Limits to the scope of applicability of extended formulations for LP   models of combinatorial optimization problems: A summary
  We show that new definitions of the notion of "projection" on which some of the recent "extended formulations" works (such as Kaibel (2011); Fiorini et al. (2011; 2012); Kaibel and Walter (2013); Kaibel and Weltge (2013) for example) have been based can cause those works to over-reach in their conclusions in relating polytopes to one another when the sets of the descriptive variables for those polytopes are disjoint. 
Moustapha Diaby and M. H. Karwan
cs.CC cs.DM math.OC