vanesch said:What I meant was the following. SA and you seem not to agree with me, but I think that the RQM formulation is entirely "observer" centered, and is about information an observer has, to himself, which is not available to eventual other observers.
Now, the (strong) holographic principle, as I understand it, comes down to saying that whatever we can know about anything, is entirely determined by the closed surface around us ; or even (strong version), that that is in fact the only thing that really is, and the "volume behind it" is just an illusion created by the information flowing in from the surface ; with suitable reformulation, all physics is the physics of the surface around us, observers.
Now, consider each "observer" in its own "plastic bag", thinking there's an entire universe behind it, with other observers walking around in it and all that, but he looks just at the physics of his plastic bag ; nevertheless, he'll see his "peer observers" on his plastic bag agree with him.
And so each observer lives in his own plastic bag, with his own "knowledge" and information flow coming off it, thinking there's an entire universe behind it.
This is then nothing but the "subjective worlds" I talked about - though now they become indeed "individually objective" (but surely with some form of solipsism to it).
Well is relativity solipsism? It seems to meet your definition; there is no absolute energy, length or time seen by everybody, rather energy, length and time are "oberver dependent". Each observer in his own rest frame sees a length, energy, and time that is "ordinary" for him, but no other observer who has a velocity relative to the first one will see those values. And this is not just illusion; as we well know from experiment, the different definitions in two "interacting" frames have real consequences for the observers in them.
So according to your definition hasn't physics been solipsist since 1905?