Vacuum energy for the supersymmetric twisted D-brane in constant   electromagnetic field
  We calculate vacuum energy for twisted SUSY D-brane on toroidal background with constant magnetic or constant electric field. Its behaviour for toroidal D-brane (p=2) in constant electric field shows the presence of stable minimum for twisted versions of the theory. That indicates such a background maybe reasonable groundstate. 
A.A. Bytsenko, A.E. Goncalves, S. Nojiri and S.D. Odintsov