| > You seemingly consider one measurement and expect to see Born rule Huh??? No, of course not. The Born rule is about probabilities. It cannot manifest in a single measurement. > classical behavior emerges by tracing, mathematically, not as a physical process? No. The mathematical description of classical outcomes emerges by tracing, which is to say, by discarding information. The physical interpretation of that is left open. > In MWI classical behavior emerges as a physical process That's right. MWI commits to a physical interpretation of the math. But there is no scientific or philosophical justification for this, and in fact, when you dig into the details all kinds of problems emerge that are swept under the rug by its proponents. Nonetheless, many MWI proponents insist that it is the One True Interpretation, including some who really ought to know better. > each observer naturally observes their branch from inside, and it looks isolated from other branches. Yes, I know. But this doesn't solve the problem. In order to get a mathematical description of me I have to trace the wave function in my preferred basis, which is to say, I have to throw out all of the other branches. And this is not just a computational hack. It's mathematically necessary. Discarding information is the only way to get classical, irreversible processes (like measurement) out of the unitary dynamics of the wave function. So a reasonable interpretation of the math is that I exist only if parallel universes don't. And I'm pretty sure I exist. I'm not telling you this because I expect you to accept it, merely to show you that the MWI is not self-evidently the One True Interpretation. |