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

Holographic Bound in Quantum Field Energy Density and Cosmological Constant

The cosmological constant problem is reanalyzed by imposing the limitation of the number of degrees of freedom (d.o.f.) due to entropy bounds directly in the calculation of the energy density of a field theory. It is shown that if a quantum field theory has to be consistent with gravity and holography, i.e. with an upper limit of storing information in a given area, the ultraviolet momentum cut-off is not the Planck mass, M_p, as naively expected, but M_p/N_U^(1/4) where N_U is the number of d.o.f. of the universe. The energy density evaluation turns out completely consistent with Bousso's bound on the cosmological constant value. The scale M_p/N_U^(1/4), that in the "fat graviton" theory corresponds to the graviton size, originates by a selfsimilar rearrangement of the elementary d.o.f. at different scales that can be seen as an infrared-ultraviolet connection.Comment: Submitted to PRD, more accurate reference