Category Archives: work

That Sort of Time

By | | , , ,
1 Comment

Yes, it has been that sort of time. The last several days have been full of far too many things – several of which it would be fun to blog about – but none of which have left me any time for doing the actual blogging part. What sort of things? Well, everything from social gatherings like a couple of parties and salon-type events on the one hand, the usual work-type events on the other (like yesterday’s reception to welcome new USC College faculty – I find those especially important to show up to as a means of re-engaging with a cross section of one’s colleagues, old and new, at the beginning of the year*), and on a third hand (sorry) there’s been a big crunch on the research side of things. The big crunch saw me in my office until about 3:00am after a long night of finishing up two companion papers with three of my students (this included breaking for a walk across campus at about 8:30pm to get some tasty mulitas at the excellent La Taquiza) and submitting them to the arXiv. Sensibly, the students went home by 1:30 or so, leaving me the silly one to tinker some more until the end. It was a really fun couple of projects uncovering some rather rich physics, and I’ll try to tell you about them some time soon.

So anyway, my plan today was to write you a 9/11 post, but not quite about what you […] Click to continue reading this post →

Switching

By | | , , ,
7 Comments

Back in LA, and down at the USC campus. Good to be back! Click below for larger view.

campus overhead from google maps Well, it is the first day of the new academic year’s teaching cycle. I’m here in my office at 7:30am (the power of jet-lag) and somehow have to switch my mind back firmly onto teaching and other matters. It’s always tough to do this, since there are always lots of intensely interesting research issues that continue on my mind from the Summer, and I know that some of those will gradually begin to fade (if I am not careful) as my other duties take up so much of my day to day. My first class (part one of the upper level electromagnetism course) is at 10:00am, and I want to plan out the structure for the whole semester, and write a syllabus to hand out and discuss. As well as the first lecture, of course. I’ve not taught this part of the cycle before, and so I’ll have to be writing new lecture notes.

I want to try some new things this year. In particular, I’ve become increasingly concerned […] Click to continue reading this post →

My Superpowers Revealed

By | | , , , ,
6 Comments

Ok, I can’t resist. From an earlier post:

…and of course video footage of me effortlessly squashing a star much larger than our own sun down into a tiny space should help out enormously later on with classroom control, and so forth…

Since my cover is now blown, here are some stills** (click for larger) from Tuesday’s (unexpected) episode of the History Channel’s “The Universe”*: […] Click to continue reading this post →

News From The Front, VI: Simultaneity

By | | , , , ,
7 Comments

aspen from gondolaI stopped the previous post rather abruptly (I had to do another task and then run some errands) without getting to tell you a little twist at the end of the story. Here it is.

Having chipped away at the thoughts that Strominger’s talk stirred in my head for several days last week, scribbling equations to check that all I was thinking was on the right track (and chatting a couple of times with Nick Halmagyi), I decided that it was all fitting together so nicely that the framework and my extensions of it just had to be true. There was that feeling that it was too nice to be wrong, and it passed all the obvious checks I could think of. There were two independent consistency checks everything had to pass (using my way of formulating things) and they gave exactly the right results as required by the general setup, with no room for maneuver.

When that happens so nicely, usually at that point in thinking about a physics problem, a thought occurs to me. If I’m playing with a good idea and everything is working so well, then there’s at least 200 other people in the field who probably are also playing with it, and 199 of them have way more time than I do to think it through and write it up before I can. One should not really worry about these things in an ideal world, but I’d be lying to you if I said it did not come up as a concern from time to time. I’ve a history of having my thunder stolen out from under me several times in the field (and not always accidentally), so I’m a bit gun shy.

Anyway, I started writing a draft of the paper on Thursday the way I usually do: I write […] Click to continue reading this post →

News From The Front, V: Microscopic Weekend Diversions

By | | , , , ,
5 Comments

I’ve been spending the day so far as an administrator, and not a researcher, since I have to present the results of two committees’ deliberations at one of the big annual organizational meetings tomorrow here at the Aspen Center for Physics. So I’ve been gathering and arranging data in a presentable form. Enough. I will take a break and blog a tiny bit before turning to a truly riveting task – reviewing an introductory physics textbook for a publisher… (Sigh…it is not so easy to escape these things out of semester time.)

I had big plans to do a hike each day on the weekend, but physics intervened. I should explain a bit more. Earlier last week I eventually got around to following Nick’s suggestion from an earlier post to take a look at Andy Strominger’s Strings 2007 talk entitled “Search for the Holographic Dual of N Heterotic Strings”. It was the usual nice Strominger talk, where he motivates the physics very well, and presents interesting and clear D-branesthoughts on the problem in hand. I shall try to say a bit more about what it is about later on, but the general gist of it is that it is to do with understanding certain types of four dimensional black hole in string theory. As you may know, one of the extraordinarily successful results in string theory in the last decade (and slightly more) has been that we can understand one of the most central results of semi-classical quantum gravity -that they have an entropy and behave like thermodynamical objects (the work of Bekenstein and of Hawking from the early 70s)- in precise terms in the full theory of quantum gravity that string theory appears to present us with. This started with the work of Strominger and Vafa in 1996, that showed how to describe a large class of black holes as essentially made of extended objects called D-branes (about which I’ve spoken at length earlier1).

Just to fill in the gaps roughly: Hawking’s result that black holes can radiate as thermodynamical objects comes from taking Einstein’s theory of General Relativity and combining it with Quantum Mechanics in a partial way. He could not really do much better since there was no proper quantum theory of gravity at the time, but even in […] Click to continue reading this post →

More Than A Hint Of The Old Days, II

By | | , , , ,
18 Comments

A strange but satisfying aspect of my time here (I’m at the Aspen Center for Physics, recall) has been the fact that due to some odd serendipity, there’s a ton of people from the “old days”. Which ones? My Princeton years, in the early 90s, as a postdoc at the Institute for Advanced Study (and later at Princeton University). These are not all people doing what I do, but in a wide range of fields such as high energy physics, astrophysics, condensed matter physics. Several of us were postdocs together. I’ve been chatting with people I’ve not seen for a while, sometimes not since those days, or they are people I met back then, and with whom I have a pool of shared memories from those days. So it has put me in mind of those times somewhat.

A quick example. Soon after I arrived last week, I was walking along, chatting with Petr Horava (Berkeley) about various things, and we got on to reminiscing a bit about our time together as postdocs in Princeton. And then minutes later, as though conjured from the very substance of our conversation, who should walk by but one of the Gods/Legends of the field (then and now), Princeton’s Alexander Polyakov. He walked by in exactly the same sort of way he would back then, either coming from or going to a walk along the river or canal, perhaps to give us a lecture. Petr and I looked at each other, and continued our walk and talk.

The great news for me last week was that Polyakov then gave a talk. I’ll admit to being a big fan of his physics. When he gives a talk nearby, I show up, no matter how confused I might end up at the end. There’s going to be good stuff in there – it’s only a matter of time before it sorts itself out in your head. Often years. Decades. Several of us sat in on his graduate class back in Princeton in the early 90s just to try to catch the pearls of wisdom which we’d pick up as he lectured on….. Well, I’ve no idea to this day what the class was really about. He would show up (probably fresh from a walk), with no notes or anything, and just pick up a piece of chalk, stare out the window for a few seconds, and then start writing stuff. Essentially, he was randomly jumping around the subject matter in his widely under-read book “Gauge Fields and Strings”. He was all over the book. It was not always a simple and coherent path through the subject matter, and it seemed that he was largely exploring whatever took his mood in the moment, but I suspect that was largely my ignorant young mind’s impression.

Polyakov in Aspen
A. M. Polyakov in the middle of giving what for me was an excellent and intriguing seminar at the Aspen Center for Physics. Click for larger view.

Sadly, it is the type of course that these days would score close to zero in most […] Click to continue reading this post →

All In A Day’s Work

By | | ,
10 Comments

Difficult to say what a typical day is at the Aspen Center for Physics. It probably varies a lot from person to person, since many people are here for different reasons, and with different goals. There’s a lot of sitting and thinking, and walking and thinking. There’s a lot of chatting in corridors, and at blackboards. There’s quite a buzz of productivity during the middle of the day. On some days, there might be a couple of seminars, where someone presents finished work or work in progress. Here’s Robbert Dijkgraaf (University of Amsterdam) leading a discussion of some of his recent work today:

Robbert Dijkgraaf at Aspen

In addition to some seminars, my day was filled up a bit more with some administration. I’m on a couple of committees that helps keep things ticking along […] Click to continue reading this post →

Strings 2007: Share the Memories

By | | , ,
6 Comments

trees near the aspen center for physicsA big chunk of yesterday (recall, I’m visiting at the Aspen Center for Physics) was spent chatting with old friends in the field I have not seen in a while, including going for a walk or two in the local surrounds with colleagues, discussing some of the physics issues of the day.

One of the things that comes up a lot with everyone I spoke to (and met at lunch, and in corridors and so forth) was Strings 2007, the big annual meeting that was held in Madrid last month (blog post here). It comes up in the form of people asking each other things like: “were you at Strings?”, “what did you think of Strings?”, “what were your favourite talks?”, “is there any interesting gossip about…?” (where the latter is not necessarily directly about physics).

So it occurred to me that some of those conversations and responses might be useful to workers in the field. Of course, you can just sit and work your way through the entire collection of online talks, a good thing to do. But it’s interesting to hear from others what talks they liked, and why, just as we do (and maybe have done) over tea and coffee in lounges all over the world after someone returns from a meeting. Often, this is where we hear of some excellent work by the less famous speakers (or even by someone who did not talk at all), etc.

So I’ll kick off. Although I was not there, and have yet to start a serious assault on […] Click to continue reading this post →

Physics, 101

By | | , , ,
4 Comments

physics at 101 cafeIt’s been one of those days. I just got back home, at 2:30am, after a very pleasant bit of work in a cafe. I was writing up my thoughts of the day into my notebook (I’m old-fashioned that way) and crafting new ones. Where was I? The 101 Coffee Shop, of course, an LA landmark – with those lovely booths, the counter, the lighting, all classics – over near the Capital Records building (another LA landmark) just where you join the 101 heading up to North Hollywood – hence the name, and hence the title of this post.

It’s been one of those days in a good sense. After a long couple of weeks of muddling and being rather down about a project I’m working on that had run into problems, things suddenly made sense today over the course of a long IM conversation (six hours) with one of my collaborators, Jeff Pennington. Things just started to fall into place during the brainstorming… we’d exchange facts and observations, explain thing to each other….muddle along for a while… ask questions… calculate separately for a bit…. suggest computations to each other…report results…get confused… and then it all broke open quite nicely and every single fact seemed to fit into place by the end. A lot to do still, but it seems rather robust and tantalizing.

After taking a break after the long brainstorm to do a bit of gardening work, this […] Click to continue reading this post →

Consider a Spherical…

By | | , ,
11 Comments

So I went out to get a new kettle a few days ago. I’ve now given up on a rather lovely design by the company Chantal that I’ve been using for many years since on two models in succession (or is it three?) the same flaw has revealed itself – the plastic parts of the Hohner whistling lid began to loosen gradually (probably from too much heat up the sides, which may be my fault) and then you eventually end up with a non-fitting non-whistling lid.

I began to assess other kettle designs, and in doing so found myself thinking idly about a number of physics issues. One of the main ones was energy. If I got a smaller kettle (the one I had before had a capacity of 1.8 quarts, and I was considering ones as big as 2 quarts and ones as small as 1.5 quarts), which I was leaning heavily toward, it would probably encourage me to save energy and not boil so much water. On the other hand, maybe that’s really silly, since I might just be putting the same amount of water into the kettle anyway… I’d never fill either up all the way in any case. But if I put the same amount of water into both kettles, would the smaller one end up using less energy anyway as I don’t have to heat up the extra air in the chamber, or does that not matter…? It’s not that simple since the chamber is not sealed. Hot air (and later, steam) is escaping all the time. Well, this is all complicated by the fact that the smaller kettle has less of its base in contact with flame, so I’d have to turn down the flame, and heat it for longer on a lower flame than with the larger kettle… would that make a difference? Perhaps a smaller chamber at lower flame means slower steam escape velocity, and so a quieter whistle. Not good if you’re prone to forgetting that you’ve put the kettle on during an absorbing computation…downright dangerous, in fact!

This was not an entirely serious discussion, you see, but it’s sort of fun sometimes to find these things floating around in one’s head. Physicists (and I imagine, other scientists) have this sort of thing flit through their heads a lot. The key thing -especially as a Theoretical Physicist- is knowing when to engage with one of these problems, and when to ignore them. Is there are clear route to tackling the problem? Is it worth it? Is there something to be learned from solving this problem that might be useful elsewhere? In fact, I was trying to explain this all to a writer friend of mine […] Click to continue reading this post →

Strings 2007

By | | , , ,
7 Comments

goya strings The main annual conference in my main field of interest starts today. Strings 2007 is in Madrid, and runs all week. The website is here (while there, have a play with the front page image of the Goya painting – quite entertaining). They promise to update the schedule/speakers page with scans of slides, and video, so you’ll be able to keep track of some of the new developments online. There’s no system for doing this live, or asking questions remotely, so if you want to quiz Ed Witten about his new 83-page monster paper on three dimensional gravity that came out yesterday (just in time for the conference!), or feel the buzz of event-anticipation whenever Witten talks about huge new sets of results, you’ll still have to show up in person.

Why am I not there? Well, it would be nice, but there are lots of reasons I’m not going […] Click to continue reading this post →