Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields 

About: Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields is an academic journal. The journal publishes majorly in the area(s): Meson & Scattering. Over the lifetime, 8417 publications have been published receiving 58934 citations.

A PCAC puzzle: π0→γγ in the σ-model

Abstract: The effective coupling constant for π0→γγ should vanish for zero pion mass in theories with PCAC and gauge invariance. It does not so vanish in an explicit perturbation calculation in the σ-model. The resolution of the puzzle is effected by a modification of Pauli-Villars-Gupta regularization which respects both PCAC and gauge invariance.

Conformal Invariance in Quantum Mechanics

Abstract: The properties of a field theory in one over-all time dimension, invariant under the full conformal group, are studied in detail. A compact operator, which is not the Hamiltonian, is diagonalized and used to solve the problem of motion, providing a discrete spectrum and normalizable eigenstates. The role of the physical parameters present in the model is discussed, mainly in connection with a semi-classical approximation.

Gravitation and quantum mechanics of macroscopic objects

Abstract: The problem of the reduction of the wave function in quantum theory is treated from a new standpoint. First, by combining Heisenberg's uncertainty relations with gravitation, quantitative limi tations on the sharpness of the structure of space-time are derived. Second, the resulting uncertainty in space-time structure is incorporated into the equations for the propagation of the quantum-mechanical wave amplitudes. In the resulting theory an initially pure wave function generally develops in time into a mixture. A single pure wave function survives only as long as it corresponds to a sufficiently small spread in the position of any massive part of the system under investigation. Quantitative relations between the mass and the maximum coherent spread in the center-of-mass wave function of a single body are obtained.

Differential equations for Feynman graph amplitudes

Abstract: It is by now well established that, by means of the integration by part identities, all the integrals occurring in the evaluation of a Feynman graph of given topology can be expressed in terms of a few independent master integrals. It is shown in this paper that the integration by part identities can be further used for obtaining a linear system of first-order differential equations for the master integrals themselves. The equations can then be used for the numerical evaluation of the amplitudes as well as for investigating their analytic properties, such as the asymptotic and threshold behaviours and the corresponding expansions (and for analytic integration purposes, when possible). The new method is illustrated through its somewhat detailed application to the case of the one-loop self-mass amplitude, by explicitly working out expansions and quadrature formulas, both in arbitrary continuous dimensionn and in then→4 limit. It is then shortly discussed which features of the new method are expected to work in the more general case of multi-point, multi-loop amplitudes.