LORENTZ INVARIANCE OF EFFECTIVE STRINGS

Starting from a Poincare-invariant field theory of a real scalar field with interactions governed by a double-well potential in 2+1 dimensions, the Lorentz representation induced on the collective coordinates describing low-energy excitations about an effective string background is derived. In this representation, Lorentz transformations are given in terms of an infinite series, in powers of derivatives along the world-sheet. Transformations.that act on the direction transverse to the string world-sheet involve a universal dimension -1 term. As a consequence, Lorentz invariance holds in this theory of long effective strings due to cancellations in the action between irrelevant terms and the dimension-2 term that describes free massless scalar fields in two dimensions.