Abstract. The initial data of the gravitational field produced by a thick loop string are considered. We show that a thick loop is not a geodesic on the initial hypersurface, while a loop conical singularity is. This suggests that there is a 'critical thickness' of a string, at which the linear perturbation theory with a flat space background fails to describe the gravity of a loop cosmic string. Using the above initial data, we also show that the linear perturbation around the flat space is plausible if the string thickness is larger than ~5 × 10⁻³a, where a is the curvature radius of the loop.

PACS numbers: 0420E, 0440, 1127, 9880C

Print publication: Issue 4 (21 February 2002)
Received 17 August 2001, in final form 18 December 2001
Published 6 February 2002