Algebraically special solutions in AdS/CFT

We investigate the AdS/CFT interpretation of the class of algebraically special solutions of Einstein gravity with a negative cosmological constant. Such solutions describe a CFT living in a 2+1 dimensional time-dependent geometry that, generically, has no isometries. The algebraically special condition implies that the expectation value of the CFT energy-momentum tensor is a local function of the boundary metric. When such a spacetime is slowly varying, the fluid/gravity approximation is valid and one can read off the values of certain higher order transport coefficients. To do this, we introduce a formalism for studying conformal, relativistic fluids in 2+1 dimensions that reduces everything to the manipulation of scalar quantities.Comment: 30 pages + appendices, 2 figures; v2: typos corrected, ref. adde

Spectral-based k-corrections and implications for the colour-magnitude relation of E/S0s and its evolution

We select a sample of 70378 E/S0 (early-type) galaxies at 0<z<0.36 from the Sloan Digital Sky Survey, excluding disk and star-forming galaxies. We estimate g and r magnitudes in the observer- and rest-frames directly from the SDSS DR6 spectra; this provides an object-by-object estimate of the k-correction. We use the k-corrections from the spectra to study the evolution of the rest-frame colour-magnitude relation (CMR) and colour-sigma (velocity dispersion) relation (CsigmaR). The evolution is very sensitive to the k-correction. Both the CMR and CsigmaR evolve blueward with increasing redshift, approximately in agreement with passive evolution models with age approx. 12 Gyr. The slope and zero-point of the CMR depend on whether colours were defined in fixed physical or angular apertures, a consequence of the fact that the centers of these objects tend to be redder: the relation is steeper for fixed angular apertures. One the other hand, the CsigmaR slope does not show this dependence on the aperture in which the colour was defined, suggesting that colour gradients are correlated with residuals from the sigma-M_r relation. As these residuals are age indicators, our findings suggest that colour gradients correlate with the age of the stellar population.Comment: 16 pages, 24 figures, accepted for publication in MNRAS (minor revisions and 3 new figures added following referees comments

The effect of the environment on the Faber Jackson relation

We investigate the effect of the environment on the Faber Jackson (FJ) relation, using a sample of 384 nearby elliptical galaxies and estimating objectively their environment on the typical scale of galaxy clusters. We show that the intrinsic scatter of the FJ is significantly reduced when ellipticals in high density environments are compared to ellipticals in low density ones. This result, which holds on a limited range of overdensities, is likely to provide an important observational link between scaling relations and formation mechanisms in galaxies.Comment: accepted by Ap

OTTIMIZZAZIONE DEL PROCESSO DI PHASE - OUT PER AEROMOBILI DELL'AVIAZIONE CIVILE IN MANUTENZIONE

SOMMARIO Questo lavoro di tesi, a seguito di un periodo di stage presso Meridiana Maintenance Srl, sviluppa una proposta per far fronte ad una reale esigenza delle compagnie aeree che, servendosi del Dry Leasing per lo svolgimento delle proprie attività, si trovano nella necessità di riconsegnare al Lessor l’aeromobile e la relativa documentazione al termine del periodo di leasing, secondo canoni contrattuali ben precisi (processo di Phase-Out). Da qui l’idea di applicare la metodologia di Project Management a tale processo, in quanto essa consente la gestione sistematica del progetto mediante un processo continuo di pianificazione e controllo di differenti risorse, con vincoli interdipendenti di costi - tempi - qualità. Sono state raggiunte alcune ipotesi di risultato con la proposta di possibili azioni preventive sul lavoro da svolgere nella gestione della documentazione. Frutto dell’analisi complessiva sviluppata è stato quello di individuare gli effetti che tali azioni preventive hanno sulla gestione totale del progetto