  Parametrized field theories, which are generally covariant versions of
ordinary field theories, are studied from the point of view of the covariant
phase space: the space of solutions of the field equations equipped with a
canonical (pre)symplectic structure. Motivated by issues arising in general
relativity, we focus on: phase space representations of the spacetime
diffeomorphism group, construction of observables, and the relationship between
the canonical and covariant phase spaces.
