[T]here are many classical worlds equally real to the single world we experience. Surely you accept this.
Surely? I don't even know what it means. Words "real" and "experience" are close neighbours in my vocabulary, real unexperienced world sounds a lot like an oxymoron, at least if not based on a really strong argument.
What gets worse when you move to QFT?
Nothing. I have tried to (incompletely of course) explain the relation between the conventional and relativistic Hamiltonian formalism in case of mechanics, where it is slightly more intuitive and simpler. If you address my first remark, you have disinterpreted it. I don't say that move to QFT isn't justified, but that one conventional argument used to support this move isn't good.
The classical states are not ontologically fundamental in ordinary QM. If that's what you mean by MWI...
It isn't. By MWI I mean probably the same thing as anybody else. Nothing particularly related to classical states. I have discussed classical states in order to give some background to my intuitions. My statement was that probably the quantum states are a redundant concept.
I'm happy to talk about QFT as a bunch of ordinary QM systems, one for each reference frame.
I would understand that QFT is a bunch of QM systems, one for each spacetime point. I don't understand what reference frames do with it. In any fixed reference frame QFT has infinite number of degrees of freedom. Maybe you speak about momentum representation? I am confused.
Please read the post before voting on the comments, as this is a game where voting works differently.
Warning: the comments section of this post will look odd. The most reasonable comments will have lots of negative karma. Do not be alarmed, it's all part of the plan. In order to participate in this game you should disable any viewing threshold for negatively voted comments.
Here's an irrationalist game meant to quickly collect a pool of controversial ideas for people to debate and assess. It kinda relies on people being honest and not being nitpickers, but it might be fun.
Write a comment reply to this post describing a belief you think has a reasonable chance of being true relative to the the beliefs of other Less Wrong folk. Jot down a proposition and a rough probability estimate or qualitative description, like 'fairly confident'.
Example (not my true belief): "The U.S. government was directly responsible for financing the September 11th terrorist attacks. Very confident. (~95%)."
If you post a belief, you have to vote on the beliefs of all other comments. Voting works like this: if you basically agree with the comment, vote the comment down. If you basically disagree with the comment, vote the comment up. What 'basically' means here is intuitive; instead of using a precise mathy scoring system, just make a guess. In my view, if their stated probability is 99.9% and your degree of belief is 90%, that merits an upvote: it's a pretty big difference of opinion. If they're at 99.9% and you're at 99.5%, it could go either way. If you're genuinely unsure whether or not you basically agree with them, you can pass on voting (but try not to). Vote up if you think they are either overconfident or underconfident in their belief: any disagreement is valid disagreement.
That's the spirit of the game, but some more qualifications and rules follow.
If the proposition in a comment isn't incredibly precise, use your best interpretation. If you really have to pick nits for whatever reason, say so in a comment reply.
The more upvotes you get, the more irrational Less Wrong perceives your belief to be. Which means that if you have a large amount of Less Wrong karma and can still get lots of upvotes on your crazy beliefs then you will get lots of smart people to take your weird ideas a little more seriously.
Some poor soul is going to come along and post "I believe in God". Don't pick nits and say "Well in a a Tegmark multiverse there is definitely a universe exactly like ours where some sort of god rules over us..." and downvote it. That's cheating. You better upvote the guy. For just this post, get over your desire to upvote rationality. For this game, we reward perceived irrationality.
Try to be precise in your propositions. Saying "I believe in God. 99% sure." isn't informative because we don't quite know which God you're talking about. A deist god? The Christian God? Jewish?
Y'all know this already, but just a reminder: preferences ain't beliefs. Downvote preferences disguised as beliefs. Beliefs that include the word "should" are are almost always imprecise: avoid them.
Additional rules: