Since I have control over this blog for a little while (and where is my co-guest blogger anyways?), I figure I ought to use it in my own self-interest. Towards that end, the Austin City Limits music festival is coming up soon, and, as usual, I only recognize a small portion of the bands playing. What should I go see? The lineup is here, and the schedule is here, here and here.
Right now I’m leaning twoards penciling in The Killers in the vain hope that they can pull off a decent live show, The Ike Reilly Assassination, Andrew Bird, Clap Your Hands Say Yeah, Arcade Fire, Regina Spektor, The Decemberists and Bob Dylan. That leaves lots of time for new music, and I turn to you, o internets, for guidance.
I remember back when I was in high school and came across lists of the greatest mathematicians ever. They almost always included Archimedes, Newton and Gauss. Sometimes Euler made it in. I knew who these guys were, but every once in a while, there was this guy I had never heard of, Alexander Grothendieck. I with pretty much no idea what he had done until I hit graduate school where I began to appreciate his contributions to/invention of modern mathematics. I’d like to talk a little about a philosophical aspect of his work here. I don’t know the history so well, and I’m sure all these ideas were developed by a group of people, but I think it safe to say that Grothendieck was central to this.
Continue reading “The Dao of Grothendieck”
The 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 a bit about what perturbation theory is. Unfortunately, most of the equations in classical and quantum physics are not exactly solvable. Often, one can try to solve them on computers, but, particularly in the case of quantum field theory, the calculations can be long and difficult when they are even possible. Faced with this, most of physics (and other fields) is done by a variety of approximation techniques. The most prevalent of these is perturbation theory.
Continue reading “What is String Theory?”
For those of you willing to stay up late, there will be a total eclipse of the moon on August 28 visible to various extents over most of the western hemisphere and some of east Asia. The show is a little late for me (some might call it early) as I’m on the east coast right now, but if you’re up for it, enjoy. After the jump are two photos I took of a total lunar eclipse on 10/27/04:
Continue reading “Turn Around”
Or, “Stealing Chad’s Ideas: First in a Series”.
When you write ‘log’, do you mean base 10 or base e? What field do you work in?
Update: Or base 2 for you CS-types.
As I mentioned earlier, I’m currently attending the Simons Workshop in Mathematics and Physics at Stony Brook University. The weather finally warmed up today, and we relocated to Smith Point Beach to hear Juan Maldacena tell us a bit about AdS/CFT and gluon scattering. If you’re looking for a precis of the talk, I’m afraid I’m not going to give it a try, but I’ll commend you to the paper if only so you can read about the beautiful wire frames.
This is actually the second workshop for me this summer. Before coming here, I had the opportunity to spend three weeks at the Aspen Center for Physics. These workshops have been wonderfully productive and are a great chance to get together with one’s colleagues in an unstructured environment and see what happens. Not that conferences don’t have their uses, but the wall-to-wall talks don’t leave much time for productive work. If you put enough physicists and mathematicians together with a few random chalkboards and whiteboards and nothing else to do, however, great things can happen. And, if not, at least it tends to be amusing.
And there’s nothing wrong with mountains or the beach either.
(incidentally, in addition to funding this workshop and many other worthwhile causes, Jim Simons also got a few friends together to help fund Brookhaven National Labs for some weeks last year.)
The LHC is coming, and it’s time to place your bets. What do you do? (Fun though it may be, shooting the hostage doesn’t really help here.) We’re committed Bayesians (for the sake of this post, at least), and we want to assign a probability that the LHC will see supersymmetry. More generally, we have a set of possibilities for our observable physics, and we would like to assign probabilities to each. This is called the problem of finding a measure. Since the theory of eternal inflation with its “bubbling universes” is the context where the multiverse often comes up, this is often referred to as “measures for eternal inflation”.
Continue reading “Alone in the Multiverse”
I’m here at the Simons Workshop at Stony Brook out on Long Island. I’d like to talk a bit about the workshop later, but right now I just want to note that it is 56 degrees out. In New York. In the middle of August.
Thunderstorms I’d understand, but cold, dreary drizzle? It’s August, not November. I didn’t exactly pack for this.
When we left our story, we were stuck in the unfortunate position of living somewhere in a multiverse without any a priori way to figure out where we live. What might we do?
Continue reading “Twisty Little Universes, All Alike”
Thanx 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.