Closed bosonic strings in a covariant phase space

In a covariant phase space the Poisson bracket Lie algebra of (1+1)-dimensional diffeomorphisms has a three-parameter family of Lorentz- and translation-invariant local string representations. In the second-quantized string theory these parameters appear in the Schwinger term of the commutator algebra and modify the critical dimension, and in the lagrangian formulation they contribute to frame anomalies associated with functional determinants.