On Thursday, September 12, 2024 at 11:08:32 PM UTC-6 Bruce Kellett wrote:
On Fri, Sep 13, 2024 at 1:07 PM Liz R <[email protected]> wrote: On Friday 13 September 2024 at 11:47:31 UTC+12 Bruce Kellett wrote: On Fri, Sep 13, 2024 at 9:28 AM Liz R wrote: Yes I wondered about that, but it's possible that physics isn't *intrinsically* random. No, that isn't possible. Randomness is intrinsic, and not derivable from anything else. This is the sort of thing that made me think of "oracles". What sort of physical (or mathematical) process could, at least in principle, be intrinsically random? You might want to call intrinsic randomness an "oracle", but I don't really know what that means. Intrinsic randomness in physics would have to be a primitive, independent of other deterministic laws. The sort of thing that I have in mind is spontaneous collapse of the wave function, or the random 'flashes' of GRW theory. (Rather than apparently random due to ignorance of an underlying lower-level deterministic mechanism.) An oracle that delivers the next digit in Chaitin's constant, as mentioned by Russell, might be the sort of thing - which could mean a suitable source of randomness in physics is the "universal dovetailer" or something similar. I don't see how the universal dovetaier could be a source of intrinsic randomness. It is strictly deterministic, and if you have branches as in many-worlds, choosing between the branches can be implemented only by some other intrinsically random process -- it can't be internally generated. It could be based on something computable, and only appear random from our perspective - presumbly some versions of many-worlds would fit the bill. No, many-worlds is a decided failure as far as randomness is concerned. You cannot get intrinsic randomness as exhibited by quantum phenomena from a deterministic theory such as many-worlds. I thought you could get the appearance of randomness from a first-person perspective in MW? Has that been shown to not work? I don't think that works. The idea often put forward is something along the lines of self-locating uncertainty -- out of all the branches, which one am I on? But that is only apparent randomness, and to get such an idea to work, you need to be able to make a random choice between branches. Such randomness will be intrinsic in that It doesn't come from anywhere else (it is not already part of the theory). So in order to generate such apparent randomness you actually need an independent source of intrinsic randomness (to be able to make your self-locating choice.) Also, although various attempts to show hidden variables have fallen down, it's always possible something of that sort might be involved that we haven't thought of yet. That is just a cheap let-out: "It could be something we haven't thought of yet. There are very good reason to think that intrinsic randomness cannot arise from a deterministic theory. You can get randomness from ignorance, as in classic statistical mechanics, but that is not intrinsic -- things are still deterministic if you have complete knowledge. Which is not the case in QM. Well, yes - by definition, intrinsic randomness can't arise from a deterministic theory. However, I will wait for your ideas on the types of physical or mathematical processes that could lead to intrinsic randomness before commenting on this further, as I can't get past that first hurdle yet! Yes, by definition, intrinsic randomness cannot arise from a deterministic theory, so there are no physical processes of the common type known to date that can lead to it. One needs a separate source of intrinsic randomness. That is one of the strengths of GRW collapse theory: it is perhaps the only theory around at the moment that has an explanation of intrinsic randomness, since randomness is a primitive in that theory. Other hidden variable theories, such as Bohmian Mechanics, can explain quantum randomness, but only as a consequence of ignorance about the influence of every other particle in the universe. That is still deterministic (though non-local), not intrinsic. Bruce *Isn't Bohmian Mechanics a deterministic theory which reproduces the probability results of QM? AG * -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/d92afe79-c09c-4efc-8322-d069930c87c0n%40googlegroups.com.
