Aaron
bergman | September 9, 2007Well, Chad's back, and I guess that means that this guest-blogging stint has come to an end (free! I'm free!). I want to thank Chad again for the opportunity to play in his sandbox for a few weeks. I didn't get the chance to write every post I had planned. Real life -- or at least the closest academic imitation thereof -- does sometimes get in the way of blogging. Anyways, having seen it from the other side now, this blogging stuff isn't easy. I don't know how Chad manages to come up with two or more things to say every day, but I guess that's why he's the blogger and I'm the guest-blogger.…
bergman | September 8, 2007I remember the last time I saw the milky way. I was at my aunt's house in the foothills of the Sierras, and late at night the dense river of stars emerges. But that is still not the true milky way, or so I hear. And, in more urban areas, the detritus of our incandescent society reduces the night sky to an inchoate glow. This article in the New Yorker talks about the poorly designed night time illumination that has resulted in our current situation, and what can be and is being done about it.
(via Slashdot)
bergman | September 6, 2007Now that I'm back in College Station, it's time to start getting applications ready for the great job search. I don't know how it is in other fields, but in math/physics, this generally involves three to four letters of recommendation, a CV, a research statement, sometimes a teaching statement and maybe an annotated bibliography. In high energy physics, we have the Theoretical Particle Physics Job Rumor Mill run by the now nonymous John Terning. In addition to listing offers and educated guesses at short lists, it also serves as a nice clearinghouse of positions. SPIRES, the APS, Physics…
bergman | September 5, 2007Steinn reports that the NRC has made its recommendations for NASA's Beyond Einstein program. The winners appear to be LISA, a gravity wave observatory, and JDEM, a competition of dark energy focussed satellites. Steinn has lots of links to the various projects. The executive summary of the report is availabe here (pdf).
I know next to nothing about these things, but from afar it always seemed like LISA was one of those neat ideas that was never actually going to happen. The basic idea is to put three satellites in orbit around the sun and bounce lasers around to measure gravitational waves.…
bergman | September 5, 2007Well, I'm back in Texas and just in time for Steve Jobs to introduce new toys I can't afford. At the risk of turning Chad's blog into an Apple advertisement, every time I pass an Apple store, it takes significant willpower to not walk out of there with a new iPhone. I find it endlessly amusing to load up my papers on the demo models -- yes, I am easily amused. A certain theorist was showing his off at Aspen, too. Well, you don't want a phone with your iPod? You can now get an iPod touch, WiFi included. 8 and 16 gigs. iPod Nano? Smaller with really tiny video. Old school iPods? 160 gigs now.…
bergman | September 3, 2007Happy Labor Day to everyone. I'll be traveling back to Texas, so no blog for me for a day or so.
bergman | September 2, 2007Because my team, the Forty Niners, aren't. Neither apparently is Michigan. On the other hand, my co-guest blogger is surely happy.
bergman | September 1, 2007The Principles proprietor is currently at WorldCon where the Hugo awards are given out. This year's winners are available (among many other places, I'm sure) at Patrick and Teresa Nielsen Hayden's blog. I wasn't a huge fan of Rainbows End myself. I did like "The Girl in the Fireplace", a Doctor Who episode. The writer, Steven Moffat, also wrote "Blink", this season's best episode.
bergman | September 1, 2007Taking a break from all this physics, I thought I'd talk a little about music and some related mathematical coincidences. One of the fundamental concepts of music is that of consonance and dissonance. Consonant things sound nice when played together and dissonant things do not. For example, if you play two Cs together on a piano (or your instrument of choice), it's a pleasing sound, but playing a C and an F# together sound unpleasant.
It could have been the case that what we find pleasing and displeasing on this simple level could be purely random, but our tastes align with a very elementary…
bergman | August 31, 2007If you're on the west coast tonight and are willing to stay up late or wake up early, you have the chance to see the Aurigid meteor shower. This shower is fairly unique because it arises from a comet with a period of around 900 years. Some people have even claimed that there's a chance this could be spectacular, but these predictions are often wrong. After the disappointing Perseids, I'd love to be able to stay up for this one, but I'm still on the east coast. Ah well. Maybe some other shower.
bergman | August 29, 2007Since 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…
bergman | August 27, 2007I 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…
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 25, 2007For 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:
bergman | August 24, 2007Or, "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.
bergman | August 23, 2007As 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…
bergman | August 22, 2007The 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…
bergman | August 21, 2007I'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.
bergman | August 21, 2007When 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?
One thing we can do is let the dreaded anthropic principle rears its head. At its most basic essence, the anthropic principle is the statement that we exist. This is data, and we can draw conclusions from this data. The most famous examples of this are Hoyle's prediction of a particular nuclear resonance based on the need for enough carbon in the universe for us to exist and Weinberg's bound on the cosmological constant…
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.