On Spectrum Generating Algebra of the Heun Operator
  The Heun operator has been cast, in terms of the elements of an underlying $su(1,1)$ algebra, under specific parametric conditions, for the purpose of spectrum generation. These elements are differential operators of \emph{degrees} $\pm 1/2$ and $0$. It is found that the regular singularities at $0$ and $\infty$ of the general Heun equation must be \emph{elementary} under the required parametric conditions. The spectrum generation has been demonstrated through a set of examples. 
Priyasri Kar, Ritesh K. Singh, Ananda Dasgupta and Prasanta K.   Panigrahi
quant-ph gr-qc hep-th math-ph math.MP