I have written a paper about “multiverse-wide cooperation via correlated decision-making” and would like to find a few more people who’d be interested in giving a last round of comments before publication. The basic idea of the paper is described in a talk you can find here. The paper elaborates on many of the ideas and contains a lot of additional material. While the talk assumes a lot of prior knowledge, the paper is meant to be a bit more accessible. So, don’t be disheartened if you find the talk hard to follow — one goal of getting feedback is to find out which parts of the paper could be made more easy to understand.
If you’re interested, please comment or send me a PM. If you do, I will send you a link to a Google Doc with the paper once I'm done with editing, i.e. in about one week. (I’m afraid you’ll need a Google Account to read and comment.) I plan to start typesetting the paper in LaTeX in about a month, so you’ll have three weeks to comment. Since the paper is long, it’s totally fine if you don’t read the whole thing or just browse around a bit.
Yep, this is roughly the type of cooperation I have in mind. Some minor points:
Overall, I am not sure whether gains from trade would arise in this specific scenario. Perhaps, it’s not better for the civilizations than if each civilization only builds habitats for itself?
As I argue in section “No reciprocity needed: whom to treat beneficially”, the benefit doesn’t necessarily come from the species that we benefit. Even if agent X is certain that agent Y cannot benefit X, agent X may still help Y to make it more likely that X receives help from other agents who are in a structurally similar situation w.r.t. Y and think about it in a way similar to X.
Also, the other civilizations don’t need to be able to check whether we helped them, just like in the prisoner’s dilemma against a copy we don’t have to be able to check whether the other copy actually cooperated. It’s enough to know, prior to making one’s own decision, that the copy reasons similarly about these types of problems.