Comment on ``Integrability and Coherence of Hopping between 1D   Correlated Electron Systems''
  We comment on recent numerical studies concerning coupled 1D electron liquids (F. Mila and D. Poilblanc, Phys. Rev. Lett. 76, 287 (1996)). In particular, we point out that the importance of integrability observed in the results of these authors for the quantity $P(t)$ is really an indication of the importance of integrability for questions of ergodicity, rather than questions of coherence. We discuss why this is so, and why the quantity $< \delta N (t) >$ is a more appropriate function for determining whether or not interliquid hopping is coherent. 
David Clarke (Princeton) and Steven Strong (IAS, Princeton)