Is it true than general relativity can be deduced from a maximum mass density for matter?
What makes you think it can be? Did you read about this somewhere?
I can imagine it was a crackpot's fault. It makes a nice crackpot argument to say Einstein used maximum principles in getting special and general theories of relativity.
Threads like this one are the reason we have a rule about citing sources.
I'm closing this thread now, and will reopen it if the original poster asks me by PM to reopen it so that the source can be posted. Without that information, there's not much to say that Shyan didn't already say in #2 of the thread.
Separate names with a comma.