Weak energy condition[1]. In general the energy conditions are useful for analysis of the Einstein equations, but general relativity does not demand them. So vi

Weak energy condition[1]. In general the energy conditions are useful for analysis of the Einstein equations, but general relativity does not demand them. So violating the energy conditions is somewhat theoretically sound, but one can only say so much about general relativity with violated energy conditions. ( For example a lot of stuff we know about black holes only holds, if some energy conditions are satisfied.) [1] https://en.wikipedia.org/wiki/Energy_condition https://en.wikipedia.org/wiki/Energy_condition