Perturbative two-loop quark potential of stiff strings in any dimension

We present a systematic perturbative calculation of the static quark-antiquark potential of stiff strings up to two loops. Our result is valid in any number of dimensions d. In particular we find that the string tension M02 is renormalized as follows: M2=M02[1+(1/2(d-2))(α0/4) (1+4πL)+(1/4d-2)(d-1)(α0L) 2], where α0 is the inverse stiffness of the string and L the logarithmic divergence L=(1/4π)ln(Λ2/μ2). At large distances, not only Luescher's 1/R term but also the 1/R3 term is found to be independent of the coupling strength