Quantum discord and noncontextual hidden variables models
  It is shown that theoretically viable noncontextual hidden variables models in $d=2$ lead to conflicting dispersion free expressions in the analysis of the conditional measurement of two non-orthogonal projectors.   No satisfactory criterion of the quantum discord, which relies on the analysis of conditional measurement, is formulated in the $d=2$ hidden variables space due to a lack of uniqueness of the dispersion free representation.   We also make a speculative comment on a "many-worlds interpretation" of hidden variables models to account for the conditional measurement. 
Kazuo Fujikawa
quant-ph