No, it can be located absolutely anywhere. However you're right that the light cones with vertex close to Big Bang will probably have large weight to low K-complexity.
Ah, I see what you're getting at. If the vertex is at the Big Bang, then the shortest programs basically simulate a history of the observable universe. Just start from a description of the laws of physics and some (low entropy) initial conditions, then read in random bits whenever there is an increase in entropy. (For technical reasons the programs will also need to simulate a slightly larger region just outside the light cone, to predict what will cross into it).
If the vertex lies elsewhere, the shortest programs will likely still simulate starting from the Big Bang, then "truncate" i.e. shift the vertex to a new point (s, t) and throw away anything outside the reduced light cone. So I suspect that this approach gives a weighting rather like 2^-K(s,t) for light-cones which are offset from the Big Bang. Probably most of the weight comes from programs which shift in t but not much in s.
The temporal discount here can be fast e.g. exponential.
That's what I thought you meant originally: this would ensures that the utility in any given light-cone is bounded, and hence that the expected utility converges.
...given that a super-strong future filter looks very unlikely, most of the probability will be concentrated on models where there are only a few civilisations to start with.
This looks correct, but it is different from your initial argument. In particular there's no reason to believe MWI is wrong or anything like that.
I disagree. If models like MWI and/or eternal inflation are taken seriously, then they imply the existence of a huge number of civilisations (spread across multiple branches or multiple inflating regions), and a huge number of expanded civilisations (unless the chance of expansion is exactly zero). Observers should then predict that they will be in one of the expanded civilisations. (Or in UDT terms, they should take bets that they are in such a civilisation). Since our observations are not like that, this forces us into simulation conclusions (most people making our observations are in sims, so that's how we should bet). The problem is still that there is a poor fit to observations: yes we could be in a sim, and it could look like this, but on the other hand it could look like more or less anything.
Incidentally, there are versions of inflation and many worlds which don't run into that problem. You can always take a "local" view of inflation (see for instance these papers), and a "modal" interpretation of many worlds (see here). Combined, these views imply that all that actually exists is within one branch of a wave function constructed over one observable universe. These "cut-down" interpretations make either the same physical predictions as the "expansive" interpretations, or better predictions, so I can't see any real reason to believe in the expansive versions.
So I suspect that this approach gives a weighting rather like 2^-K(s,t) for light-cones which are offset from the Big Bang.
In some sense it does, but we must be wary of technicalities. In initial singularity models I'm not sure it makes sense to speak of "light cone with vertex in singularity" and it certainly doesn't make sense to speak of a privileged point in space. In eternal inflation models there is no singularity so it might make space to speak of the "Big Bang" point in space-time, however it is slightly "fuzzy".
...I
The 'Irrationality Game' posts in discussion came before my time here, but I had a very good time reading the bits written in the comments section. I also had a number of thoughts I would've liked to post and get feedback on, but I knew that being buried in such old threads not much would come of it. So I asked around and feedback from people has suggested that they would be open to a reboot!
I hereby again quote the original rules:
I would suggest placing *related* propositions in the same comment, but wildly different ones might deserve separate comments for keeping threads separate.
Make sure you put "Irrationality Game" as the first two words of a post containing a proposition to be voted upon in the game's format.
Here we go!
EDIT: It was pointed out in the meta-thread below that this could be done with polls rather than karma so as to discourage playing-to-win and getting around the hiding of downvoted comments. If anyone resurrects this game in the future, please do so under that system If you wish to test a poll format in this thread feel free to do so, but continue voting as normal for those that are not in poll format.