Mathisson-Papapetrou equations in metric and gauge theories of gravity in a Lagrangian formulation

We present a simple method to derive the semiclassical equations of motion for a spinning particle in a gravitational field. We investigate the cases of classical, rotating particles (pole-dipole particles), as well as particles with intrinsic spin. We show that, starting with a simple Lagrangian, one can derive equations for the spin evolution and momentum propagation in the framework of metric theories of gravity and in theories based on a Riemann-Cartan geometry (Poincare gauge theory), without explicitly referring to matter current densities (spin and energy-momentum). Our results agree with those derived from the multipole expansion of the current densities by the conventional Papapetrou method and from the WKB analysis for elementary particles.Comment: 28 page

Pleba\'nski-Demia\'nski-like solutions in metric-affine gravity

We consider a (non--Riemannian) metric--affine gravity theory, in particular its nonmetricity--torsion sector ``isomorphic'' to the Einstein--Maxwell theory. We map certain Einstein--Maxwell electrovacuum solutions to it, namely the Pleba\'nski--Demia\'nski class of Petrov type D metrics.Comment: 12 pages of a LaTeX-fil

Guida alla redazione degli atti amministrativi

La "Guida alla redazione degli atti amministrativi" intende fornire indicazioni per la redazione degli atti per tutti i funzionari della pubblica amministrazione. Si articola in tre parti: (a) la lingua degli atti, (b) la struttura del provvedimento amministrativo, (c) il rinvio ad altri atti. Ne è autore un gruppo di linguisti e giuristi facenti capo all'ITTIG-CNR (Istituto per le Tecniche e Tecnologie dell'Informazione Giuridica) e dell'Accademia della Crusca

Minimal coupling of electromagnetic field in Riemann-Cartan spacetime for perfect fluids

We minimally couple the electromagnetic field to gravity in Riemann-Cartan spacetime in the self-consistent formalism for perfect fluids by treating the internal energy of matter as a function of the electromagnetic field. The overall Lagrangian of the gravitational field, perfect fluid, and the electromagnetic field is constrained to be gauge invariant under gauge transformations of the vector potential. The theory preserves both charge conservation and particle number conservation, and gives the usual form of the free field equations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44578/1/10773_2004_Article_BF00673926.pd