M-theory low energy limit is eleven-dimensional supergravity. However I understand that Itzhak Bars and others have been working in generalizations of string theories of 12, 13 and 14 dimensions with signatures (10,2), (10,3) or (11,3).
There is the obvious problem that supergravity is believed to can be formulated in a maximum number of 11 dimensions owing to the impossibility of a consistent interacting theory in Minkowski spacetime with massless particles of spin>2.
Does anybody know about how this problem is circumnavigated in Bars's theory (and in other attempts of constructing supergravity theories with $D>11$)?
Edit: Some of the related Bars's papers https://arxiv.org/abs/hep-th/9704054 or https://arxiv.org/abs/hep-th/9607112v1
