Effective action and tension renormalization for cosmic and fundamental strings

We derive the effective action for classical strings coupled to dilatonic, gravitational, and axionic fields. We show how to use this effective action for: (i) renormalizing the string tension, (ii) linking ultraviolet divergences to the infrared (long-range) interaction between strings, (iii) bringing additional light on the special cancellations that occur for fundamental strings, and (iv) pointing out the limitations of Diracʹs celebrated field-energy approach to renormalization.