STRING TENSION AND THE GENERATION OF THE CONFORMAL ANOMALY - ART. NO.047901

The origin of the string conformal anomaly is studied in detail. We us e a reformulated string Lagrangian which allows us to consider the str ing tension T-0 as a small perturbation. The expansion parameter is th e world-sheet speed of light c, which is proportional to T-0. We exami ne carefully the interplay between a null (tensionless) string and a t ensionful string which includes orders c(2) and higher. The conformal algebra generated by the constraints is considered. At the quantum lev el the normal ordering provides a central charge proportional to c(2). Thus it is clear that quantum null strings respect conformal invarian ce and it is the string tension which generates the conformal anomaly.