The closet non-Gaussianity of anisotropic Gaussian fluctuations

In this paper we explore the connection between anisotropic Gaussian fluctuations and isotropic non-Gaussian fluctuations. We first set up a large angle framework for characterizing non-Gaussian fluctuations: large angle non-Gaussian spectra. We then consider anisotropic Gaussian fluctuations in two different situations. Firstly we look at anisotropic space-times and propose a prescription for superimposed Gaussian fluctuations; we argue against accidental symmetry in the fluctuations and that therefore the fluctuations should be anisotropic. We show how these fluctuations display previously known non-Gaussian effects both in the angular power spectrum and in non-Gaussian spectra. Secondly we consider the anisotropic Grischuk-Zel'dovich effect. We construct a flat space time with anisotropic, non-trivial topology and show how Gaussian fluctuations in such a space-time look non-Gaussian. In particular we show how non-Gaussian spectra may probe superhorizon anisotropy

Evidence for non-Gaussianity in the COBE DMR Four Year Sky Maps

We introduce and study the distribution of an estimator for the normalized bispectrum of the Cosmic Microwave Background (CMB) anisotropy. We use it to construct a goodness of fit statistic to test the coadded 53 and 90 GHz COBE-DMR 4 year maps for non-Gaussianity. Our results indicate that Gaussianity is ruled out at the confidence level in excess of 98%. This value is a lower bound, given all the investigated systematics. The dominant non-Gaussian contribution is found near the multipole of order $\ell=16$. Our attempts to explain this effect as caused by the diffuse foreground emission from the Galaxy have failed. We conclude that unless there exists a microwave foreground emission which spatially correlates neither with the DIRBE nor Haslam maps, the cosmological CMB anisotropy is genuinely non-Gaussian.Comment: 16 pages, 3 figs uses aasms4.tex, revised and accepted to Ap. J. Let

Where is the COBE maps' non-Gaussianity?

We review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. We present some new results concerning the effect of the galactic cut upon the non-Gaussian signal. These findings imply a localization of the non-Gaussian signal on the Northern galactic hemisphere.Comment: Proceedings of COSMO98 Asiloma

Non-Gaussian Spectra

Gaussian cosmic microwave background skies are fully specified by the power spectrum. The conventional method of characterizing non-Gaussian skies is to evaluate higher order moments, the n-point functions and their Fourier transforms. We argue that this method is inefficient, due to the redundancy of information existing in the complete set of moments. In this paper we propose a set of new statistics or non-Gaussian spectra to be extracted out of the angular distribution of the Fourier transform of the temperature anisotropies in the small field limit. These statistics complement the power spectrum and act as localization, shape, and connectedness statistics. They quantify generic non-Gaussian structure, and may be used in more general image processing tasks. We concentrate on a subset of these statistics and argue that while they carry no information in Gaussian theories they may be the best arena for making predictions in some non-Gaussian theories. As examples of applications we consider superposed Gaussian and non-Gaussian signals, such as point sources in Gaussian theories or the realistic Kaiser-Stebbins effect. We show that in these theories non-Gaussianity is only present in a ring in Fourier space, which is best isolated in our formalism. Subtle but strongly non-Gaussian theories are also written down for which only non-Gaussian spectra may accuse non-Gaussianity.Comment: 23 pages (20 figures), uses RevTex and epsfig, submitted to PRD. Figures available from ftp://euclid.tp.ph.ic.ac.uk/pub/magueijo/ng/ (in 4 files). Also, in same site, ng8.uu with it all (preferable

On the Nature of Income Inequality Across Nations

In this paper, we investigate the nature of income inequality across nations by first estimating, testing, and distinguishing between two types of aggregate production functions: the extended neoclassical model and a mincerian formulation of schooling-returns to skills. Next, given our panel-data estimates, we proceed in decomposing the variance of the (log) level of output per-worker in 1985 into that of three distinct factors: productivity, human capital, and the dynamic incentives to accumulate capital. Finally, we classify a group of 95 countries according to their relative position (above or below average) for each of these factors. The picture that emerges from these last two exercises is one where countries grew in the past for different reasons, which should be considered for policy design. Although there is not a single-factor explanation for the difference in output per-worker across nations, it seems that productivity differences can explain a considerable portion of income inequality, followed second by dynamic inefficiencies and third by human capital accumulation.

La cadena de valor de los productos forestales y los costes de su remodelación: impacto multirregional de la reducción de las industrias de pulpa y papel en Portugal

Las evaluaciones macroeconómicas de la industria forestal tienden a subestimar su impacto en las economías regionales. Este trabajo propone un concepto más amplio – la "cadena de valor de los productos forestales"- que incluye la contribución de las actividades que dependen (directa e indirectamente) de la silvicultura y los productos forestales. Con una metodología basada en un modelo de input-output multirregional y centrado en la economía portuguesa. Los resultados elucidan el papel del eucalipto en las producciones de pulpa, papel y cartón y artículos de papel y cartón. Finalmente, se evalúan las consecuencias macroeconómicas proyectadas para una reducción de estas producciones.Forestry industry macroeconomic assessments typically concentrate on the production, harvesting, and earliest processing of wood products, underestimating the full range of forests impacts in regional economies. This work proposes a broader concept – “forestry products value chain”– that ponders the contribution of the downstream activities relying (directly and indirectly) on Silviculture and Forestry products. The paper adopts a methodology based on a Multi-Regional Input-Output framework. We apply this approach to the Portuguese economy. Results clarify the role of eucalyptus in “Pulp”, “Paper and Cardboard” and “Paper and Cardboard Articles”. Finally, the projected wider macroeconomic consequences from a reduction of these productions is evaluated

Causality, randomness, and the microwave background

Fluctuations in the cosmic microwave background (CMB) temperature are being studied with ever increasing precision. Two competing types of theories might describe the origins of these fluctuations: ``inflation'' and ``defects''. Here we show how the differences between these two scenarios can give rise to striking signatures in the microwave fluctuations on small scales, assuming a standard recombination history. These should enable high resolution measurements of CMB anisotropies to distinguish between these two broad classes of theories, independent of the precise details of each.Comment: uuencoded tex file and 4 postscript figure files, 8 pages. Also available at http://euclid.tp.ph/Papers/index.html; Changes: Minor changes reflect final published versio

Avaliação do desempenho financeiro das empresas do setor eléctrico em Portugal

A avaliação do desempenho financeiro do sector elétrico tem sido o foco de atenção de diversos estudos, mas existe uma escassez de literatura científica que aborde especificamente o desempenho financeiro das empresas deste sector. Assim, o presente trabalho tem como objetivo avaliar o desempenho financeiro das empresas reguladas que operam no mercado elétrico Português. Com este objetivo em mente, propõe-se uma estrutura de modelagem que combina o uso do método de estimação Generalized Method of Moments (GMM) com a análise Data Envelopment Analysis (DEA). Este estudo centra-se no período entre 2010 e 2014, altura em que o governo português necessitou de ajuda financeira externa. O método de estimação GMM permitiu selecionar as variáveis corporativas intrínsecas, que foram então usadas para avaliar o desempenho financeiro das empresas do setor elétrico através do modelo DEA Slack Based Measure (SBM). Neste contexto, o retorno sobre o património líquido (ROE), a alavancagem (Leverage) e os fluxos de caixa sobre o total do ativo (CFTA) foram selecionados como outputs, enquanto o valor da soma das depreciações e das amortizações sobre o total de ativos (DATA) foram considerados como inputs. Os resultados sugerem que enquanto em 2010 a maioria das empresas não eficientes deveriam investir em novos ativos fixos de modo a tornarem-se eficientes, em 2014, uma percentagem expressiva de empresas não eficientes deve diminuir este tipo de investimento. Adicionalmente, em ambos os períodos, a maioria das empresas do sector elétrico não eficientes deveria aumentar o seu ROE para se tornar eficiente, destacando o papel do ROE na explicação da eficiência financeira. Em 2014, as empresas não eficientes são capazes de gerar fluxos de caixa com eficiência, uma vez que quase não são necessários ajustes em relação aos valores de CFTA obtidos por estas empresas. Por fim, a necessidade de promover a alavancagem para aumentar o desempenho financeiro é mais evidente em 2010 do que em 2014, reconhecendo que os novos investimentos feitos neste período utilizam capital alheio