Energetic model of tumor growth

A macroscopic model of the tumor Gompertzian growth is proposed. This approach is based on the energetic balance among the different cell activities, described by methods of statistical mechanics and related to the growth inhibitor factors. The model is successfully applied to the multicellular tumor spheroid data.Comment: 5 pages, 2 figures, contribution to "Complexity, Metastability and Nonextensivity", Erice, July 200

Symmetry breaking in non-commutative cut-off field theories

The relation between symmetry breaking in non-commutative cut-off field theories and transitions to inhomogeneous phases in condensed matter and in finite density QCD is discussed. The non-commutative dynamics, with its peculiar infrared-ultraviolet mixing, can be regarded as an effective description of the mechanisms which lead to inhomogeneous phase transitions and a roton-like excitation spectrum.Comment: LaTex, 3 pages,Talk given at "Quark Confinement and the Hadron Spectrum VI", 21-25 September 2004, Villasimius, Ital

Early Labour Market Returns to College Subjects

This paper aims at estimating early labour market outcomes of Italian university graduates across college subjects. We devote great attention to endogenous selection issues using alternative methods to control for potential self-selection associated with the choice of the degree subject in order to unravel the causal link between college major and subsequent outcomes in the labour market. Our results suggest that “quantitative” fields (i.e. Sciences, Engineering and Economics) increase not only the speed of transition into the first job and employment probability but also early earnings, conditional on employment.University to work transition; College subject; Self-selection; Returns to education

Indications of a Pseudogap in the Nambu Jona-Lasinio model

The survival of \bar q q bound states at temperatures higher than the chiral restoration temperature, T_c, recently observed in lattice QCD, is discussed in the framework of the Nambu Jona-Lasinio model. The perturbative determination of the spectral function provides an indication of a pseudogap phase above T_c.Comment: Contributed to the International Workshop: QCD@Work 2005, Conversano, Bari, Italy, 16-20 Jun 200

Variance reduction in MCMC

We propose a general purpose variance reduction technique for MCMC estimators. The idea is obtained by combining standard variance reduction principles known for regular Monte Carlo simulations (Ripley, 1987) and the Zero-Variance principle introduced in the physics literature (Assaraf and Caffarel, 1999). The potential of the new idea is illustrated with some toy examples and an application to Bayesian estimationMarkov chain Monte carlo, Metropolis-Hastings algorithm, Variance reduction, Zero-Variance principle

Nuclear density functional constrained by low-energy QCD

We have developed a relativistic point-coupling model of nuclear many-body dynamics constrained by the low-energy sector of QCD. The effective Lagrangian is characterized by density-dependent coupling strengths determined by chiral one- and two-pion exchange (with single and double delta isobar excitations) and by large isoscalar background fields that arise through changes of the quark condensate and the quark density at finite baryon density. The model has been tested in the analysis of nuclear ground-state properties along different isotope chains of medium and heavy nuclei. The agreement with experimental data is comparable with purely phenomenological predictions. The built-in QCD constraints and the explicit treatment of pion exchange restrict the freedom in adjusting parameters and functional forms of density-dependent couplings. It is shown that chiral pionic fluctuations play an important role for nuclear binding and saturation mechanism, whereas background fields of about equal magnitude and opposite sign generate the effective spin-orbit potential in nuclei.Comment: ws-procs9x6.cls, 8 pgs, Talk presented at "X Convegno su Problemi di Fisica Nucleare Teorica", Cortona (AR), 6-9 october 200