On the Short Distance Behavior of the Critical Ising Model Perturbed by a Magnetic Field

We apply here a recently developed approach to compute the short distance corrections to scaling for the correlators of all primary operators of the critical two dimensional Ising model in a magnetic field. The essence of the method is the fact that if one deals with O.P.E. Wilson coefficients instead of correlators, all order I.R. safe formulas can be obtained for the perturbative expansion with respect to magnetic field. This approach yields in a natural way the expected fractional powers of the magnetic field, that are clearly absent in the naive perturbative expression for correlators. The technique of the Mellin transform have been used to compute the I.R. behavior of the regularized integrals. As a corollary of our results, by comparing the existing numerical data for the lattice model we give an estimate of the Vacuum Expectation Value of the energy operator, left unfixed by usual nonperturbative approaches (Thermodynamic Bethe Ansatz).Comment: 19 pages, LATEX, 2 figure

On the c-theorem in more than two dimensions

Several pieces of evidence have been recently brought up in favour of the c-theorem in four and higher dimensions, but a solid proof is still lacking. We present two basic results which could be useful for this search: i) the values of the putative c-number for free field theories in any even dimension, which illustrate some properties of this number; ii) the general form of three-point function of the stress tensor in four dimensions, which shows some physical consequences of the c-number and of the other trace-anomaly numbers.Comment: Latex, 7 pages, 1 tabl

“The role of diagnostics in the restoration project”

Over the last few years, in the field of restoration and conservation, the techniques used to evaluate the extent of damage are becoming increasingly more important before carrying out any work on a historical building. The diagnostic phase is the instrumental, methodological and procedural means of guidance and control during the preliminary cognitive examinations of the building which requires work. For this reason, in the restoration project, the procedural sequence is heavily based to the cognitive phase. In order to evaluate the conservational state of a structure correctly, it is necessary to understand the symptoms of the degradation and the principal cause. When this correlation is unclear there follows the planning and carrying out of a series of cognitive investigations. There is a preference in using indirectly destructive or non destructive investigative techniques to evaluate the state of the damage and degradation of monuments. These tests, which are carried out in situ, are based on identifying global physical properties present in the walls or the walls’ components and provide information about their behaviour. This study presents the planning and implementation of a series of surveys, carried out in situ, preliminary to structural consolidation and redevelopment work on a medieval castle: the castle of Cancellara (South Italy)

Fermions, Anomaly and Unitarity in High-Energy Electroweak Scattering

We report the "state of the art" of the problem of $B+L$ violation in high-energy electroweak scatterings. Results of various analyses point toward (though do not prove rigorously yet) the "half-suppression", i.e., that the $B+L$ violating cross section remains suppressed at least by the negative exponent of the single instanton action, at all energies. Most interesting techniques developed in this field are reviewed. Particular attention is paid to unitarity constraints on the anomalous cross section, and to some conceptual problem involving the use of the optical theorem in the presence of instantons.Comment: 59 (Latex) pages (+13 postscript figures (1075 blocks) available by e-mail request), GEF-Th-17/199

Short distance behaviour of correlators in the 2D Ising model in a magnetic field

We study the spin-spin, spin-energy and energy-energy correlators in the 2d Ising model perturbed by a magnetic field. We compare the results of a set of high precision Montecarlo simulations with the predictions of two different approximations: the Form Factor approach, based on the exact S-matrix description of the model, and a short distance perturbative expansion around the conformal point. Both methods give very good results, the first one performs better for distances larger than the correlation length, while the second one is more precise for distances smaller than the correlation length. In order to improve this agreement we extend the perturbative analysis to the second order in the derivatives of the OPE constants.Comment: 46 pages, 10 figures, final version to appear in Nucl. Phys.

Structure, regulation, and function of protein tyrosine phosphatases

The phosphorylation of tyrosyl residues in proteins is an essential aspect of many signal transduction events, including the control of both normal and neoplastic cell growth and proliferation. Since the earliest observations of tyrosine phosphorylation, it has been appreciated that this is a reversible process in which the net level of phosphate in a target substrate reflects the balance between the competing action of kinases and phosphatases. Thus, in cells transformed by temperature-sensitive mutants of Rous sarcoma virus, an elevation in the levels of phosphotyrosine is observed at the permissive temperature, at which the kinase is active; however, if the cells are shifted to the nonpermissive temperature, at which the kinase is inactivated, a rapid dephosphorylation of tyrosyl residues ensues due to the action of protein tyrosine phosphatases (PTPases) (Sefton et al. 1980). The last 10 years has witnessed great progress in the characterization of the protein tyrosine kinases, whereas..

Theory of mind in the social sciences: an experiment on strategic thinking in children

This study investigates mentalizing and strategic thinking in children in elementary school age (from 7 to 12 years old). Drawing from previous literature in behavioral and experiments economics and cognitive science, we conduct experiments in which children of different ages make choices in a series of one-shot, simultaneous move two-person games in normal form. We test the ability of our subjects to reason strategically and compare their behavioral patterns with those of adult players engaged in similar tasks (Di Guida and Devetag 2012). Our results show that even younger children are capable of perspective taking: they seem to grasp the essence of strategic thinking, to recognize similarities across games, and behave consistently. In addition, children are sensitive to the attractive power of focal points (Di Guida and Devetag 2012), which are perceived as natural coordination devices even when they are not part of the game equilibria, in line with previous results. Children are also able to perceive the risk-return tradeoffs implied in strategic decisions, as shown by their preference for \u201csafe\u201d strategies (i.e., strategies yielding an acceptable payoff for any choice of the opponent). Finally, only a minority behaves according to na\uefve heuristics such as opting for the strategy giving the maximum payoff. Our findings contribute to the interdisciplinary literature on the origin of fairness-based norms within societies and on the cognitive and social determinants of strategic interaction

Theory of mind in the social sciences: an experiment on strategic thinking in children

This study investigates mentalizing and strategic thinking in children in elementary school age (from 7 to 12 years old). Drawing from previous literature in behavioral and experiments economics and cognitive science, we conduct experiments in which children of different ages make choices in a series of one-shot, simultaneous move two-person games in normal form. We test the ability of our subjects to reason strategically and compare their behavioral patterns with those of adult players engaged in similar tasks (Di Guida and Devetag 2012). Our results show that even younger children are capable of perspective taking: they seem to grasp the essence of strategic thinking, to recognize similarities across games, and behave consistently. In addition, children are sensitive to the attractive power of focal points (Di Guida and Devetag 2012), which are perceived as natural coordination devices even when they are not part of the game equilibria, in line with previous results. Children are also able to perceive the risk-return tradeoffs implied in strategic decisions, as shown by their preference for “safe” strategies (i.e., strategies yielding an acceptable payoff for any choice of the opponent). Finally, only a minority behaves according to naïve heuristics such as opting for the strategy giving the maximum payoff. Our findings contribute to the interdisciplinary literature on the origin of fairness-based norms within societies and on the cognitive and social determinants of strategic interaction

Non Perturbative Renormalization Group, momentum dependence of nn-point functions and the transition temperature of the weakly interacting Bose gas

We propose a new approximation scheme to solve the Non Perturbative Renormalization Group equations and obtain the full momentum dependence of $n$-point functions. This scheme involves an iteration procedure built on an extension of the Local Potential Approximation commonly used within the Non Perturbative Renormalization Group. Perturbative and scaling regimes are accurately reproduced. The method is applied to the calculation of the shift $\Delta T_c$ in the transition temperature of the weakly repulsive Bose gas, a quantity which is very sensitive to all momenta intermediate between these two regions. The leading order result is in agreement with lattice calculations, albeit with a theoretical uncertainty of about 25%. The next-to-leading order differs by about 10% from the best accepted result

High precision Monte Carlo study of the 3D XY-universality class

We present a Monte Carlo study of the two-component $\phi^4$ model on the simple cubic lattice in three dimensions. By suitable tuning of the coupling constant $\lambda$ we eliminate leading order corrections to scaling. High statistics simulations using finite size scaling techniques yield $\nu=0.6723(3)[8]$ and $\eta=0.0381(2)[2]$, where the statistical and systematical errors are given in the first and second bracket, respectively. These results are more precise than any previous theoretical estimate of the critical exponents for the 3D XY universality class.Comment: 13 page