Full three-body problem in effective-field-theory models of gravity

Recent work in the literature has studied the restricted three-body problem within the framework of effective-field-theory models of gravity. This paper extends such a program by considering the full three-body problem, when the Newtonian potential is replaced by a more general central potential which depends on the mutual separations of the three bodies. The general form of the equations of motion is written down, and they are studied when the interaction potential reduces to the quantum-corrected central potential considered recently in the literature. A recursive algorithm is found for solving the associated variational equations, which describe small departures from given periodic solutions of the equations of motion. Our scheme involves repeated application of a 2 x 2 matrix of first-order linear differential operators.Comment: 23 pages, 1 figure, Revtex4. In the final version, Section VII is much longer, the misprints have been amended, and new References have been include

Architecture-based Qualitative Risk Analysis for Availability of IT Infrastructures

An IT risk assessment must deliver the best possible quality of results in a time-effective way. Organisations are used to customise the general-purpose standard risk assessment methods in a way that can satisfy their requirements. In this paper we present the QualTD Model and method, which is meant to be employed together with standard risk assessment methods for the qualitative assessment of availability risks of IT architectures, or parts of them. The QualTD Model is based on our previous quantitative model, but geared to industrial practice since it does not require quantitative data which is often too costly to acquire. We validate the model and method in a real-world case by performing a risk assessment on the authentication and authorisation system of a large multinational company and by evaluating the results w.r.t. the goals of the stakeholders of the system. We also perform a review of the most popular standard risk assessment methods and an analysis of which one can be actually integrated with our QualTD Model

Itinerant and localized states in strongly correlated systems by a modified mean-field slave-boson approach

The standard mean field slave-boson solution for the infinite-$U$ Hubbard model is revised. A slightly modified version is proposed which includes properly the incoherent contribution of the localized states. In contrast to the standard mean field result, this new proposed solution defines a unique spectral function to be used in the calculation of local and not local quantities, and satisfies the correct thermodynamic relations. The same approach is applied also to the mean field approximation in terms of Hubbard operators. As a byproduct of this analysis, Luttinger's theorem is shown to be fulfilled in a natural way.Comment: 2 eps figure enclosed, IJMP B style, accepted for publication on Int. Journ. Mod. Phys.

Location in a vertically differentiated industry

We analyze a model of a vertically differentiated duopoly with two regions. These two locations differ for the market size or for the distribution of the willingness to pay for quality of their consumers. Firms sequentially choose to settle in one region and then simultaneously compete in prices, selling their products both on the local market and on the foreigner one. We show that the decision whether to agglomerate or not crucially depends on the extent of regions’ asymmetries, but, counter intuitively, there are parametric configurations in which the model predicts that the leader (the first firm choosing location) settles either in the poorer or in the smaller region, leaving the other one to the follower.. Welfare analysis completes the paper.Regions; Vertical Differentiation; Oligopoly

An effective-gravity perspective on the Sun-Jupiter-comet three-body system

Within the solar system, approximate realizations of the three-body problem occur when a comet approaches a planet while being affected mainly by such a planet and the Sun, and this configuration was investigated by Tisserand within the framework of Newtonian gravity. The exact relativistic treatment of the problem is not an easy task, but the present paper develops an approximate calculational scheme which computes for the first time the tiny effective-gravity correction to the equation of the surface for all points of which it is equally advantageous to regard the heliocentric motion as being perturbed by the attraction of Jupiter, or the jovicentric motion as being perturbed by the attraction of the Sun. This analysis completes the previous theoretical investigations of effective-gravity corrections to the Newtonian analysis of three-body systems, and represents an intermediate step towards relativistic effects on cometary motions.Comment: Published versio

The Vegetation of S'Ena Arrubia lagoon (centre-western Sardinia)

This study describes the vegetation of S'Ena Arrubia lagoon, in the Gulf of Oristano, in the centre-western coast of Sardinia. This lagoon is classified as: Special Protection Zone (S.P.Z.) according to EEC Directive 79/409, community importance site according to EEC Directive 92/43, I.B.A. (Important Birds Area) site and fixed oasis of fauna protection and natural reserve. Throughout the years it was subject to several alterations. The most important ones were carried out in the Seventies and allowed the marine water upwelling and the fast removal of freshwater coming from the watershed. Before the fulfilment of these interventions, lagoon waters had a low salinity, as demonstrated by previous vegetation studies that showed the presence of freshwater communities and, only to a smaller extent, of halo-tolerant and halophile ones. This phytosociologic study led to the identification of several associations that are showed in the groups of merely halophile vegetation, in the freshwater and subhalophile lagoon vegetation and in the merely anthropogen vegetation typologies. The location of the considered typologies is represented with distributive patterns, which synthesise the current state of vegetation referring to the salinity. Two new associations, the Inulo crithmoidis-Paspaletum vaginati and the Astero tripolii-Bolboschoenetum maritimi, are here described. The first is dominated by the presence of Paspalum vaginatum Swartz, recorded for the second time in Italy and for the first time in Sardinia. It is recorded near the inlet, where it forms mosaics together with Salicornietum emerci association and it is also present, as bolboschoenetosum maritimi subassociation, in more inland and less salty zones. The latter new association includes the subhalophile reedswamps that are present in the areas floodcd by salty waters for a long time, where it replaces the Scirpetum compacto-littoralis, a less halophile association present in several siles of the Mediterranean and also in Sardinia. In addition, it is necessary to point out the recovery of Salicornietum venetae association, characterised by the presence of Salicornia veneta Pign. et Lausi, which was believed endemic in the North Adriatic lagoons. Finally, the significance of environmental changes fulfilled in the basin, which are the reason for some vegetation modifications and are detected by comparison between current associations and those at the beginning of the Seventies, is pointed out