A question for TDT gurus. Do acausal trade, and other acausal coordinations, require a complete instance of each cooperating agent at each of the acausally connected sites? It seems that there at least has to be a model of each agent at each site, if not a "complete instance".
For example, the TDT solution to Newcomb's problem, as I understand it, amounts to you coordinating with the copy of you or the model of you which exists in Omega. There's only one actively coordinating agent, you (Omega is only reactive to whatever you decide), and there's a copy or a model of you at both ends of the arrangement.
Similarly, when people imagine AIs coordinating acausally - let's say, two AIs in two different Tegmark-level-IV worlds - we can say that at the very least, each AI that is a party to the deal must have a concept of the other one's existence, or else the deal could never get started. (If we imagine equilibria reached by whole populations of AIs scattered throughout a multiverse, then the local model may be of a subpopulation of AIs sharing a characteristic, rather than of individual AIs.) So it's not just a matter of "I'm here and you're there". There has to be a model of you here, and there has to be a model of me there. But how detailed do the models have to be?
To focus on Newcomb's problem: TDT still one-boxes even if Omega is a little bit bad at predicting whether or not you will one-box. How bad Omega can be while still resulting in TDT one-boxing depends on the precise rewards for one- and two-boxing.
Shminux asked a similar question a while ago and I forgot to tell him that it's in the TDT paper. Hey, shminux: it's in the TDT paper.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.