Representations of the Schr\"odinger group and matrix orthogonal   polynomials
  The representations of the Schr\"odinger group in one space dimension are explicitly constructed in the basis of the harmonic oscillator states. These representations are seen to involve matrix orthogonal polynomials in a discrete variable that have Charlier and Meixner polynomials as building blocks. The underlying Lie-theoretic framework allows for a systematic derivation of the structural formulas (recurrence relations, difference equations, Rodrigues' formula etc.) that these matrix orthogonal polynomials satisfy. 
Luc Vinet and Alexei Zhedanov
math-ph math.MP