In four spacetime dimensions, N = 8 supergravity, speculated by Stephen Hawking, is the most symmetric quantum field theory which involves gravity and a finite number of fields.
It can be found from a dimensional reduction of eleven-dimensional supergravity by making the size of seven of the dimensions go to zero.
There has been renewed interest in the 21st century, with the possibility that this theory may be finite.
This is written schematically as: This is not surprising, as N = 8 supergravity contains six independent representations of N = 4 super Yang–Mills.
For model building, it has been assumed that almost all the supersymmetries would be broken in nature,[why?]