracold atoms in optical lattices

Experimental control over ultracold quantum gases has made it possible to investigate low-dimensional systems of both bosonic and fermionic atoms. In closed one-dimensional systems there are many similarities in the dynamics of local quantities for spinless fermions and strongly interacting "hard-core" bosons, which on a lattice can be formalized via a Jordan-Wigner transformation. In this study, we analyze the similarities and differences for spinless fermions and hard-core bosons on a lattice in the presence of particle loss. The removal of a single fermion causes differences in local quantities compared with the bosonic case because of the different particle exchange symmetry in the two cases. We identify deterministic and probabilistic signatures of these dynamics in terms of local particle density, which could be measured in ongoing experiments with quantum gas microscopes

Culturo-Scientific Storytelling

In this article, we reflect on the functions of outreach in developing the modern scientific mind, and discuss its essential importance in the modern society of rapid technological development. We embed our approach to outreach in culturo-scientific thinking. This is constituted by embracing disciplinary thinking (in particular creativity) whilst appreciating the epistemology of science as an evolving dialogue of ideas, with numerous alternative perspectives and uncertain futures to be managed. Structuring scientific knowledge as an assemblage of interacting and evolving discipline-cultures, we conceive of a culturo-scientific storytelling to bring about positive transformations for the public in these thinking skills and ground our approach in quantum science and technologies (QST). This field has the potential to generate significant changes for the life of every citizen, and so a skills-oriented approach to its education, both formal and non-formal, is essential. Finally, we present examples of such storytelling in the case of QST, the classification and evaluation of which correspond to future work in which this narrative approach is studied in action