Noncommutative Quantum Field Theories

We start by reviewing the formulation of noncommutative quantum mechanics as a constrained system. Then, we address to the problem of field theories defined on a noncommutative space-time manifold. The Moyal product is introduced and the appearance of the UV/IR mechanism is exemplified. The emphasis is on finding and analyzing noncommutative quantum field theories which are renormalizable and free of nonintegrable infrared singularities. In this last connection we give a detailed discussion of the quantization of the noncommutative Wess-Zumino model as well as of its low energy behavior.Comment: 45 pages, 11 figures, lectures delivered at the XII Jorge Andre Swieca Summar School, Section Particles and Fields, Campos de Jordao, Brazil, 2003. Three references added, typos correcte

Duality Symmetry in the Schwarz-Sen Model

The duality symmetric but not manifestly covariant action proposed by Schwarz-Sen is canonically quantized in the Coulomb gauge. The resulting theory turns out to be, nevertheless, relativistically invariant. It is shown, afterwards, that the Schwarz-Sen model naturally emerges when duality is implemented as a local symmetry of sourceless electrodynamics. This implies in the equivalence of these theories at the quantum level.Comment: 11 pages, latex, to be published in "Trends in Theoretical Physics II", edited by H. Falomir, R. E. Gamboa Saravi and F. Schaposnik, AIP Conference Proceedings 484, 199

On the quantum dynamics of non-commutative systems

This is a review paper concerned with the global consistency of the quantum dynamics of non-commutative systems. Our point of departure is the theory of constrained systems, since it provides a unified description of the classical and quantum dynamics for the models under investigation. We then elaborate on recently reported results concerned with the sufficient conditions for the existence of the Born series and unitarity and turn, afterwards, into analyzing the functional quantization of non-commutative systems. The compatibility between the operator and the functional approaches is established in full generality. The intricacies arising in connection with the explicit computation of path integrals, for the systems under scrutiny, is illustrated by presenting the detailed calculation of the Feynman kernel for the non-commutative two dimensional harmonic oscillator.Comment: 19 pages, title changed, version to be published in Brazilian Journal of Physic

Comment on "Attractive Forces between Electrons in 2 + 1 Dimensional QED"

It is shown that a model recently proposed for numerical calculations of bound states in QED$_3$ is in fact an improper truncation of the Aharonov-Bohm potential.Comment: 4 page

Factors Contributing to Participation in Web-based Surveys among Italian University Graduates

An established yearly survey aimed at monitoring the employment opportunities of Italian graduates, traditionally carried out with Cati methods, has been integrated during the last few years with Cawi. Cawi has become increasingly crucial due to the high number of graduates involved in the survey, which has mandated a reduction in fieldwork duration and unit costs. Although the seven Cawi surveys used here have different substantive and methodological characteristics, preliminary analysis reveals a common trend: the utmost participation is observed during the first few days immediately following initiation of fieldwork and, to a lesser degree, the delivery of follow-up reminders. Web respondents comprise a self-selected subgroup of the target population, having better academic performance and greater computer skills. A Cox regression model estimating response probability (or response time) shows, besides the obvious effects of certain personal and survey design characteristics, that faster response times are expressed by graduates in science or engineering and reporting good computer skills, whereas the fields of medicine/health and defence/security and no computer skills give rise to lower response probability. Ways to use these findings for fine-tuning data collection are discussed.Cawi surveys, Response rate, University graduates,Cox regression

Nonperturbative solution of the Nonconfining Schwinger Model with a generalized regularization

Nonconfining Schwinger Model [AR] is studied with a one parameter class of kinetic energy like regularization. It may be thought of as a generalization over the regularization considered in [AR]. Phasespace structure has been determined in this new situation. The mass of the gauge boson acquires a generalized expression with the bare coupling constant and the parameters involved in the regularization. Deconfinement scenario has become transparent at the quark-antiquark potential level.Comment: 13 pages latex fil

Multi-Agents Systems and Territory: Concepts, Methods and Applications

This paper analyses the multi-agents systems that are now considered the best tool to simulate and study real world. We review the main characteristics of a multi-agents system, namely interactions and cooperations of agents, communications and behaviours between them and finally the schedule of actions and jobs assignment to agents. The multi-agents system approach is increasingly applied in social and economic sciences; so we study mainly the territorial applications. In these applications new characteristics arise from the consideration of territory (land and space where the agents live or territory as an agent in itself, that evolves in the time). We study possible new applications of multi-agents applied to the territory (for instance, to define town planning policies or to locate dangerous facilities). Furthermore we study new tools to make operational multi-agents systems (mainly Swarm, the toolkit of Santa Fe Institute). With Swarm we present two kind of territorial applications: with located agents (fixed in space) and with not located agents (moving in the space). Finally we show the results of these applications.