Re: Superposed observers (was No new Einstein)
- From: Charles Francis <charles@xxxxxxxxxxxxxxxx>
- Date: Sun, 28 Aug 2005 07:32:21 +0000 (UTC)
In message <denbh8$2ab6$1@xxxxxxxxxxxxxxxxxxxx>, rof@xxxxxxxxxxxx writes
>Charles Francis <charles@xxxxxxxxxxxxxxxx> writes:
>
>>In message <1124861486.644970.9850@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
>>I.Vecchi <vecchi@xxxxxxxxxxxxx> writes
>>>
>>>RQM brings to the forefront the issue of information exchange among
>>>observers, which is barely mentioned in other approaches. Hence it
>>>provided me with an effective (although incomplete) framework to tackle
>>>conceptual questions such as the intersubjective rather than objective
>>>nature of reality.
>>>RQM has inspired others too (see e.g. [1] or/and ask Charles Francis).
>
>Italo and Charles, I guess you can both provide answers to my
>questions. As I understand it, quantum mechanics can be considered
>as a general procedure for predicting future measurement
>results based on past ones (and on the statistics that we have
>empirically gathered about exactly that relationship between
>past and future results, encoded in such things as the
>Hamiltonian and so on). As such, I understand that the formalism
>of quantum mechanics (with its Hilbert spaces and so on) makes
>no reference to any physical object, except if one considers
>a measurement result to be a physical object.
Yes
>
>Now the relational interpretation, unless I'm mistaken,
>attempts (like most interpretations of quantum mechanics),
>to say that quantum mechanics is not a technique for
>predicting the results of measurements, but is rather
>a theory which asserts something about what exists
>ontologically, namely interacting systems with various
>relationships between them.
Yes
>It is presented as though
>it were a great step forward in our understanding
>of the world,
I don't actually think so. Or at least the insight was clearly expressed
by Descartes, long before quantum theory. Since then I think we have
been a bit short of insights, but people have been chipping away slowly.
I see RQM, as part of this chipping away process.
> but unless I'm mistaken, the great
>insight is supposed to occur when somebody abandons
>a different ontology (say, for example, the idea
>of absolute space, or the idea that certain things
>aren't observer-dependent, but exist absolutely)
>and adopts this relational ontology instead.
Yes. That is what Descartes, Liebniz advocated, coming down from
Leucippus, whose original insight was to avoid Zeno's paradoxes.
>
>>The fundamental idea that measurement is a relationship between matter
>>and matter makes it natural that when no measurement is possible, nor is
>>there a well defined value for the measured quantity. An observer in the
>>box sees the cat alive or dead. An observer outside the box has no
>>information, and is essentially just describing the probability of
>>whether the cat is alive or dead. I see no deeper problem here than
>>there is with classical probability theory. Two observers with different
>>information correctly ascribe different probabilities to the same event.
>
>Relationalism seems to advocate that we say that, when Nick
>looks at the cat, then the cat becomes alive or dead "relative to"
>Nick, but is not yet alive or dead relative to (for example) me.
>When I look at the cat (or ask Nick), then the cat will become
>alive or dead relative to me.
No. The cat is alive or dead. But until you ask Nick you can only give a
probability.
>
>But the obvious question is: If the cat is dead relative to
>Nick, can it be alive relative to me?
No. It can't.
>
>If not, then that means that, if the cat is dead relative to Nick,
>then the cat is just dead (relative to everybody, that is, absolutely).
>In that case, the expression "The cat is dead relative to Nick"
>really just means "The cat is dead," and the "relative to Nick"
>bit, which relationalism insists should be added to the end of the
>sentence (in order to remove so-called conceptual problems),
>is useless, except in so far as it might indicate that Nick
>is aware that the cat is dead.
I think the trouble is you are looking at the wrong problem. The cat is
alive or dead, no issue, no relative clause needed. The issue starts
when you ask the position of a particle.
>
>The same question can be asked of the energy of a two-state
>system. Can it have one well-defined energy relative to
>me and a different well-defined energy relative to
>somebody else? If no, it's not relational,
As I say, wrong scenario.
>>The problem moves on, and becomes one of explaining why there is a wave
>>equation. As far as I can see the main reason that hasn't been solved is
>>that people who study foundations fight shy of making it relativistic,
>>whereas people who study relativistic field theories have no time or
>>sympathy for foundations.
>
>They have no understanding of foundations either.
I was trying to be too polite to say so. They get very upset if you tell
them such things.
>
>>Plus of course, there are some really nasty
>>mathematical problems which make them think qft can't be built on qm.
>
>Do you mean Haag's theorem? Or do you mean the problems with
>making path integrals rigorous? Or finding an actual example
>of an interacting field theory? Or something to do with
>renormalization?
All of those. But the worst is the Landau Pole, I think.
Regards
--
Charles Francis
.
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