Perturbative method to solve fourth-order gravity field equations.

We reconsider the cosmic string perturbative solution to the classical fourthorder gravity field equations, obtained in Ref. [1], and we obtain that static, cylindricaly symmetric gauge cosmic strings, with constant energy density, can contain only β-terms in the first order corrections to the interior gravitational field, while the exact exterior solution is a conical spacetime with deficit angle D = 8πμ. 04.50.+h, 11.27.fd Typeset using REVTEX