2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100727We analyse the spectrum of the D-dimensional Poincare invariant effective string model of Polchinski and Strominger. It is shown that the leading terms beyond the Casimir term in the long distance expansion of the spectrum have a universal character which follows from the constraint of Poincare invariance.6 pages. Typos corrected, some clarifying remarks addedHigh Energy Physics - TheoryHigh Energy Physics - Latticetext