The problem of uniqueness in the reduced description of adsorption on   the wedge-shaped substrate
  In the reduced one-dimensional description of the adsorption on the wedge-shaped substrate the mid-point interface height serves as the order parameter. We point at the ambiguity which appears in the transfer-matrix approach to this problem. We also propose how to avoid this problem by introducing the appropriate order parameter. 
A. Bednorz, M. Napiorkowski (Instytut Fizyki Teoretycznej, Uniwersytet   Warszawski)