Many numerical codes now under development to solve Einstein's equations of
general relativity in (3 + 1)-dimensional spacetimes employ the standard A
DM form of the held equations. This form involves evolution equations for t
he raw spatial metric and extrinsic curvature tensors. Following Shibata an
d Nakamura, we modify these equations by factoring out the conformal factor
and introducing three "connection functions." The evolution equations can
then be reduced to wave equations for the conformal metric components, whic
h are coupled to evolution equations for the connection functions. We evolv
e small amplitude gravitational waves and make a direct comparison of the n
umerical performance of the modified equations with the standard ADM equati
ons. We find that the modified form exhibits much improved stability. [S005
6-2821(98)08124-7].