Is M-Theory and 11D Supergravity the same thing? Reading Hawking, he uses 11D Supergravity and M-Theory interchangeably.
http://www.hawking.org.uk/quantum-cosmology-m-theory-and-the-anthropic-principle.html
There are various statements such as:
"11D Supergravity is the low energy limit of M-theory."
"M-theory is the [or one of the] UV completion[s] of 11D Supergravity".
"p-branes are solutions of 11D Supergravity."
So if Supergravity is the low energy limit of a theory of membranes but ALSO membranes are solutions of supergravity... how is that possible?
Also, what does it mean for p-branes to be solutions of supergravity? Is it like black holes are solutions? And p-branes are like n-dimensional black holes?
Any help clearing this up?