tag:blogger.com,1999:blog-5439168179960787195.post7196843522666194257..comments2024-03-28T17:13:01.117+10:00Comments on Condensed concepts: To commute or not to commuteRoss H. McKenziehttp://www.blogger.com/profile/09950455939572097456noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5439168179960787195.post-51452607472583450502010-03-12T07:28:43.127+10:002010-03-12T07:28:43.127+10:00Oh, and BTW, I _HIGHLY_ recommend Lipkin's &qu...Oh, and BTW, I _HIGHLY_ recommend Lipkin's "Quantum Mechanics: New Approaches to Selected Topics" for a lucid and very nicely pedagogical discussion of second quantization. The book is excellent generally, and reads more like a novel than a textbook (even though it's all physics). Curl up in bed with one! Its a Dover edition, too, so its something less than $600/copy.Seth Olsenhttps://www.blogger.com/profile/09304457461800104790noreply@blogger.comtag:blogger.com,1999:blog-5439168179960787195.post-65602939452068874092010-03-12T07:25:12.324+10:002010-03-12T07:25:12.324+10:00I missed the group again. Probably this will keep...I missed the group again. Probably this will keep up for a while until things settle down.<br /><br />I was not terribly impressed that Phillips did not go further into how you take an expectation value of a second quantized expression, nor did he put in any discussion of the difference between different relevant vacua. <br /><br />It has not impressed me at _all_ that most texts on many-body theory do not do this justice. I certainly think it is _extremely_ important. What good is knowing how to write an operator if you can't take its expectation? Understanding the identities that hold for the expectation (or higher moments) is critical for understanding how statistical models can be created. <br /><br />This is OBVIOUSLY important - for example, didn't Hubbard simulate his model instead of solving it, by making the one-body potential a random variable? How can anyone understand the cleverness of this idea unless they understand how to manipulate expectation values.<br /><br />It's possible that he mentioned it and I missed it, but for this to be true he must not have given it much discussion. <br /><br />I was even LESS impressed when I saw that one of the exercises in the back asks the reader to actually take an expectation. <br /><br />Very bad form, if you ask me.Seth Olsenhttps://www.blogger.com/profile/09304457461800104790noreply@blogger.com