arXiv subjects

M. Cavicchi

Publications and source records attributed to M. Cavicchi.

3 recordsLinked to original sources

arXiv1994

A New Tool for the Lamb Shift Calculation

We solve the Bethe-Salpeter equation for hydrogenic bound states by choosing an appropriate interaction kernel $K_c$. We want to use our solution to calculate up to a higher order the hydrogen Lamb-shift, and as a first application we present up to order $\left(å/ π\right)(\za)^7$ the contribution of the lowest order self-energy graph, calculated {\it exactly}. The basic formalism is a natural extension to the hydrogenic bound states of the one previously presented by R. Barbieri and E. Remiddi and used in the case of positronium.

hep-ph↗

arXiv1994

A Bilocal Field Approach to the Large-N Expansion of Two-Dimensional (Gauge) Theories

We consider a wide class of two-dimensional models as gauge theories, Gross-Neveu model, $O(N)$ and $CP^{N-1}$-like models using a formalism based on the introduction of bilocal fields that permits to perform easily the large-N expansion of this set of models in a unified and general way. We mainly discuss the $SU(N)$ gauge field theory minimally coupled to fermionic plus bosonic matter in the fundamental representation, and we obtain within the path integral approach exact equations for the particle spectrum, also in presence of renormalizable polynomial potentials. Finally, we discuss the correspondence between this new approach and the one previously used in the context of the $O(N)$ vector models.

hep-th↗

arXiv1993

The Master Field of QCD$_2$ and the 'T Hooft Equation

We rewrite the action for $QCD_2$ in the light cone gauge only in terms of a bilocal mesonic field. In this formalism the $1/N$ expansion can be done in a straightforward way by a saddle point technique that determines the master field to be identified with the vacuum expectation value of the bilocal field. Finally we show that the equation of motion for the fluctuations around the master field is identical with the 't Hooft meson equation.

hep-th↗