On the rigid string contribution to the interquark potential

Owing to Lorentz invariance, the leading terms in the effective action describing the low-energy dynamics of flux tubes in a confining gauge theory are universal. Besides the terms corresponding to the Nambu-Goto action, Lorentz invariance also allows terms describing a "rigid string", proposed long ago by Kleinert and Polyakov as a model for confinement in a dual superconductor scenario. In this contribution we discuss some of the non-trivial properties of this type of string and evaluate analytically the corrections to the interquark potential induced by extrinsic curvature terms appearing in the rigid string action.