The physical projector and topological quantum field theories: U(1) Chern-Simons theory in 2+1 dimensions

The recently proposed physical projector approach to the quantization of gauge-invariant systems is applied to the U(1) Chern-Simons theory in 2+1 dimensions as one of the simplest examples of a topological quantum field theory. The physical projector is explicitly demonstrated to be capable of effecting the required projection from the initially infinite number of degrees of freedom to the finite set of gauge-invariant physical states whose properties are determined by the topology of the underlying manifold. (author)