This old question is still open. Can I know why it is not Too Broad? There can literally be thousands of different theories and it is ever-growing.
This question has two separate issues, either of which would be sufficient for closure.
- It's too broad. As noted in the question, there are innumerable possible technical explanations for artificial gravity, depending on the work. It's like "How do superheroes fly?" or "How does a sorcerer bind a demon?"
- The way it is worded strongly suggests it is asking for explanations about how a technology could work in "the real world," which are off-topic per our policy on science questions.
As such, this question should be closed.
Keep in mind that this question was asked in 2011, in the earlier days of this site. Back then, we didn't have the same criteria for closing questions as we do now, or as solid community standards. There are many old questions still open that would be closed if they were asked today.