Symmetry reduced Einstein gravity and generalized sigma and chiral models
arXiv:gr-qc/9712053 · doi:10.1142/S0218271898000371
Abstract
Certain features associated with the symmetry reduction of the vacuum Einstein equations by two commuting, space-like Killing vector fields are studied. In particular, the discussion encompasses the equations for the Gowdy cosmology and cylindrical gravitational waves. We first point out a relation between the (or SO(3)) and principal chiral models, and then show that the reduced Einstein equations can be obtained from a dimensional reduction of the standard SL(2,R) sigma-model in three dimensions. The reduced equations can also be derived from the action of a `generalized' two dimensional SL(2,R) sigma-model with a time dependent constraint. We give a Hamiltonian formulation of this action, and show that the Hamiltonian evolution equations for certain phase space variables are those of a certain generalization of the principal chiral model. Using these Hamiltonian equations, we give a prescription for obtaining an infinite set of constants of motion explicitly as functionals of the space-time metric variables.
17 pages, latex, reference added, a subtlety commented on; to appear in Int. J. Mod. Phys. D