R symmetries and a heterotic MSSM
  We employ powerful techniques based on Hilbert- and Groebner bases to analyze particle physics models derived from string theory. Individual models are shown to have a huge landscape of vacua that differ in their phenomenological properties. We explore the (discrete) symmetries of these vacua, the new R symmetry selection rules and their consequences for moduli stabilization. 
Rolf Kappl, Hans Peter Nilles, Matthias Schmitz
hep-ph hep-th