Various things that I’ve been wanting to mention:<\/p>\n
Steven Hawking has a paper<\/a> out, on his version of the Landscape story, using amplitudes that don’t rely upon string theory or eternal inflation. But just like the string theory Landscape I don’t see how his proposal is testable. It completely gives up on saying anything about particle physics, even statistically<\/p>\n \nIf the volume weighted amplitude for the standard model vacuum is non-zero, it is irrelevant what the volume weighted amplitudes for other vacuum states are. The theory can not predict a unique vacuum state. Instead we have to input that we live in the standard model vacuum.\n<\/p><\/blockquote>\n He ends with<\/p>\n \nThe amplitudes will be highest for states in which the whole universe is in a single state, rather than a mosaic of different states, as predicted by eternal inflation. There will be no primordial production of topological defects, such as monopoles, and cosmic strings. Not all states in the landscape will have significant amplitudes, but there will be more than one that do, so M theory does not predict a unique low energy particle physics theory. It is implausible that life is possible only in one of these states, so we might have chosen a better location.\n<\/p><\/blockquote>\n John Baez has a new This Week’s Finds<\/a> out, with interesting discussions of the topos-theoretic approach to quantum theory, and the analogy between the integers and three-dimensional space. This semester he is running a seminar<\/a> on “Geometric Representation Theory” (not clear how close this is to the use of the term by those representation theorists who work with D-modules). Videos and lecture notes from the talks are available, along with some blog postings (see here<\/a> and here<\/a>).<\/p>\n As always, Terry Tao’s blog has wonderful postings and articles, often of a general expository nature. For some recent examples, see one about the Schrodinger Equation<\/a>, and another about Jordan normal form<\/a>.<\/p>\n Besides excellent expository physics postings such as the recent one on single top production<\/a>, Tommaso Dorigo gives a more realistic view of the academic life than most other blogs. For some understanding of how academics feel about the travel opportunities that conferences present, and what they think about the question of whether their employer should be financing what sometimes feels like a vacation, see his recent posting on Ethical aspects of professional conference-going<\/a>. I strongly endorse his recommendation of the David Lodge novel Small World<\/em>.<\/p>\n There’s a string theory wiki out there, aimed at students trying to learn string theory, which has been set up by the Centre for Research in String Theory<\/a> at Queen Mary College. Much of the site is a listing of the one thousand or so review and other papers an aspiring young theorist should read and absorb to get an idea of what is going on with string theory. Also listed are various blogs, including this one, that might save students some of this reading…<\/p>\n","protected":false},"excerpt":{"rendered":" Various things that I’ve been wanting to mention: Steven Hawking has a paper out, on his version of the Landscape story, using amplitudes that don’t rely upon string theory or eternal inflation. But just like the string theory Landscape I … Continue reading