High-Resolution Simulations of Cosmic Microwave Background non-Gaussian Maps in Spherical Coordinates

We describe a new numerical algorithm to obtain high-resolution simulated maps of the Cosmic Microwave Background (CMB), for a broad class of non-Gaussian models. The kind of non-Gaussianity we account for is based on the simple idea that the primordial gravitational potential is obtained by a non-linear but local mapping from an underlying Gaussian random field, as resulting from a variety of inflationary models. Our technique, which is based on a direct realization of the potential in spherical coordinates and fully accounts for the radiation transfer function, allows to simulate non-Gaussian CMB maps down to the Planck resolution ($\ell_{\rm max} \sim 3,000$), with reasonable memory storage and computational time.Comment: 9 pages, 5 figures. Submitted to ApJ. A version with higher quality figures is available at http://www.pd.infn.it/~liguori/content.htm

Primordial non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure

The most direct probe of non-Gaussian initial conditions has come from bispectrum measurements of temperature fluctuations in the Cosmic Microwave Background and of the matter and galaxy distribution at large scales. Such bispectrum estimators are expected to continue to provide the best constraints on the non-Gaussian parameters in future observations. We review and compare the theoretical and observational problems, current results and future prospects for the detection of a non-vanishing primordial component in the bispectrum of the Cosmic Microwave Background and large-scale structure, and the relation to specific predictions from different inflationary models.Comment: 82 pages, 23 figures; Invited Review for the special issue "Testing the Gaussianity and Statistical Isotropy of the Universe" for Advances in Astronom

General CMB and Primordial Bispectrum Estimation I: Mode Expansion, Map-Making and Measures of f_NL

We present a detailed implementation of two bispectrum estimation methods which can be applied to general non-separable primordial and CMB bispectra. The method exploits bispectrum mode decompositions on the domain of allowed wavenumber or multipole values. Concrete mode examples constructed from symmetrised tetrahedral polynomials are given, demonstrating rapid convergence for known bispectra. We use these modes to generate simulated CMB maps of high resolution (l > 2000) given an arbitrary primordial power spectrum and bispectrum or an arbitrary late-time CMB angular power spectrum and bispectrum. By extracting coefficients for the same separable basis functions from an observational map, we are able to present an efficient and general f_NL estimator for a given theoretical model. The estimator has two versions comparing theoretical and observed coefficients at either primordial or late times, thus encompassing a wider range of models, including secondary anisotropies, lensing and cosmic strings. We provide examples and validation of both f_NL estimation methods by direct comparison with simulations in a WMAP-realistic context. In addition, we show how the full bispectrum can be extracted from observational maps using these mode expansions, irrespective of the theoretical model under study. We also propose a universal definition of the bispectrum parameter F_NL for more consistent comparison between theoretical models. We obtain WMAP5 estimates of f_NL for the equilateral model from both our primordial and late-time estimators which are consistent with each other, as well as with results already published in the literature. These general bispectrum estimation methods should prove useful for the analysis of nonGaussianity in the Planck satellite data, as well as in other contexts.Comment: 41 pages, 17 figure

Factorization in integrable systems with impurity

This article is based on recent works done in collaboration with M. Mintchev, E. Ragoucy and P. Sorba. It aims at presenting the latest developments in the subject of factorization for integrable field theories with a reflecting and transmitting impurity.Comment: 7 pages; contribution to the XIVth International Colloquium on Integrable systems, Prague, June 200

The effects of social spending on entrepreneurship in developed nations

Understanding how national policy can spur entrepreneurial activity is central to entrepreneurship research. Over the past decade, there has been a limited set of research findings to suggest that social spending may increase entrepreneurship in addition to serving more direct social purposes. We examine the topic through the lens of market failure theory and Austrian economics. In accordance with the Austrian perspective, we theorize that social spending increases the opportunity cost of entrepreneurship, thereby decreasing the attractiveness of entrepreneurship in comparison to salaried employment. Drawing from a sample of 31 developed countries spanning 2004–2011, we investigate the effects of social spending on entrepreneurial attitudes and activity. Our results indicate that country level social spending negatively affects entrepreneurial activity, business ownership, and the public’s view of entrepreneurship as a career choice. The findings suggest that social spending may be better suited for addressing social issues compared to spurring entrepreneurial attitudes or activity. Our findings have implications for both the entrepreneurship and national policy literature

Entrepreneurial value creation: conceptualizing an exchange-based view of entrepreneurship

4sìopenPurpose: This paper proposes an Exchange-Based View of the value creation process. The Borrowing from marketing literature, the EBV advances that entrepreneurs and stakeholders are tied by exchange relationships, through which they co-create value by reciprocally making and realizing promises of value. Design/methodology/approach: Propositions are developed and offered to advance the role of exchange in the entrepreneurial value creation process. Findings: The authors conceptualize the enterprise as a system of exchange relationships between entrepreneurs and their stakeholders, thus proposing an exchange-based view of entrepreneurship. Originality/value: Such an account of the role of entrepreneurs and of their relationship with the stakeholders has meaningful implications for our understanding of the entrepreneurial tasks of opportunity recognition and exploitation.openPinelli M.; Lechner C.; Kraus S.; Liguori E.Pinelli, M.; Lechner, C.; Kraus, S.; Liguori, E

Stochastic Inflation and the Lower Multipoles in the CMB Anisotropies

We generalize the treatment of inflationary perturbations to deal with the non-Markovian colored noise emerging from any realistic approach to stochastic inflation. We provide a calculation of the power-spectrum of the gauge-invariant comoving curvature perturbation to first order in the slow-roll parameters. Properly accounting for the constraint that our local patch of the Universe is homogeneous on scales just above the present Hubble radius, we find a blue tilt of the power-spectrum on the largest observable scales, in agreement with the WMAP data which show an unexpected suppression of the low multipoles of the CMB anisotropy. Our explanation of the anomalous behaviour of the lower multipoles of the CMB anisotropies does not invoke any ad-hoc introduction of new physical ingredients in the theory.Comment: 9 pages, 2 figure