We discuss Standard Model (SM) and New Physics (NP) descriptions of D0
mixing. The SM part of the discussion addresses both quark level and hadron
level contributions. The NP part describes our recent works on the rate
difference Delta Gamma_D and the mass difference Delta M_D. In particular, we
describe how the recent experimental determination of Delta M_D is found to
place tightened restrictions on parameter spaces for 17 of 21 NP models
considered in a recent paper by Hewett, Pakvasa, Petrov and myself.Comment: 6 pages, to be published in the proceedings of CHARM07, Ithaca, NY,
August 2007, eConf C07080
