Re-Thinking the Einstein-Bohr Debate (contd.)

0:00 It's not objective, so there are parts of war, but this is almost contradictory, but it does play an irreducible role, and yet, it's not objective, but it plays an irreducible role because we do science. So classical mechanics is utterly observer-dependent, in my view, of this material. But there is this, sorry to interrupt, just to clarify, your idea is roughly science requires a Boolean algebra, communication and objectivity require a Boolean algebra, and that's perspectival, and so on. And this is something mainstream, here I just cite this mainstream physics, I think that's correct, that was recognized everywhere. But it's not really the details of classical physics, it's Boolean-ness. And I guess I would say we have a non-Boolean science. Yes, for this analysis it's the Boolean-ness. I think this is an extremely important issue. I disagree very strongly with that kind of approach, but I'd like to hear other people. Dennis, would you like to know? And just a moment to ask, why and in what sense does the requirement of the Boolean structure, for example, have a specific type? Because someone has to choose it. There are lots of different Boolean algebers in this non-Boolean, sub-algebers in this non-Boolean, our overall algebra. They have the need of choosing one particular. Yeah, the space is a choice in an electric space. But then you can actually analyze whether or not we have any choice. So it may be the practicals of considerations, force, a specific choice, against the notion of complementarity, by the way, but it may well be like that. And I think the spirit of consistent histories, but please correct me if Simon is wrong, I think that the spirit of consistent histories is precisely that, that we're forced, as IGUS's, information gathering and utilizing systems, to make a very specific choice of boolean, I do think that it depends on which version it consists of history, but there are versions where the beauty of the universe is just an extra special industry, and there, one is forced to rule it. Oh, ok. I endorse the versions that formers, the Gelman Hartel. Yeah, no, me too.

2:30 I think it's Griffiths as the young person, maybe. Or is Alphonse. Or maybe Aisha. Is that right? You mean that every... That for every... Yeah, there's certain democracy and all choices. So there's an account for the one who rebels, because there's no account for the one. I think Chris didn't even have consistency as a condition for sure. Well, no one has consistency. It's all proximate. But that's the difference. I have a question about Berg's historical clarification. One in Boer's reply to the ERP, you said that there was a lot of time about the essential ambiguity. Is Born on Record as clarifying what he meant, that it's essential ambiguity, being an ambiguity between the measurement device and... Yeah, well I'm not sure he's on record, I think it's obvious, but other people find other things obvious from that paper which contradicts what I find obvious. Is this controversial, this essential ambiguity he points out in EPR is that they don't fix the experimental context? I thought that was clear from everything he writes, but I'd be happy to learn that even that is a confused and muddled statement. It's the only part I understood of this reply. I thought I understood of this reply. The notion of ambiguity and the removal of ambiguity is a thing that Manstead was writing right from the very beginning, and it's a result of his deep initial struggle with the very notion of the light quantum, the way Particle Joule is in the radiation field, because you know he was one of the major critics of the light quantum. How can you talk about a wave and a particle at the same time? These terms must be some deep sense ambiguous. So much of Complementary, I think, really grew out of, I don't know whether you would agree with that, but so much of his notions of Complementary grew out of his struggles in the old quantum. Yes, yeah, yeah. Formalism in the new quantum, there is very little to do with it. You are German, aren't you? So you'll be able to translate the book for your colleagues. He also wrote a very nice book by Frey, by the way.

5:00 Yeah, but I think in early war, but maybe throughout, in fact, unambiguous means the same as objective. That's the point made by Miss Chevalet, Catherine, who she's called. Unambiguous means objective. I understood many things that Boris said by this translation. I mean, I was slightly reluctant to ask this earlier, but it does relate to the comments that have just been made. Can we go back to the mathematical slide and the issue of whether we can... I mean, this is going right back to Simon's question, I think it's going right back to Simon's initial question. I mean, what I haven't understood is why what you've said Bohr is committed to in terms of objectivity signs him up to saying that the state of A is going to be a pure state. Yeah, the presentation is simpler, because if you omit purity of omega, then this is only a one-sided justification. The whole argument goes through for arbitrary states, but not in literally the same way. is still valid for arbitrary states, but this presentation is clearer if you restrict yourself to pure states. And I think both Einstein and Bohr would have agreed that settling the states, the pure state, is sufficient. Because, I mean... What exactly is the... Well, I mean, what I was... What I thought was an issue is our ability to talk of the System B in objective terms. And to do that, we need to talk in, you know, our description of the means by which we measure at B have to be classical. But if we're going to, you know, measure one thing about it, we're going to be using one type of measurement apparatus, i.e. one type, you know, one system A. And in choosing that A, we're, you know, deciding to measure, you know, some subset of possible observables at B

7:30 and precluding measurements of other ones, and then, you know... That's right, exactly, yeah. And that would, I think, be a valid version of complementarity, if one that understands, obviously. The choice you have in the abelian sub-algebra of the quantum system A that forms out the apparatus, that could be called complementarity. There are many ways of picking a commutative sub-algebra for non-commutative one, more than two, against war, I'd say, but if you phrase complementarity, it might even be endorsed by the war again. It's just the ambiguity in the choice of a commutative sub-algebra on a given non-commutative one that describes the apparatus, which could be called complementary. The Paul Neumann was the first to make this point, that why are there only two complementary descriptions? Yeah, I can easily buy three and I can easily buy three. Does that answer your question to some extent? And that probably might bring us to an end, just before I thank the speaker, I just mentioned those of you who would like to have dinner with the speaker and some of us, please let me know just after the talk. We have to be seated and have our orders in by 7 o'clock if we want cheap rates. I'd like to thank Jeremy and also Keith Hanewas for all the work they did behind the scenes to bring Klaus to and to look after him while he's been here in Oxford. It wasn't so difficult to bring me here. I'd be happy to accept any invitation to Oxford at any time in Klaus or future. Certainly better than mine. The trouble is, at least in relation to this series of seminars, yours is going to be a very hard act to follow. Thank you very much. Well, thanks for listening. and we'll do it all off the bin. We'll have you and I will go back there.