Two-dimensional Quantum Field Models (with applications to Statistical Mechanics)

Two dimensional toy models display, in a gentler setting, manysalient aspects of Quantum Field Theory. Here I discuss a concrete two dimensional case, the Thirring model, which illustrates several important concepts of this theory: the anomalous dimension of the fields; the exact solvability; the anomalies of the Ward-Takahashi identities. Besides, I give a glimpse of the decisive role that this model plays in the study of an apparently unrelated topic: correlation critical exponents of two dimensional lattice systems of Statistical Mechanics.Comment: 10 pages; International Conference on Mathematical Physics 2012 - Topical Section: Quantum Field Theor

A ten-step model for solving ethical dilemmas

This paper suggests a ten-step model for solving ethical dilemmas taking into account a wide spectrum of ethical values. The model has a prescriptive content that should help decision-makers to find a solution to ethical dilemmas according to the dictates suggested by moral obligation. For each step of the model, different types of simplification procedures are used in order to guide the decision-maker progressively toward a satisfactory solution. We begin with a discussion of the main characteristics that the model should possess. The paper then gives a detailed description of the single steps of the model. Lastly, a case study was analysed

The Mass Function of Cosmic Structures with Non-Spherical Collapse

Non-spherical dynamical approximations and models for the gravitational collapse are used to extend the well-known Press \& Schechter (PS) approach, in order to determine analytical expressions for the mass function of cosmic structures. The problem is rigorously set up by considering the intrinsic Lagrangian nature of the mass function. The Lagrangian equations of motion of a cold and irrotational fluid in single-stream regime show that the shear, which is non-locally determined by all the matter field, is the quantity which characterizes non-spherical perturbations. The Zel'dovich approximation, being a self-consistent first-order Lagrangian and local one, is used as a suitable guide to develop realistic estimates of the collapse time of a mass clump, starting from the local initial values of density and shear. Both Zel'dovich-based \an\ and models and the homogeneous ellipsoidal model predict that more large-mass objects are expected to form than the usual PS relation. In particular, the homogeneous ellipsoid model is consistent at large masses with a Press \& Schechter mass function with a lower value of the \dc\ parameter, in the range 1.4$\div$1.6. This gives a dynamical explanation of why lower \dc\ values have been found to fit the results of several N-body simulations. When more small-scale structure is present, highly non-linear dynamical effects can effectively slow down the collapse rate of a perturbation, increasing the effective value of \dc. This may have interesting consequences on the abundance of large-mass high-redshift objects.Comment: 16 pages+5 figures, uuencoded postscript file, submitted to Ap

What R&D assets say about firm profitability

Research and development (R&D) activities are usually considered a key factor for achieving superior performances. Using a sample of 11,897 manufacturing Italian firms, we examine the relationship between R&D expenditure that is capitalized as an intangible asset and some proxies of firm profitability over a period of four years in order to explore whether R&D assets can help investors in the identification of profitable firms. Contrary to expectations, this paper found a negative and/or an insignificant association between R&D assets and proxies of firm profitability. Although there are several possible explanations for this result, what we learn from this study is that R&D assets are not on average a reliable indicator for detecting profitable firms. Research findings revealed that firms with R&D assets appear to be not so profitable, large and levered