M-theory lift of brane-antibrane systems and localised closed string   tachyons
  We discuss the lift of certain D6-antiD6-brane systems to M-theory. These are purely gravitational configurations with a bolt singularity. When reduced along a trivial circle, and for large bolt radius, the bolt is related to a non-supersymmetric orbifold type of singularity where some closed string tachyons are expected in the twisted sectors. This is a kind of open-closed string duality that relates open string tachyons on one side and localised tachyons in the other. We consider the evolution of the system of branes from M-theory point of view. This evolution gives rise to a brane-antibrane annihilation on the brane side. On the gravity side, the evolution is related to a reduction of the order of the orbifold and to a contraction of the bolt to a nut or flat space if the system has non-vanishing or vanishing charge, respectively. We also consider the inverse process of reducing a non-supersymmetric orbifold to a D6-brane system. For $C^2/Z_N\times Z_M$, the reduced system is a fractional D6-brane at an orbifold singularity $C/Z_M$. 
Raul Rabadan and Joan Simon