Category Archives: string theory

So What Is String Theory, Anyway?

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The usual answer you’ll get from the person on the street (as it were) includes lots of nice words about wiggling strings that look like particles, and so forth, and that’s fine. However, the [informed] next level answer, when you’ve worked enough in the field, is that we don’t know. I’ve told you why (at least in part) in previous posts and so I’ll let you read them. We’re still working on it.

While we work, we’ve learned that it is a quite marvellous thing (from the bits of it we’ve come to grips with) that is teaching us a lot about all kinds of physics, and mathematics too. Some of this may be good for describing things about Nature, and we’re still working out lots of that (although see some of the exciting things I’ve been talking about in my previous post and the links therein).

So what do we put on the T-shirt? (You know, the analogue of Maxwell’s equations for electromagnetism – light, etc – that every physics undergrad likes to have on their T-shirt). Well, we don’t know yet.

polchinski what is string theory

But that’s all my opinion. Every now and again it is good to hear from one of the masters about what they think of string theory*, and what it is and so forth. Happily, Joe Polchinski has been known to agree to stand up and give an exposition on this […] Click to continue reading this post →

Brainstorming

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presentation preparation in the sunI had quite a marvellous brainstorming session today. You’ll recall I was preparing a presentation for the February 15th symposium at the AAAS meeting the other day. Well, all of us concerned (the four of us presenting as well as various Brookhaven staff who will take part in the symposium discussion as well) got together over the phone for a teleconference today. It took almost three hours (but happily I was sitting in the sunshine while doing it, as you can see). We wanted to chat about the distribution of ideas and results that will be presented.

There are four of us presenting at the event, with only a short time each to get across some of the key ideas and so we need to make sure that we don’t do too much […] Click to continue reading this post →

Preparation

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Yes, I’ve been a bit quiet of late, I know. I’ve so many things on, both professional and personal that it sometimes keeps me occupied from when I wake up just before sunrise right through to falling asleep a bit after midnight. And yes I know that means I’ve been not getting the traditional full nights of sleep, but if my body insists on getting up at 5:30am, who am I to resist? I thought it was due to jetlag from the trip a couple of weeks ago, but it seems to have taken. I don’t mind too much since watching the light change as the sun rises is a marvellous way to start the day.

clifford johnson preparing slides at the boardAmong the things I’m up to (yesterday and today so far) is a strip-down-and-redesign of a short talk for an exciting symposium that is coming up in a few weeks in Chicago. The American Association for the Advancement of Science is having their big annual shindig there (apparently the biggest science conference in the world) and there will be a number of addresses, plenary talks, and keynote speakers and the like (including Al Gore, by the way), and also several sessions of symposia and other presentations on various topics.

While slightly annoyed at the fact that one major day of the conference is on Valentine’s day (which means I’ll have to be out of town on just the day that maybe, just maybe, on the off-chance, you know – if the universe sneezes or something, somebody might want me to be their Valentine…*), I was looking at that day’s schedule and it caught my eye that there’ll be a session (with several presenters) entitled “The Science of Kissing”, and three hours long, no less:

[…] Click to continue reading this post →

Weinberg on BCS

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For some reason I don’t understand, I occasionally get a copy of some random (as far as I can tell) issue the International Journal of Modern Physics A in the post. It just arrives. The people at World Scientific are presumably hoping I’ll get hooked by it and take out a personal subscription or something. Not sure. Well, it has not happened yet (just as it did not with the unsolicited regular arrivals of Angeleno a while back). But you never know.

Anyway, before putting the one that arrived recently on to my shelf (I can’t easily throw things like that away… it’s a problem, I know) I glanced through the contents to see if there were clues as to why this one was sent to me. I found no obvious ones, but the very first article caught my eye. It was a rather good essay by Steven Weinberg (1979 Nobel Prize in Physics) on BCS (J Bardeen, L N Cooper and J R Schrieffer – No, nothing to do with College Football’s BCS.) theory of superconductivity and the importance of the idea of spontaneously broken symmetry in condensed matter physics and then in particle physics (see last year’s Physics Nobel, by the way). I thought I’d point it out to you, since it is rather nicely written and very instructive (whether or not you’re already familiar with the phenomenon/idea).

He begins with some overstatement, however. He expounds upon the difference between particle physicists and condensed matter physicists and although it is amusingly written in parts (I assume intentionally) he really over-eggs the pudding, in my opinion. Look at this: […] Click to continue reading this post →

Thermodynamics and Gravity

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ads_ballI noticed that Robert Helling shared some thoughts about thermodynamics and gravity today on his blog. He is understandably confused about several aspects of the issue, especially when applied to cosmological issues. (What is the entropy of our universe? Does the Second Law really apply? Does equilibrium thermodynamics even apply here?)

I’ve nothing remarkable to add to the discussion at this time except to note that a blanket statement that thermodynamics and gravity don’t seem to go together (which I don’t think he’s strongly saying) is not one I’d make, since we have a major class of working counterexamples.

The context is the gauge/gravity duals I’ve talked about here a lot, starting with AdS/CFT and beyond. There we know that the gravitational systems are essentially able to display the more garden variety thermodynamics by being immersed in the (regulating-box-like) anti-De Sitter type backgrounds. Then we see that black holes […] Click to continue reading this post →

Gervais and Merchant on Mayo

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ricky gervais and stephen merchant on mayoRicky Gervais and Stephen Merchant were on Daily Mayo for half an hour yesterday. It was a good bit of fun unscripted chatter that’s worth a listen. They were really there to plug the new boxed set of the TV show Extras (which if you have not seen you should put high on your list of viewing priorities – it is quite brilliant), but of course they were also there to mess around a bit.

They asked for a higher standard of question to be emailed in by the viewers, and so I wondered whether anyone would send in some science ones – maybe some physics ones. Sure enough there were. […] Click to continue reading this post →

Southern California Strings Seminar

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Takuya Okuda talking at the SCSS at UCLA, Dec. 2007Takuya Okuda talking about Wilson Loops at the SCSS, UCLA, Dec. 2007. Click to enlarge.

The next regional string meeting is a two-day one at USC, this Monday and Tuesday. It’s going to be full of interesting talks and conversations, as usual. Please encourage your graduate students to come, especially, since special effort is made to make sure that each talk begins with a pedagogical portion to help non-experts in that subfield navigate and see the motivation.

The speakers are: […] Click to continue reading this post →

Strings Everywhere?

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Well, at some point this week I ought to get around to preparing for this. I spoke about the Center For Inquiry before, here. Well, the promised talk that I was going to give at some point is on Sunday. If you’re up for some thoughts about the universe on your Sunday morning, do come along. Details at this link. Some of their publicity is reproduced below: […] Click to continue reading this post →

Summary Strings

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I don’t know if you saw it, but I happened to catch the last two talks of the Strings 2008 conference, via live webcast. They were summary talks. Hirosi Ooguri did an excellent job of summarizing all the main themes in various talks during the conference, and the David Gross summed it all up, took stock of where we are, and where we aren’t, and looked forward. A sort of “state of the union” speech if you like. And the state is good. Very good indeed.

I found these two talks to be excellent, informative, and very interesting. I recommend them to people interested in research in strings and related topics. I can’t see a link to […] Click to continue reading this post →

Bit Like Watching The Olympics…

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(…but without the relentless parade of bikinis, happily.) What am I talking about? You can watch live over the web the proceedings of the Strings 2008 conference taking place at CERN. The official site is here, with links to the webcast, schedule, talk titles, and so forth. (Sorry I’m a … Click to continue reading this post →

Draw

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game of naughts and crosses, spotted in the bar/lobby of an Aspen hotel.I’ve been quiet here recently, I know. Was mostly working, thinking and reading on the weekend. Did not even go on a huge hike (although I did do a nice walk or two). Sometimes, on an evening, I go and read a novel in a bar. (I’m weird that way, I know.) I’ve not been going to the noisy bars full of yelling and the party crowd, but instead like to find a nice sofa in one of the bar/lobby areas of the nicer hotels. Great for reading, and the drink prices are merely extortionate, as opposed to just plain offensive in the more popular places. (Photo: a naughts and crosses game I spotted on a table in one such lobby.)

Well, it’s a draw so far in the battle with my equations and ideas, but I think I’m developing a stronger position. (From this you can deduce that I decided to stick with the same project and hold my ground and struggle on some more.) Perhaps the next […] Click to continue reading this post →

Quantum Black Holes – Why Worry?

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susskind_by_matthew_black for LA TimesWell, you may not have gone to the chat between K C Cole and Leonard Susskind that I mentioned a while ago at the LA Central Library downtown. I couldn’t make it either, being away at the Aspen Center for Physics. I expect it was good. Anyway, I found a little bit of a report on the conversation, done by reporter John Johnson for the LA Times. It is here. (Clickable image of Susskind to the right is by Matthew Black, for the LA Times.)

It gives you some of the simply-stated reasons as to why there was a big argument between Stephen Hawking and Leonard Susskind in the first place (and between several other physicists too… there are hosts of people working on these things, and it took hosts of people to sort it out to where we are now, not just those two, giants though they are). I recommend having a look, as it is especially for the lay-person, and will give you a good idea of what the fuss is about.

You can also see a little bit about his new book on the subject and a link to a video interview with Brian Cox (the physicist, not the actor) at the LA Times blogs here. There are also links to his Stanford continuing education course on quantum mechanics, including the online lectures you can view at your convenience. What a resource!

You might wonder why we care about all this, since currently the only way we know for sure to make black holes in the universe (astrophysical processes making stellar black […] Click to continue reading this post →

Humps

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Now playing: I’m Confessin’ (That I love You), Thelonious Monk [Solo Monk]

Well, I’m now beyond the halfway mark of my retreat and I’ve been on the one project all this time. I’ve made progress here and there, had some setbacks, and have got very stuck at times. It’s just one of those things with this sort of work. Par for the course.

humps in road warning sign, UKThere are times when you think that if you do just a bit more on the project, it’ll get over the hump, as it were, and then coast along. So far I worry that there may be simply an infinite set of equally spaced humps of similar height all the way down the road**, in that every now and again I discover a rather pretty little gem of a result that’s quite encouraging, but these gems don’t seem to have anything to do with each other. So it’s a little scattered gravel pit of gems as opposed to a lovely… Ok, cvj, enough with the gem metaphor.

Now playing: Totem Pole (Alt. take), Lee Morgan [The Sidewinder]

The issue here is whether I should jump ship and use the last of my quality time here […] Click to continue reading this post →

A Hop Over To Canada

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Well, as I said in the previous post, I’m leaving my hideaway/retreat mode and popping over to Vancouver for a short spell to help out at a Summer School. It’s the PIMS (Pacific Institute for Mathematical Sciences) Summer School on Particles, Fields, and Strings. I’m giving four lectures on some of the techniques in string theory that it helps to know in order to do some of the fun things we do to get at interesting physics (such as the topic of the post before). My title is something like “Perturbative and non-perturbative string theory”, and I’ve no clue what the level of the students really is, so goodness knows how far I will get in four one hour lectures. But it does not hurt to try. I’ll be laying the groundwork for several of the lecturers who will be talking about the more advanced stuff closer to their research work, and so I hope to at least help the students gain confidence with ideas and language that will show up all over the place in the two weeks following my presentations.

So what will I cover? Well, I’m going to tailor things to the responses of the students as […] Click to continue reading this post →

Atoms and Strings in the Laboratory?

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depiction of lithium trap from the Kastler Brossel lab in france

A depiction of a lithium trap from the Kastler Brossel laboratory, in France. Details here.

[Despite appearances, I did not choose the music in what is to follow. I just put on iTunes set to random, and started typing, reporting on what was playing as I went along. Nevertheless, there were some nice resonances.]

Now playing: Mr Day, John Coltrane.

So. I must put the Aspen time on hold for a short while, as I promised to give four lectures in Vancouver starting tomorrow. While I sit here in a lounge in Denver at 8:00am, wondering why I booked a 7:00am flight out of Aspen, and also wondering exactly what is in this muffin that I picked up to have with the (rather good) tea they have here this morning, I thought I’d tell you about a little bit of really nice physics that’s going on in the neighbourhoood of my world. Since I’m too cheap and too disinterested to pay for a connection to the web, this’ll only get uploaded quite a bit later when I get a free hookup. (This is a bit more technical in places than usual. Please don’t give up too easily. Oh, and you might have to read some things I point to from earlier to get everything I’m saying – I’m not one for endless repeating myself I’m afraid.)

You can think of this as another story in the line of development I’ve been pushing (and telling people about here and elsewhere) for many years now. Applications of string theory to a broader range of physics areas than the popular discussions of the topic seem to touch upon. I told you last year about the exciting work going on in understanding properties of new phases of nuclear matter being unlocked at the Brookhaven experiment RHIC (colliding heavy nuclei together to create a sort of hot quark-gluon soup). That work continues. This new work pertains to experiments as well, and this time, these are closer to the human scale bench top experiments we all get misty-eyed over (ok, I do, maybe no-one else). It is super-cute stuff. I should […] Click to continue reading this post →