Saturday, February 25, 2006

As I was reprimanded previously for including some mild swearing in a post which my little cousins read (Greetings from Tokyo C+A) I should warn you that this post may contain a minor profanity. I would however expect to have scared off all but the hardiest reader by that stage.


First, a minor correction. I am informed that Gokukuji is in fact a purely Buddhist temple. The ji at the end of the word meaning temple. A shinto shrine is something completely different and something I am yet to see.


The ladies in the office are clearly worried about who may be lurking around...probably very sensible.


Frustrating indeed. It's five to midnight...I've been waiting roughly six hours for a bit of code to run. It's nothing terribly complicated but something that mathematica doesn't do automatically. Anyway, after 360,000 iterations it finished, and in the split-second it did so, I realised a shortcut, wrote it, ran the program and it took ten seconds...what a strange thing the subconscious is! I hadn't been actively thinking about the problem at all, just getting on with some other work and the idea sprang up, like I'd been mulling over it all afternoon. I love it when the low lying thought processes manage something that with pure logic, my higher level processes struggle over. The most satisfying feeling and one that doesn't happen as often as I'd like but it does occasionally is to go to sleep thinking about a problem and wake up with the answer, seemingly for free.

I'm working on a problem at the moment to do with placing eight dimensional objects into ten dimensional spaces. In fact this is what I spend most of my time doing. I'm attempting to study what happens when you have a few of these lying in different regions of the higher dimensional space. The idea, strangely is that it should tell me something about the four dimensional world of the strong interaction, one of the four forces of nature...

...OK, I've started so I should probably explain what I do in a bit more detail.

(In an attempt at some clarity, I've typed in bold all those parts of this explanation which are vital to get a rough idea what I'm talking about, the rest can be read if you're interested.)

There are four forces of nature (this is my usual opening gambit when asked to explain what I do). There's electromagnetism and gravity, both of which most people feel reasonably familiar with. Then there are the weak and strong nuclear forces which are more to the workings of the nucleus of an atom. In particular the existence of the strong force is the reason that the positively charged nucleus of an atom doesn't blow itself apart in an explosion of protons. The strong force is a strange beast. For a start, unlike the other forces, it gets stronger as you take two objects that feel the force further apart. In fact so much so that you can't pull them apart without creating more particles in the gap in between. This sounds completely ridiculous but there's a nice picture of a rubber band where the force clearly gets stronger as you stretch it.

Anyway, the point is that we have certain techniques for calculating how particles will interact in electromagnetism and the weak force (For gravity we use a different computational technique). When we try and use this methodology for the strong force, we find that the approximations we make aren't valid. This comes down to the fact that the force is strong and we can't in any way approximate it as a small deviation away from no interactions at all (which is what we do for the other forces).

This has puzzled us for a long time and we're pretty stumped when it comes to trying to do calculations of the strong force efficiently
. We can do them on big clusters of computers but it's all pretty messy and we have to make lots of approximations (quarks only come in at tree level, some quarks are very light, others are infinitely heavy).

In about 97, a clever chap called Juan Maldacena made an interesting discovery. He showed that the symmetries of a strongly interacting theory, a bit like the strong force, were exactly the same as those in a ten dimensional theory of gravity. This doesn't sound like much but symmetries are just about the be all and end all when it comes to particle physics. By constraining a theory to have a particular set of symmetries (as well as being unitary, renormalisable and local) the theory is uniquely determined. This is an incredible result of quantum field theories (the method we use to do our calculations).

So, it was shown that there were two theories which look completely different apart from having the same symmetries. In fact they are more closely linked than that. In fact they are two separate descriptions of a stack of four dimensional objects (branes) in a ten dimensional space...I'm often asked what the other dimensions are. The only way I can explain it is to ask "what would somebody who was constrained to live in a sheet of paper say to the same question?". They can't miraculously point in the up-down direction. In mathematical terms it's just as simple to deal with ten dimensions as it is with four (well, not in practice but conceptually it's no harder). In fact in string theory (the area I work in) it's not (always) like we're stuck on a piece of paper. The other six dimensions of the ten are supposed to be curled up in some horribly complicated shape, the form of which dictates the physics we see in the four, non curled-up dimensions.

As a treat for getting this far I'll give you a picture courtesy of Brian Powell's website of the dual descriptions of M-theory:

Sorry, I'm going off track a bit. So there are these two descriptions of four dimensional objects sitting in ten dimensional spacetime. The two descriptions look completely different but have the same symmetries. One of them is a theory of strong interaction, the sort that we have a really hard time dealing with, and the other? Well, the other is a theory of gravity, a complicated one but one that we can do calculations in pretty easily. In fact we can do classical calculations in this theory because all of the unpleasant interactions, which make these theories of gravity into such beasts most of the time, vanish.

So it turns out that by studying a very simple theory of gravity in ten dimensions, we calculate quantities for the four dimensional strong interaction that gave us such a headache in the first place. (It was a clever chap called Ed Witten who showed us practically how to do this. He's quite smart).

I should emphasise: This is amazing! A ten dimensional theory of gravity is equivalent to a four dimensional theory of strong interactions. An interesting philosophical question is: If this equivalence is correct (and we're still not sure), then it is just as accurate to say that the world is described by a four dimensional strongly interacting theory (what we would normally claim) as it to say that the world is really described by a ten dimensional theory of gravity, where the ten dimensions are a strange deformed space with a boundary at infinity and an infinitely massive spectrum of particles? Amazing and indeed bizarre.

(The name of this correspondence is the AdS/CFT duality)

So that's pretty much what I spend my days doing. I'm trying to make this ten dimensional theory of gravity describe the strong interaction as accurately as possible by pushing and pulling the theory around to see where it breaks and where it doesn't.

Fun, fun, fun.

Actually, I love it and wouldn't have it any other way. I understand how fortunate I am that I can spend my days playing around with fun bits of mathematics and complicated theories of physics in an attempt to gain a slight insight into the way our universe is constructed. Though I'm under some pressure to publish papers, I don't have a boss who tells me what I should be doing (except for admin stuff). I can pretty much make my own timetable so long as I'm productive, and I get to go around the world seeing amazing places, meeting great people, talking to audiences who are sometimes interested in what I have to say, and of course eating interesting food.

It appears I am the essence of a jammy bastard.

You didn't understand a word of that, did you?


Japanese TV is truly something to behold...though not for very long. A mixture of bizarre gameshows where half of the people seem to be in hysterics while the other half are hysterical, cooking programs where it seems to be more about the eating than the cooking, a fine focus on the Japanese contestants to the Olympics and Monkey - back by popular demand and one of the most successful Japanese TV shows of all time.

Takeshi Kitano hosts one of the most popular shows and it's strange to see him in his comedy role having seen him so many times in his guise of the violent, silent type.

Speaking of T.K. I'd presumed that the woman on the TV in Battle Royale who introduces the contestants to the game was a characature of the Japanese hosts but in fact this is exactly what they're like, give or take the killing and maiming. In fact it's not just on TV, somehow the language constantly comes over as bubbly, friendly and excitable and as you leave a restaurant or a shop there's a chirpy chorus of arigato gozaimashita (thank you very much) which you echo with similar friendliness. Anyway, all very over the top but quite charming at the same time.

Incidentally, the psycho girl from Kill Bill with the big spikey metal ball appears to be a charming actress in a soap opera here. Another strange shift of perspective.

A lot of the gameshows seem to revolve around one half of the contestants making the others laugh though as far as I can gather, prizes have little to do with it. Yesterday I watched snippets of a gameshow where five contestants were chased for half an hour by a tiny Japanese woman, caught one by one until one was left and was uncatchable. Basically tag on television.

There is almost certainly a lot more to these strange spectacles than I'm gleaning but from my one dimensional perspective, it's all pretty strange.


It's now Saturday evening and I'm back in my hotel room after a really hectic but thoroughly enjoyable day. I'll explain it in more detail pictorially when I get some photos uploaded.

Yesterday I went to dinner with a few of the students and two of the postdocs to a soba noodle restaurant. Soba are traditionally served cold, dipped in a mixture of soy sauce, daikon (white Japanese radish, also sometimes called mooli), wasabi and spring onions (scallions to our US neighbours) and then slurped loudly and enjoyable. This was accompanied with some tempura which again was significantly superior to anything I've had in the UK.

Outside most Japanese restaurants, they have preserved or modelled versions of the dishes so you can see what you're going to get. Generally what you get is identical (give or take the varnish) to what was in the window.

My noodle bingo card was filled this evening with a fine meal of ramen in miso soup.

Anyway, I'll chat more about today tomorrow after my five hour kabuki marathon, if I can keep my eyes open.

Apologies for the rambly and lengthy post.


Anonymous said...

Despite your best endeavour and warnings,Cousin Jon, Anna from a physics diagram, is now liberally using the word Crap, and has demanded I press the fart button postedf on another web site...

Unknown said...

I'm afraid that with everything you taught me at such a tender age, there is only a modicum of sympathy. You see I am only following on the best traditions of familial corruption.


P.S Like you need to be asked to push the fart button!