String Theory
drorzel | November 19, 2008A little while back, when I complained about the treatment of the multiverse in Anathem, a number of people commented to say that it wasn't all that bad. And, indeed, they were right. Compared to last night's History Channel program on "Parallel Universes," Stephenson's book is a miracle of subtle nuance, teasing out the crucial distinctions between different theories, and making them clear to the reader.
Yeesh. That was so actively irritating that I don't know where to start. So I won't-- you can read what I wrote in the earlier post, and apply it to the History Channel, ten times over.…
drorzel | July 30, 2008Over at Backreaction, Bee has a nice post about uncertainty, in the technical sense, not the quantum sense. The context is news stories about science, which typically do a terrible job of handling the uncertainties and caveats that are an essential part of science.
Properly dealing with uncertainty is one of the hardest parts of science. Which is why I'm particularly impressed by people who spend their whole careers measuring nothing but uncertainties-- looking for an electric dipole moment for the electron, or parity non-conservation, or Lorentz violation, or any of a bunch of other things…
drorzel | March 29, 2008Over at Evolving Thoughts, John Wilkins pokes string theorists:
Ernst Rutherford, the "father" of nuclear physics, once airily declared "In science there is only physics. All the rest is stamp collecting". By this he meant that the theory of physics is the only significant thing in science. Such mundane activities as taxonomy in biology were just sampling contingent examples of physics.
So it is with some amusement that I note that in order to make sense of string theory, a group of physicists have been trying to do taxonomy over string theories.
I'm never sure who reads what blogs, but I…
drorzel | December 5, 2007There's a piece by Michael Dine in Physics Today this month with the ambitious title "String theory in the era of the Large Hadron Collider, thus combining two of my very favorite topics... I was going to give it a pass, but I was surprised to discover that it's freely available-- most of their articles are behind a subscription wall-- and as long as it's linkable, I might as well say something about it.
The bulk of it is stuff that anybody with a passing familiarity with high-energy physics has heard before. Unification of forces, blah, blah, quantum gravity, blah, blah, only game in town.…
drorzel | November 26, 2007The infamous Davies op-ed has been collected together with some responses at edge.org, and one of the responses is by Sean Carroll, who reproduces his response at Cosmic Variance. Sean's a smart guy, and I basically agree with his argument, but I'm a contrary sort, and want to nitpick one thing about his response.
He builds his response around the question, raised by Davies, "Why do the laws of physics take the form they do?" He considers and discards a few responses, before writing:
The final possibility, which seems to be the right one, is: that's just how things are. There is a chain of…
bergman | August 26, 2007The title of this post is a famous question (posed, for example, by Joe Polchinski) which is modeled after an even more famous question by Ken Wilson, "What is Quantum Field Theory?". I certainly can't answer the first question, but Wilson's question now does have a widely agreed upon answer (which is sadly not well presented in a popular literature that continues to repeat old myths about regularization) which I will mention a bit later
What I would mainly like to do, however, is to answer the much easier question, "What is string perturbation theory?" But before getting to that, let's talk…
bergman | August 20, 2007Thanx to everyone for all the interesting questions in the previous thread. I apologize for not being able to answer every one of them. I just arrived at a workshop on Long Island, and I'm also feeling a bit under the weather. From what I've seen so far, I think I will do a post on what is perturbative string theory and what does it have to do with spacetime and gravity (maybe it will even lead into a post on what is background independence). Feel free to use this thread for more questions if you like.
lundblad | August 18, 2007I see below that (in what comes as a total surprise) the string thread has already gotten lively. As an experimentalist doing quantum mechanics at the ultra-low-energy end, I don't have a strong opinion on string theory qua theory, and I really don't have a strong opinion on the sociology-of-theory business, beyond saying that I'm not a cynic, and that I find articles in the popular press about Str1ng Warzz a bit tacky.
I'm also not really qualified to weigh in: my only particle theory background was a year of QFT from a phenomenologist out of Peskin & Schroeder, and while I came…
bergman | August 17, 2007First of all, I'd like to thank Chad for the keys to his internet-house for the next few weeks. If you're here, you know that one of the things Chad believes in (and is quite good at) is using his weblog for the exposition of science for the general public. While I don't think I can manage any funny dog stories, I'd like to try to follow his example. I have some ideas already planned (such as, god help me, a three part series on the multiverse), but I thought as an initial post here, I'd go straight to the public. What do you want to hear about? Is there some aspect of string theory, quantum…
drorzel | June 25, 2007There's a lot of buzz in physics blogdom about the Strings 07 meeting, which starts today in Spain. They currently have a list of speakers, and promise slides and video to come.
Also, there's a new paper by Edward Witten on the arxiv, cue sound of heavenly choirs:
We consider the problem of identifying the CFT's that may be dual to pure gravity in three dimensions with negative cosmological constant. The c-theorem indicates that three-dimensional pure gravity is consistent only at certain values of the coupling constant, and the relation to Chern-Simons gauge theory hints that these may be…
drorzel | April 3, 2007It's summed up nicely by the discussion at Cosmic Variance, and spelled out explicitly in comment #125 by Marty Tysanner:
Sean coaxingly requested,
Come on, string theorists! Make some effort to explain to everyone why this set of lofty speculations is as promising as you know it to be. It won't hurt too much, really.
It seems remarkable to me, 120+ comments later, how few people have responded in this vein. Over at Clifford's blog there have been some angry discussions (e.g., this and this) about the merits of Lee's and Peter's books, and some string theorists and partisans were quite vocal…
drorzel | April 1, 2007As we look at science in general, and physics in particular, a clear pattern emerges: the scientific endeavours most worthy of praise and acclaim are the most abstract and mathematical sciences. Physics is of greater worth than biology, theoretical physics is more worthy than experimental physics, and high-energy particle theory is the most fundamental and important field in the history of human though. Rather than deriding string theory as an excessively mathematical dead end, as many anti-science America-hating Bush-bashing politically correct feminist shrub-hugging liberal communist dupes…
drorzel | February 23, 2007It's a good day for people posting about science I don't understand...
Peter Woit points to the Non-Commutative Geometry blog, at which Alain Connes, the godfather of non-commutative geometry, is posting. It's not the most polished blog, but if you can understand what they're talking about, it's probably interesting.
Scott Aaronson is excited about new results in quantum computing, where somebody has "announced a quantum algorithm for evaluating NAND trees in O(âN) time." I'm not quite sure what he's talking about either, but it has something to do with ants, sugar cubes, and teaching…
drorzel | January 31, 2007Discover magazine has announced a contest:
Your goal is to create a video that quickly and clearly explains perhaps the most baffling idea in the history of the world: string theory.
And the best part is that you have just two minutes.
You'll be happy to know that Peter Woit has already bowed out (suggested concept: standing in front of a whiteboard, hopping up and down, and yelling, "It's crap! Crap crap crap crap crap!" for two minutes).
This is a sure path to fame and fort-- well, actually, they don't appear to be offering money, so just fame. Well, actually, they just promise to feature…
drorzel | January 13, 2007One of my favorite experiments in physics has released a new set of results in Physical Review Letters, putting experimental limits on the size of any extra dimensions of the sort predicted by string theory:
We conducted three torsion-balance experiments to test the gravitational inverse-square law at separations between 9.53 mm and 55 µm, probing distances less than the dark-energy length scale λ~85 µm. We find with 95% confidence that the inverse-square law holds (|α|<=1) down to a length scale λ=56 µm and that an extra dimension must have a size R<=44 µm.
You'll need a…
drorzel | December 22, 2006Scott Aaronson is offering his services to the highest bidder in the String Wars. His prices may be a little steep-- a well organized review article will set you back $2 million, though a sloppy and poorly sourced one is probably cheaper-- but really, isn't it worth it to have the second funniest physics blogger on your side?
Act now. Supplies are limited. Allow six to eight weeks for delivery.
drorzel | November 10, 2006I would post some sort of wrap-up about the Lisa Randall chat yesterday, but Discover is broken. They don't have a link to a transcript on the site-- in fact, they haven't updated the front page to reflect the fact that the chat was yesterday, and is now over. There was a link that would sort of give you access to a transcript, but it's broken now, or at least doesn't work in either Opera or Firefox on my home computer.
It's pretty much of a piece with the chat itself, actually-- I thought it was pretty sharp of them to email physics bloggers with invitations to the chat, but the chat itself…
drorzel | November 9, 2006Discover magazine is hosting a live web chat with Lisa Randall this afternoon at 2 pm. Randall is famous for developing some ideas relating to the physics of extra dimensions, and has recently published a popular book (Warped Passages) on the subject.
This is supposed to be a one-hour live chat, with questions taken from the general public. I don't know if I'll have time to drop in (as noted earlier, this is a hectic week for me), but if you're interested in the arcana of modern theoretical physics, check it out.
If they archive it in some useful fashion after the chat, I'll post a link to it…
drorzel | October 12, 2006I'm pretty thoroughly disgusted with the string theory arguments at the moment, so I told myself I wasn't going to say more about the subject. And then, they post a detailed explanation of what strings have to do with RHIC over at Backreaction....
Given my preference for layman-level science blogging over dense technical science blogging, I can't not link to it. If you've wondered what that particular argument is about, but can't make heads or tails of the ArXiV preprints usually offered as explanation, take a look at this post. The English is shaky at points, but that's because the authors…
drorzel | October 10, 2006Lee Smolin's The Trouble With Physics is probably the hot physics book of the year. Granted, that's not saying very much, relative to whatever Oprah's reading this week, but it's led to no end of discussion among physics types. And also, frequently, the spectacle of people with Ph.D.'s squabbling like children, so reviewing it is a subject that I approach with some trepidation.
I'm coming to this late enough that it's hard to talk about the book without also talking about the various responses to the book. I'll do my best to split that material off into a separate post (if I post it at all),…