N=8 Supergravity: Maximal Supergravity Explained

[isospin]

Provided that no particles have spins higher than 2, maximal supergravities are defined to be with supergravities with 32 supersymmetries.
Why is the N=8 supergravity in four dimensions called 'the maximal supergravity'? I am confused now...
Thanks.

 

[xepma]

Not an expert, but from what I've been told the N>8 supergravity theories always contain particles with spin > 2. And these are not well-defined.

 

[isospin]

Thanks for your reply. However, I am not sure whether it's right.
Another answer, which may be wrong, is that in four dimensions the spinors are 4-dimensional, then one could obtain 4*8=32 for the N=8 case.
But what does it mean, and why Is it in accordance with the 32 real supercharges?

Not an expert, but from what I've been told the N>8 supergravity theories always contain particles with spin > 2. And these are not well-defined.

 

[tom.stoer]

Is there a list of SUGRA theories (in terms of N and D) from which the following information follows
- particle content
- chiral structure
- able to reproduce the standard model (gauge fields, fermion generations, higgs)
- finiteness (I think there are no rigorous proofs but ongoing research programs)
- low-energy limit of some string theory

 

[tom.stoer]

I simply ask the same questions a second time - hope somebody will read and provide answers - thanks :-)

Is there a list of SUGRA theories (in terms of N and D) from which the following information follows
- particle content
- chiral structure
- able to reproduce the standard model (gauge fields, fermion generations, higgs)
- finiteness (I think there are no rigorous proofs but ongoing research programs)
- low-energy limit of some string theory