Quantum model of Fraunhofer diffraction for polarized pure states and connection with the Huygens-Fresnel principle

A quantum model of Fraunhofer diffraction by an aperture is presented. The diaphragm is considered as a device for measuring the three spatial coordinates of the particles passing through the aperture. This position measurement is described by a matrix similar to the S-matrix of the scattering theory. Due to the measurement of the longitudinal coordinate, the wavelets emission involved in the Huygens-Fresnel principle can occur from several neighboring wavefronts instead of just one. These wavefronts contribute with different weights forming a distribution whose width ${\Delta}z$ can be fitted to data from measurement of the diffracted wave intensity. The latter undergoes a damping which increases with ${\Delta}z$ and with the diffraction angle. Whatever ${\Delta}z$, the values at large angles are plausible contrary to those of the scalar theories of wave optics. The position measurement modifies the polarization states. For an incident photon in an elliptically polarized pure state, diffraction can rotate the ellipse axes by an angle which is a function of the diffraction angle and which can be fitted to the data from measurement of the polarization of the photon detected beyond the diaphragm.Comment: 14 pages, 4 figure

THE DESIGN OF A PLURAL LAND USE PLANNIG SYSTEM - A TENTATIVE PROPOSAL FROM AN ITALIAN PERSPECTIVE

The main approaches to planning developed during planning history are essentially three: the ritual one, the engineering one and the ethical one. With reference to the last category, classical ethical approaches to planning are those based on the principles of utilitarian (oriented to ensure efficiency and effectiveness for spatial changes), contractualist (oriented to pursue ends of social and environmental equity) and dialogical type (oriented to define planning ends in a public fair dialogue). But these ethical approaches seem inadequate, in their pure forms, to respond to policy-making requirements in our complex urban and regional societies. A really effective and fair system of spatial planning should instead respond not only to situations where ends and means are clear and well-defined but also to situations where there is strong conflict as regards the ends and to situations – perhaps the most frequent ones – where both ends and means are at the same time uncertain. From this standpoint it would seem that experiences (with particular reference to the Italian context) tending towards mixed and plural planning systems, should be regarded with interest. In this perspective, the contribution of the paper is finally addressed towards the definition of a mixed and plural, but loosely coupled, spatial planning system.

Multiparton scattering at the LHC

The large parton flux at high energy gives rise to events where different pairs of partons interact contemporarily with large momentum exchange. A main effect of multiple parton interactions is to generate events with many jets at relatively large transverse momenta. The large value of the heavy quarks production cross section may however give also rise a sizable rate of events with several $b$-quarks produced. We summarize the main features of multiparton interactions and make some estimate of the inclusive cross section to produce two $b{\bar b}$ pairs within the acceptance of the ALICE detector.Comment: 10 pages, 4 figures, contribution to ALICE PP

Cybernetical Concepts for Cellular Automaton and Artificial Neural Network Modelling and Implementation

As a discipline cybernetics has a long and rich history. In its first generation it not only had a worldwide span, in the area of computer modelling, for example, its proponents such as John von Neumann, Stanislaw Ulam, Warren McCulloch and Walter Pitts, also came up with models and methods such as cellular automata and artificial neural networks, which are still the foundation of most modern modelling approaches. At the same time, cybernetics also got the attention of philosophers, such as the Frenchman Gilbert Simondon, who made use of cybernetical concepts in order to establish a metaphysics and a natural philosophy of individuation, giving cybernetics thereby a philosophical interpretation, which he baptised allagmatic. In this paper, we emphasise this allagmatic theory by showing how Simondon's philosophical concepts can be used to formulate a generic computer model or metamodel for complex systems modelling and its implementation in program code, according to generic programming. We also present how the developed allagmatic metamodel is capable of building simple cellular automata and artificial neural networks.Comment: 12 pages, 1 figur

The Effects of Funding Costs and Risk on Banks' Lending Rates

After falling for over a decade, the major banks' net interest margins appear to have stabilised in a relatively narrow range in recent years. In the early part of the financial crisis, margins fell to the bottom of this range, reflecting an increase in debt funding costs. Margins have since recovered a little, to around the middle of the range, as a result of some repricing of lending rates relative to these costs. In addition to the increase in the cost of debt funding, there have been other drivers of the rise in lending rates relative to the cash rate. First, the banks have increased their equity funding, which is more costly than debt finance. Second, risk margins on loans have risen to account for higher expected losses.funding costs; lending rates; interest rates; risk pricing