Absence of stress energy tensor in CFT_2 models

Abstract

We prove: the quantum field theories defined by conformally covariant derivatives of the U(1)-current algebra in 1+1 dimensions do not contain a stress energy tensor in the sense of the theorem of Luescher and Mack.

Argument leading to main result simplyfied now; contents of section 2 of v1 are now part of math-ph/0312017; 8 pages, no figures