On the two approaches to the data analysis of the Cassini interplanetary relativity experiment

We compare two theoretical approaches to the data analysis of the Cassini relativity experiment based on the Doppler tracking and the time delay technique that were published correspondingly by Kopeikin et al in Phys. Lett. A 367, 276 (2007) and by Bertotti et al in Class. Quant. Grav. 25, 045013 (2008). Bertotti et al believed that they found a discrepancy with our paper and claimed that our analysis was erroneous. The present paper elucidates, however, that the discrepancy is illusory and does not exist. The two techniques give the same result making it evident that the numerical value of the PPN parameter 'gamma' measured in the Cassini experiment is indeed affected by the orbital motion of the Sun around the barycenter of the solar system.Comment: 6 pages, no figures. Accepted for publication to Physics Letters

Economic competitiveness and governance in areas of urban deprivation: the case study of two growth strategies in London.

In an urban context characterised by concentrated and persistent deprivation there has been a history of policy intervention albeit with limited impact. Michael Porter's US inspired City Growth Strategy (CGS) initiative presented an alternative approach to urban economic regeneration within the UK characterised by a focus on the competitive advantages of deprived urban areas and a leading role for the private sector within the policy making process. This thesis investigates the implementation of the City Growth Strategy in two areas of London (Haringey and the City Fringe) to explore wider issues of economic competitiveness and governance in relation to deprived urban areas. Drawing upon a range of institutional, regulationist and policy networks theoretical perspectives, this research adopted a case study qualitative approach based on a number of face-to-face interviews. An evaluation process based on implementation theory was used to unpack the differences between theory, policy and practice with an emphasis on uncovering policy-making processes. The study found that the application of Porter's vision in the UK context displays a number of weaknesses rooted both in its conceptualisation of the problems of deprived urban areas and the nature of its implementation. The emphasis upon the competitive advantages of deprived urban areas largely failed to translate into effective interventions due to problems of operationalising cluster policy locally, a lack of appreciation of the social dimension to urban problems and the particularities of the UK context. Private sector engagement has remained weak, although with notable exceptions in certain sectors and contexts, constrained by the limited local interaction with the public sector and wider issues related to the continued dominance of the central state in setting and funding the policy agenda. Implications from these fìndings are discussed including the need to think more precisely about différent types and styles of private sector involvement

Mathematical models describing the effects of different tax evasion behaviors

Microscopic models describing a whole of economic interactions in a closed society are considered. The presence of a tax system combined with a redistribution process is taken into account, as well as the occurrence of tax evasion. In particular, the existence is postulated, in relation to the level of evasion, of different individual taxpayer behaviors. The effects of the mentioned different behaviors on shape and features of the emerging income distribution profile are investigated qualitatively and quantitatively. Numerical solutions show that the Gini inequality index of the total population increases when the evasion level is higher, but does not depend significantly on the evasion spread. For fixed spread, the relative difference between the average incomes of the worst evaders and honest taxpayers increases approximately as a quadratic function of the evasion level.Comment: To appear in J. of Economic Interaction and Coordinatio

Accurate light-time correction due to a gravitating mass

This work arose as an aftermath of Cassini's 2002 experiment \cite{bblipt03}, in which the PPN parameter $\gamma$ was measured with an accuracy $\sigma_\gamma = 2.3\times 10^{-5}$ and found consistent with the prediction $\gamma =1$ of general relativity. The Orbit Determination Program (ODP) of NASA's Jet Propulsion Laboratory, which was used in the data analysis, is based on an expression for the gravitational delay which differs from the standard formula; this difference is of second order in powers of $m$ -- the sun's gravitational radius -- but in Cassini's case it was much larger than the expected order of magnitude $m^2/b$, where $b$ is the ray's closest approach distance. Since the ODP does not account for any other second-order terms, it is necessary, also in view of future more accurate experiments, to systematically evaluate higher order corrections and to determine which terms are significant. Light propagation in a static spacetime is equivalent to a problem in ordinary geometrical optics; Fermat's action functional at its minimum is just the light-time between the two end points A and B. A new and powerful formulation is thus obtained. Asymptotic power series are necessary to provide a safe and automatic way of selecting which terms to keep at each order. Higher order approximations to the delay and the deflection are obtained. We also show that in a close superior conjunction, when $b$ is much smaller than the distances of A and B from the Sun, of order $R$, say, the second-order correction has an \emph{enhanced} part of order $m^2R/b^2$, which corresponds just to the second-order terms introduced in the ODP. Gravitational deflection of the image of a far away source, observed from a finite distance from the mass, is obtained to $O(m^2)$.Comment: 4 figure