Phase Ordering of 2D XY Systems Below T_{KT}

We consider quenches in non-conserved two-dimensional XY systems between any two temperatures below the Kosterlitz-Thouless transition. The evolving systems are defect free at coarse-grained scales, and can be exactly treated. Correlations scale with a characteristic length L ( t ) ∝ t 1 / 2 at late times. The autocorrelation decay exponent, ¯ λ = ( η i + η f ) / 2, depends on both the initial and the final state of the quench through the respective decay exponents of equilibrium correlations, C EQ ( r ) ∼ r − η . We also discuss time-dependent quenches.