The Geometry of Interaction of Differential Interaction Nets

The Geometry of Interaction purpose is to give a semantic of proofs or programs accounting for their dynamics. The initial presentation, translated as an algebraic weighting of paths in proofnets, led to a better characterization of the lambda-calculus optimal reduction. Recently Ehrhard and Regnier have introduced an extension of the Multiplicative Exponential fragment of Linear Logic (MELL) that is able to express non-deterministic behaviour of programs and a proofnet-like calculus: Differential Interaction Nets. This paper constructs a proper Geometry of Interaction (GoI) for this extension. We consider it both as an algebraic theory and as a concrete reversible computation. We draw links between this GoI and the one of MELL. As a by-product we give for the first time an equational theory suitable for the GoI of the Multiplicative Additive fragment of Linear Logic.Comment: 20 pagee, to be published in the proceedings of LICS0

NA60 results on phi production in the hadronic and leptonic channels in In-In collisions at 158 GeV

The NA60 experiment at the CERN SPS studied phi meson production in In-In collisions at 158 A GeV via muon and kaon decay channels. Results in the hadronic channel are presented for the first time. These are discussed in the framework of the so-called phi puzzle through the comparison with the previous NA60 measurements in the muon channel. The yield and inverse m_T slopes observed in the two channels are compatible within errors, showing that the large discrepancies seen in Pb-Pb collisions between NA50 (muon pairs) and NA49 (kaon pairs) are not seen in the NA60 In-In data.Comment: 4 pages, 4 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Doctoral Education in Planning and Urban Studies in Italy: what is it really for? Introduction and Editorial note

Data show the reduction of academic positions in Italy and invite to reconsider the role of PhD education and training as the highest level of university education. In fact, although PhDs seem to have a little advantage over Master’s level graduates in the job market, only about 10% find a job at universities. This suggests that changes in PhD programmes might be needed to match students’ needs and job market requirements. However, the opposite is also true with employers, either in the public or private sector, who should try to absorb more PhDs and use their skills and expertise. The aim of this special issue is to analyse PhD education in Italy with a focus on planning and urban studies programmes by emphasising the perspectives of PhD candidates and freshly awarded Doctors since they are generally neglected in reform processes. All authors who contributed to this special issue reflected on the same aim stressing different implications and perspectives. The topics investigated are: matching between students’ expectations and institutional goals, the international mobility of PhD candidates, experiences of international PhD students in Italy, and the evolution of two of the oldest PhD programmes in planning in Italy at Sapienza, Rome and Iuav, Venice

A study of the effects of Lebu devices on turbulent boundary layer drag

Initial measurements of the changes in local skin friction, velocity profile shape, and turbulence structure which result from the placement of tandem plates parallel to the wall in the outer region of thick turbulent boundary layers were made. Using a tunnel with a .75 m x 1.2 m x 7.3 m test section, which diverged so as to keep the pressure gradient less than 2x1000/ft, on the test wall, a skin friction reduction of approximately 30% was measured at xi/h = 62. This relaxed to a reduction of approximately 16% at xi/h = 124 for h/delta M = .6. The c sub f measurements for both the normal and modified boundary layers were obtained by measuring the slope of the velocity profile within the linear sublayer. Visual results indicated a continued presence of strong large eddy structure downstream of the devices. Local skin friction reduction of 12% at xi/h = 62 was also obtained with the manipulators above the boundary layer at y/delta m = 1.1