tag:blogger.com,1999:blog-8148573551417578681.post2262550319033100256..comments2020-08-05T09:34:01.581-07:00Comments on Dark Buzz: Jaynes on uncertainty or obscurityRogerhttp://www.blogger.com/profile/03474078324293158376noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-8148573551417578681.post-62049206286258560052015-05-12T00:13:07.425-07:002015-05-12T00:13:07.425-07:00Roger, my comment was not entirely serious and was...Roger, my comment was not entirely serious and was intended to mock the true believers of 'Symmetry Principles Forever!!!' who are especially fanatical working in QFT. The reason being symmetry arguments and group theoretical reasoning are strictly speaking unnecessary in non-relativistic quantum theory. Its not really well known today but in the heyday (20's and 30's) of quantum theory, group theory was widely considered a plague of useless abstraction (Gruppenpest in German). I Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-47039234502126090982015-05-11T23:30:59.158-07:002015-05-11T23:30:59.158-07:00>> Just look at the picture of Jaynes, and c...>> Just look at the picture of Jaynes, and compare it to the wild-haired physicists! Who is more likely to give you the straight truth about the nature of reality? <br /><br />Wow, I've seen some probabilistic extrapolations from small data sets before.Jon Burdickhttps://www.blogger.com/profile/02548776058585897717noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-29274791073951159762015-05-11T21:23:08.479-07:002015-05-11T21:23:08.479-07:00When I say quantum mechanics, I mean to include qu...When I say quantum mechanics, I mean to include quantum field theory. Yes, QFT is a local and relativistic theory, and I would not say it has problems, but those who complain about EPR paradoxes and other such matters have the same objections to QFT.Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-64329128704348741782015-05-11T21:20:09.775-07:002015-05-11T21:20:09.775-07:00Well I can't answer that question for everyone...Well I can't answer that question for everyone, but I can give you Jaynes's reason. Jaynes was there at the birth of QFT, knew or studied from most of the key players, and in his day job was a QFT ninja. He also seems to be have been a big fan of Schwinger.<br /><br />The reason he persisted in looking at QM seems to have been that he thought all the major success attributed to QFT didn't actually use QFT and could be derived from conceptually simpler theories that might serve as a better jumping off point to discover new physics. Or could at least suggest interesting experiments which might yield which stood some kind of chance of discovering something useful.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-58661538940388156322015-05-11T20:57:00.210-07:002015-05-11T20:57:00.210-07:00I don't know why people still talk about Quant...I don't know why people still talk about Quantum Mechanics as if Quantum Field Theory does not even exist. The two are very different. All the paradoxes of QM disappear in QFT and its conceptual framework is necessary for building intuition for doing engineering. I think its just too hard for literally everyone. Ever since the days of Schwinger when he was ignored for being too formal (too many equations), its been a descent into anti-science behaviour.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-33702242580682440682015-05-11T14:38:28.652-07:002015-05-11T14:38:28.652-07:00Then we are led to ask what distributions are more...Then we are led to ask what distributions are more real than others. The game is endless when it comes to essentialisms. Feynman basically conceded that "negative probabilities" were just convenient: http://cds.cern.ch/record/154856/files/pre-27827.pdf<br /><br />I see the use of negative probabilities in front-running the options market. Seems that's all "smart" people are good for these day. Financial parasitism by means of central banker ZIRP.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-83382931150090282932015-05-11T10:19:13.939-07:002015-05-11T10:19:13.939-07:00At the end of his life, Jaynes saw his work in pro...At the end of his life, Jaynes saw his work in probability theory as a major proven success, but had nothing like the same confidence about his work in QED. <br /><br />One gets the feeling he strongly felt that Bayesian statistics had a huge unrealized role to play in understanding Quantum Mechanics, but he likely thought his own speculations would have to change a lot before it was all said and done.<br /><br />Still, it's a pleasure to read a first rate physicist thinking critically about Quantum Mechanics in a very down to the earth way, without any of the usual mysticism and without any of the usual "I'm the next quirky lone wolf super genius who's going to revolutionize our understanding of the world" style of self promotion and inflated self regard.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-89914340487453968332015-05-11T10:07:32.345-07:002015-05-11T10:07:32.345-07:00Roger,
You're right about probability, but th...Roger,<br /><br />You're right about probability, but the idea of probabilities as modeling a physical "randomness" in the universe is so strong in most people that it requires some kind of explanation. Why do people keep being drawn to this false conception of probability?<br /><br />Well, there's an interesting story there. The first step is to always carefully distinguish between frequencies and probabilities. They may both be positive and sum to 1, but they are different in nature. Real physical frequencies are no different than any other fact of nature. They can measured, estimated, predicted, and so on. They have a physical reality independent of our state of information. Probabilities on the other hand measure uncertainty implied by a state of information and can change dramatically when our state of information changes.<br /><br />The confusion is severe because we can model the uncertainty of any physical thing, including frequencies. Thus given a frequency distribution f_1,...,f_n we can talk about the probability of it P(f_1,...,f_n). Again note that P() is describing the uncertainty in our knowledge about a real frequency distribution and is not itself the frequency of anything.<br /><br />What often happens in statistics (and statistical mechanics) is that for large n, these probabilities distributions P() become sharply peaked about single distribution F_1,...,F_n. This distribution is really the mode or “mostly likely” value of P(f_1,...,f_n).<br /><br />Because of that, if real observed frequencies distributions f_1,...,f_n lie in the high probability region of P() they will be approximately similar to F_1,...,F_n. It will appear in fact as if the f_1,...,f_n were a “random draw” from F_1,...,F_n.<br /><br />When people conceive of a probability distribution as a modeling a physical randomness, or talk about “estimating a probability” distribution, and so on, they're really talking about F_1,...,F_n. But instead of calling it the “most likely frequency distribution” they very confusingly call it a “probability distribution”. It's amazing how much confusion can be swept away by always calling frequencies “frequencies” and reserving probability for modeling uncertainty.<br /><br />As a side note, finding the mode of P(f_1,...,f_n) involves a maximizing procedure. To cut a long story short, in many instances this maximizing condition is equivalent to finding a F_1,...,F_n which maximizes the “entropy” subject to constraints. That's why you get the bizarre unexplained historical fact that almost all the distributions (normal, binomial, Poisson,....) of regular classical statistics are in fact maximum entropy distributions (bizarre because classical statistics had nothing to do with statistical mechanics historically).<br /><br />Incidentally, one consequence of this perhaps relevant to Quantum Mechanics, is that all probability distributions satisfy the same formulas (sum and product rule). However, the F_1,...,F_n can potentially follow any rule or transform in any way, just like any physical value potentially can. So whenever you have something that looks like a "probability distribution" but doesn't follow the usual rule of probability theory, then maybe you're actually talking about a F_1,...,F_n. Anonymousnoreply@blogger.com