A VIRIAL IDENTITY APPLIED TO RELATIVISTIC STELLAR MODELS

A two-dimensional integral identity is derived for a genera) asymptoti cally flat four-dimensional spacetime, providing a generalization of t he 'virial' identity obtained by Bonazzola for the stationary axisymme tric case. It is applied to show that some spatial component of the st ress-energy tensor must be positive in some (if not all) points of a s tatic stellar model. This identity has also proved to be useful for ch ecking numerical solutions of Einstein's equation describing rotating neutron stars.