point to Occam 28 February 2007
Posted by DSM in mathematics.comments closed
Yesterday there was a very good talk on the computability of Julia sets at the dynamics seminar. The presenter was originally from Canada — well, Toronto anyway — and was an excellent speaker; I don’t know if those two are related, I’m just sayin’, is all. At one point, he tried to establish how much the audience knew about Julia sets and how much he’d have to explain. Almost all of the audience said they knew what they were, which was good because then he could concentrate on the relevant points and not give a minitutorial.
He couldn’t help himself from asking one test question of the crowd, though:
“What’s your favourite Julia set?”
“The circle,” said one professor.
[For nonmathematicians: at this point the room erupted in laughter. --ed]
“Good answer,” was the reply.
True story! The seminar was given by Michael Yampolsky of the U of T and ETH Zurich, describing neat work he’s done with his grad student, and some counterintuitive results they’ve found.
quantum green 27 February 2007
Posted by DSM in daily life.comments closed
After a meeting with the supervisor this morning I came back to the office, only to find it locked. My officemate had gone for lunch.
Problem: I couldn’t find my keys. Looking at my desk through the window I saw the green of my keychain. I leaned my forehead against the glass with its graph-paper squares and decided to wait until the boss came by — he’d said he was going to drop by the office. But he’d also mentioned he was hungry, so if he’d decided to get something to eat first, I’d have to wait until Arnaud got back..
Besides, I wasn’t sure if he had a key which was strong enough to open this door. Back in my grad student days pretty much anybody could get in and/or let me in to my office, but times have changed, and they’re pretty security-conscious around here as a result of lots of thefts. We have to carry around an ID card all the time (in principle we’re supposed to wear it visibly) or security guards will challenge our right to be on-campus.
In fact, in order to get into my office after hours, you have to first get through the outer doors which open only if you have the right code on your card. Admittedly you can often socially-engineer your way past it (i.e. look like you belong and walk through behind someone else, about the easiest kind of soc-eng imaginable). Then you have to get past another carded-door, which is much harder to sneak through because we know everyone who should be in this wing. And then you need an ordinary key to get into the office. Even after all that, when I’ve been working late, I’ve had guards come by, knock on the door, and ask to see my ID. Apparently I don’t look nonsuspicious enough for a pass.
In any event, miraculously, just as I was about to lose all hope, I glumly reached into my pocket.. and found the keys! The green on my desk wasn’t the green from the keychain, it was the green from the bottlecap on a Tropicana Go! orange and pear drink.
I think the moral of the story is that if you’re careless enough to forget your keys, then you may be equally capable of mistaking bottlecaps for your keys, and failing to find your keys even if you’re carrying them. So don’t give up too easily when all looks lost: it’s possible you’ve merely made more than one mistake and they’ll cancel out.
Hey, it’s a Tuesday. Not the most exciting day of my week.
probably wouldn’t have worked out anyway 24 February 2007
Posted by DSM in QOTD.comments closed
“But, in truth, she was a combat waitress from the future.”
the boredom of the guard 23 February 2007
Posted by DSM in academia.comments closed
Had to invigilate a graph theory exam this morning.
(As an aside, they say “sitting exams” here. In Canada, if you use “sitting an exam”, everyone will know what you mean, but it can sound.. not quite pretentious, exactly, but a little unusual. One thing which takes a little getting used to is that many English expressions sound like a marker of high social class to the Canadian ear, but here they’re used by everyone.)
Fortunately my officemate got an email reminding him of his exam duties earlier this week or I’d have missed it. I asked last week if I had any responsibilities, and was told that if I hadn’t already been informed then I was probably safe. Well, it turns out I had been assigned a section — but the information came in an attachment to an easily-ignored message over a month ago! My memory doesn’t work on those timescales. Maybe it’s time to start using the e-calendar software..
Watching over students who are writing exams is pretty boring, but you usually find a couple of students trying to get away with things. One kept looking at the exam beside him to the left and then writing; after he noticed that I was watching, he didn’t write much for the next twenty minutes except doodles. I couldn’t believe how unsubtle he was. Then the student on the left of the guy that the would-be cheater was trying to copy from did the same thing, made an unhappy face, and scratched out his own work — he must have decided that the central guy was likelier to be right. (It was a list of graph nodes or edges or something.)
Originally I’d thought that the guy in the middle was innocent, and merely couldn’t be bothered to hide his work — after all, he shouldn’t have to worry about stuff like that — but from the conversation between the three of them afterwards I suspect they knew each other.
The first cheater didn’t spend much time writing, so I’m pretty sure he failed. But I set the three exams aside to be marked in tandem, just in case, and made it obvious to them that I’d set them apart. I thought of nodding to them and saying something like “Gentlemen” when I collected the exams, but I don’t know if it would have been appreciated..
One student arrived with about ten minutes to go in the exam and explained that her alarm hadn’t gone off. Thankfully I could push that decision up the ladder. I hate dealing with squishy discretionary stuff like that.
Finally, towards the end of the exam, one student decided that since he was done he could start messaging people. And then to try a “you’re-being-unreasonable” face when I tell you to stop? Attempts at petulantly taking offence aren’t going to work with me. I’ve been teaching since you were ten, kid.
Babysitting.
Bah.
on physics and being a squire 22 February 2007
Posted by DSM in physics.comments closed
I forgot to mention how the EPSTAR three-talk evening went. It was pretty good, even though we showed up awfully late and so had to speed-drink our coffee to make it inside in time.
Peter Coles’ talk on dark matter and dark energy was a pretty standard introduction to modern cosmology, but it had some cute notes. My favourite note was his reading of a classic painting of medieval cosmology — Christ surrounded by angels in Heaven, and Hell in the foreground/bottom — in which the angels were mapped to postdocs. He ended with a quote by noted philosopher Donald Rumsfeld:
As we know, there are known knowns. There are things we know we know. We also know there are known unknowns. That is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know.
For reasons I’ve never fully understood, the Left seems to find this quote amusing. But it’s not only clearly true, it’s insightful: the unknown unknowns are the things which wind up killing you, because you can’t plan for them. Rumsfeld is spelling out for people the intelligence challenges of war. Is it just that there are lots of repetitions of versions of the word “know”, apparently too many to keep track of? Is it that they remember repetition from poems and stories in childhood, and so any examples of it make them think of nursery rhymes? Or is it that they hate Rumsfeld, and therefore if he says something which they don’t immediately understand, it must be funny-stupid?
Michael Green’s talk on string theory was fine, but it was mostly a history of particle physics and the GR/QM inconsistency with a few minutes of “.. and now instead of treating particles as points, we’ll consider them extended stringy objects” tagged onto the end. Bryan Webber’s talk on cutting-edge particle physics was actually the most interesting material to me because I don’t know much about the specifics of what’s going to happen at the Large Hadron Collider, and he showed lots of graphs with exclusion curves and permitted regions. I’d even forgotten, for example, that the best-fit model for the Higgs was already (mostly) excluded.
My private hope is that they don’t see evidence of supersymmetry.. just because I know that will annoy a lot of people, and I’m a terrible, terrible person. Even if they did, since there are supersymmetric nonstring theories, it wouldn’t be conclusive evidence in favour of string theory as several pop articles I’ve read suggested. I would’ve liked to ask Michael Green if there are nonsupersymmetric string theories waiting for their day if the LHC rules out anything like the minimal supersymmetric models. Probably; string theorists are nothing if not creative.
The next day, last Thursday, I was talking to a friend when I suddenly realized that if I didn’t sprint I was going to be late for Sir Roger Penrose’s second twistor theory talk. Bashed my knee into concrete while running over, cutting myself pretty badly — still hasn’t healed — and tearing my favourite jeans.
When I made it into the physics building, I ran to the elevators, and found a short, well-dressed man looking somewhat lost. He was also planning to be at the talk, but wasn’t sure where it was: the last time he’d come he’d been escorted. I told him where it was, and waited for the elevator with him, and then led him to the room to make sure he found it.
So I guess my being somewhat late worked out okay, because the lost guy was Sir Roger himself.
Not exactly the stuff out of which legends are made, but we do what we can.
dust to dust 21 February 2007
Posted by DSM in faith.comments closed
Today is Ash Wednesday, the beginning of Lent, and a time when you make a special effort to do some interior scrubbing. It’s also a tradition to give things up — and as Fr Jones explained on Sunday, a sacrifice which doesn’t cost you anything isn’t worth making. (I don’t think the suggestion to abandon watching Coronation Street and Eastenders really applies to me.)
I quite like the day’s rite, when the ashes are imposed and the ancient words are spoken to remind us of our mortality: Remember, man, that thou art dust, and unto dust shalt thou return.
I always wonder whether I should wash the ashes off, with Christ’s famous warning in mind:
Beware of practicing your righteousness before men to be noticed by them; otherwise you have no reward with your Father who is in heaven.
[...]
Whenever you fast, do not put on a gloomy face as the hypocrites do, for they neglect their appearance so that they will be noticed by men when they are fasting. Truly I say to you, they have their reward in full. But you, when you fast, anoint your head and wash your face so that your fasting will not be noticed by men, but by your Father who is in secret; and your Father who sees what is done in secret will reward you.
On the other hand, the wearing of the ashes and the carrying of palm crosses on Palm Sunday serve as quiet, wordless witnesses to the Faith. I used to have students ask about the ashes every year. (For some reason I always used to get assigned Wednesday tutorials.)
I finally settled on a way of handling the problem. As GKC noted:
Becket wore a hair shirt under his gold and crimson, and there is much to be said for the combination; for Becket got the benefit of the hair shirt while the people in the street got the benefit of the crimson and gold. It is at least better than the manner of the modern millionaire, who has the black and drab outwardly for others, and the gold next to his heart.
In this spirit, I think it works well to have a public sacrifice related to your public life, which your friends can watch and call you on, and a private sacrifice which you don’t talk about, and no one will know but you and God.
One year I gave up meat, which was rough.. my diet is pretty meat-heavy, and several times I found myself having to explain that no, I wasn’t a vegetarian, which I found profoundly embarrassing.
This year I’ve decided to give up all food and drink which isn’t necessary, and simple. No more midafternoon snacks; no carbonated beverages, even with meals; no twice-a-day coffee; and definitely no beer. Including the beer which the department pays for on Friday lunch with the visiting speaker. For the next forty days and change, it’s bread and water (metaphorically) for me, eating only because of hunger and drinking only because of thirst.
We’ll see how it goes.
golfing for dollars 20 February 2007
Posted by DSM in politics, sports.comments closed
Work is continuing to expand to fill all available time. But it’s going very well — every crazy thing I try these days seems to work, even coming up with stranger and stranger transition functions for my integrations — so I shouldn’t complain, even if it interferes with my blogging! (And my email replies. Sorry again to everybody, but it’s partly your own fault for sending twenty-screen messages that take hours to respond to..)
I had to link this, though: Tom Sowell is a treasure. (I think that line’s due to Jay Nordlinger.)
San Francisco has six municipal golf courses — and they are losing money. Now there is all sorts of hand-wringing over what to do about it.
An economist might see this as a non-problem. If the golf courses are losing money, then get rid of them. Given San Francisco’s sky-high land prices, selling the land that the golf courses are on would bring in millions, if not billions, of dollars.
But such advice is why so few economists get elected to political office.
A politician has to be all things to all people — a friend of the golfers, a protector of the workers who maintain the golf courses, and of course a believer in mother and apple pie.
Even the suggestion that the golf courses might be turned over to some private operator of golf courses has caused opposition. One golfer declared: “Privatization would raise greens fees. Nobody could afford it.”
This is the kind of talk that has to be taken seriously by elected officials, even if an economist would dismiss it as sheer nonsense. Have you ever heard of any business raising its prices to the point where it no longer had any customers?
Read the whole thing and enjoy the clear-headed conclusion:
The great allure of government programs in general for many people is that these programs allow decisions to be made without having to worry about the constraints of prices, which confront people at every turn in a free market.
They see prices as just obstacles or nuisances, instead of seeing them as messages conveying underlying realities that are there, whether or not prices are allowed to function. What prices are telling San Francisco is that municipal golf courses cost more than they are worth — not in my opinion, but in the actions of people who are spending their own hard-earned money.
the next stage of human evolution 15 February 2007
Posted by DSM in miscellanea.comments closed
I’m one of the many people who has what’s called the “photic sneeze reflex“, or “Autosomal dominant Compelling Helio-Ophthalmic Outburst syndrome” (check the acronym). That is, I sometimes sneeze when going from a dark space into a bright one. With me it’s typically two, sometimes one, and very, very rarely three.
They claim it’s probably a defect in which “overstimulation of the optic nerve triggers the trigeminal [sneeze-controlling] nerve”.
Myself I think an Outer-Limits-style explanation is probably more likely, and definitely more fun.
For example, it could be a long-dormant mutation encoded into our DNA by ancient alien visitors who live in worldships made of light. Those of us who “suffer” this “condition” are really just farther along in having our brains prepared to commune with their mindpools in which light and thought become one.
Just goes to show that if astronomy doesn’t pan out, there are always other options. Ascended ambassador to energy beings, for example.
(Hat-tip KenJen.)
nonperiodic tilings of the plane 14 February 2007
Posted by DSM in astronomy, physics.comments closed
[Currently playing: "Love is All Around", a version of which was used as the Mary Tyler Moore theme song. Turns out to have been written by Sonny Curtis, who also wrote "I Fought the Law". The things you learn from listening to the Diner!]
This week’s full of a lot of talks to launch EPSTAR, the Experimental Particle, String Theory and Astronomy Research consortium — although by astronomy they have in mind cosmology and not planetary dynamics. Professor Sir Roger Penrose, Fellow of the Royal Society, Order of Merit, as he’s formally introduced, is the Very Special Guest.
On Monday he gave a public lecture on “Before the Big Bang”. I tried to record it but something went wrong, which is too bad: think what a bootleg copy of a Penrose talk could bring on the black market! [nothing --ed. spoilsport! --me] He presented various ideas of different levels of plausibility about what (if anything) happened before, and whether or not there were ways to mathematically continue the models past/through/around the initial singularity, assuming there was one. Much of his talk was actually focused on what happens at the hypothetical heat death of the universe, and considered whether in a massless and radiation-dominated regime, the inability to construct a clock (because you don’t have any mass out of which to build anything) means that the standard picture of spacetime will break down in a way similar to the way we expect it breaks down at the earliest period of the universe. (Richard was also there, and he wondered if Penrose’ ideas required proton decay or not. Penrose was ambiguous on this point.)
The hall was packed — the cult of (scientific) celebrity, as someone said — and either the British education system is better than I’ve been led to believe or he may have aimed high in assuming that the audience was comfortable with conformal transformations. (Mappings which preserve angles, both magnitude and direction, but can let other things like size vary.)
Yesterday he gave another talk, a longer and more technical lecture, on his pet idea, twistor theory. Room was also packed: people were standing. The algebra was pretty rough slogging unless you’re more used to working with spinors than I am, but you could follow the overall argument well enough if you paid attention. I think I’d have been completely lost if I hadn’t reread chapter 33 of his book “The Road to Reality” beforehand: he stayed pretty close to his presentation there, just with more of the details.
He had a cute line about first cohomology, also from the book: it’s a precise, nonlocal measure of the degree of physical impossibility of an object, and gave the impossible triangle as an example. Locally, the triangle’s perfectly constuctible — there’s nothing weird about it. And if you remove a corner, you can build it. But you can’t build the object as a whole, and that impossibility of globally satisfying certain connection constraints is what first cohomology measures. (The triangle case is a particularly simple case of this.) He noted that he didn’t know of an equivalent easy way to explain second cohomology, but that just as twistors are naturally useful for dealing with 1-particle wavefunctions because of their first cohomological properties, to handle such things as EPR entanglement second cohomology may be important.
He intermittently returned to the GR/QM unification theme, and suggested that his twistor program (in which the lightcone stays fixed but the idea of an “event” gets fuzzy) has advantages over some other proposals (in which the lightcone gets fuzzed up) as a road to quantum gravity. I’ll go back on Thursday for part two.
In an hour or so the lectures start up again, but no Penrose today. Instead it’s Peter Coles, once of Queen Mary and now of Nottingham, on dark matter and dark energy; Michael Green, once of Queen Mary and now of Cambridge, on string theory (yeah, that Michael Green); and Bryan Webber, never of Queen Mary and now of Cambridge, on the frontiers of particle physics.
Should be fun!
that goes without saying 13 February 2007
Posted by DSM in QOTD.comments closed
“They’re called Quilty, as any Scandinavian Irish trad group should be.”
and that’s the truth 10 February 2007
Posted by DSM in physics.comments closed
Drowning in work — and it’s going well, so I think I’ll just keep inhaling the H2O for a while. Apologies to all my correspondents.
This, however, deserved a quote. From Peter Woit’s review of Nick Evans’ new novel “The Newtonian Legacy”:
The main character, Carl Vespers, is a particle theorist who, besides getting involved in the investigation of a mysterious death and having people trying to kill him, has to contend with more than one attractive woman throwing themselves at him, tempting him away from his long-distance girlfriend. All in all, a highly accurate portrayal of the life of a typical particle theorist. Highly recommended.
Speaking as one who knows a fair number of physicists, particle and otherwise, I can assure my nonphysicist readers that such is indeed what it’s like working in the mathematical sciences.
blizzard shuts down London! 8 February 2007
Posted by DSM in London, daily life.comments closed
Well, no. Although you’d be hard-pressed to tell from some of the whining.
There’s about three-quarters of an inch on the ground, at least near here. People are walking around with umbrellas, which is something I’d never seen before and looks strange but with no wind and very light snow then I have to admit there’s nothing actually wrong with it.
And a number of people in the department didn’t come in to work, including the guy who was going to give today’s planetary seminar. He explained that he hadn’t seen snow like this for a long time, which boggles the mind. We’re going to try videoconferencing in an hour; we’ll see how well that works.
I guess if you don’t have a car and need to take the Underground to get in, and it’s down, then you’re kind of out of luck. You could take the bus, but the city’s so large that if you’re on the wrong side I imagine that could take a couple hours and it’s a waste of time. You could accomplish more at home. And there appear to be severe delays on many lines, so that’s probably what happened.
Still feels weird, though. Honestly, in Canada, if you used snow like this as a reason for not coming in to work you wouldn’t have to worry about coming in the next day.
crack in the pavement 7 February 2007
Posted by DSM in astronomy, physics.comments closed
Yet another installment in my numerical adventures.
Had a meeting with Richard yesterday where I showed him the results of many of my test suites designed to show that my new two-timestep code was behaving pretty well. Ran some followup tests before I left for the day: he’d expressed interest in knowing exactly where it was the integrator broke down, and that sounded like a good idea.
Originally I’d planned to use a smooth transition function from the outer to the inner regions, but the analytics became a nightmare almost immediately so I’d have to have switched from the Duncan-style recursion to Chambers-style numerical integration.. and I wanted to put that off for a while. If the method worked pretty well except for transiting objects, then switching to a smooth transition would probably solve that, but if it didn’t work at all, then smoothing the transition wouldn’t help.. so it made sense to try the simple thing first.
I managed to show that the code works surprisingly well in most situations, with a handful of exceptions which I suspect are due to numerical resonances. I think this is because the forces are admittedly becoming more inaccurate on the inside but they’re also less important, and an averaged behaviour is a better approximation. However, when objects cross the boundary between inner and outer zones repeatedly — for example, an object with a respectable eccentricity with semimajor axis at the transition point — then they don’t behave so nicely. They become artificially eccentric.
I can only think of two ways to get around this. The first is to forbid objects from switching back to an outer zone timestep even if they move into the outer zone, but that’d cause problems with the way I’m handling my close encounters. The second, unfortunately, is to put in a smooth transition, which means that I have to finally finish my Chambers code. Since the boss is away for a few days, now’s the time.
On the bright side, given the subtleties of the problem, I can probably release a short paper on the technique aside from the science we’re going to generate, which is a plus..
indistinguishable but completely different 7 February 2007
Posted by DSM in Canada, politics.comments closed
The invaluable Steve Janke comments on the recent Mark Holland “there will be consequences” threats aimed Alberta’s way, riffing off an interview by Charles Adler, and captures the contemporary Liberal worldview perfectly [emphasis mine]:
Holland: Take a look at the energy that’s required to extract it from the ground, uh, even, there’s a report, now when we look at it, it’s gonna require something like 20 nuclear reactors at 600 megawatts in order to just provide the power necessary for THREE times the existing capacity.
Adler: So, would a Liberal government ban that from happening?
Holland: Well, what I think what we would do is that we would manage that resource responsibly and we would.
Notice that Mark Holland does not say a Liberal government would use less energy or more. He refuses to be pinned down on just exactly is the right amount to use. All that matters is that if Liberals were running the show, things would be reasonable and responsible, but not necessarily different.
Janke goes on to note that this the-same-but-different approach of the Liberals puts Holland in the unfortunate position of having to hold several different positions on the same policies. Those interested in Holland’s mental health should hope the Liberals don’t return to power anytime soon or he’ll have to handle not merely triplethink but quadruplethink as the laws in question become good again..
I miss Canadian politics. It’s distinctively Canadian — both boring and strangely appealing. And it’s comprehensible. Sure, it’s a little odd.. but once you get used to it, everything makes sense, from Garth Turner doing Something To Attract Notice on regular intervals to the Liberal emphasis on Lenin’s Who Whom with less concern about What. (Who? The Liberals. Whom? Everyone else.)
By comparison, British political life is more extreme and yet less varied, and very difficult to get a handle on, for this outsider at least.
this year in Jerusalem 5 February 2007
Posted by DSM in faith, sports.comments closed
And the Colts win, largely because their season-awful D shook off giving up a return for touchdown on the first play of the game and forced a half-dozen turnovers.. and Manning adjusted to the rain game better than I thought he would.
This is the first time since the Jays won back-to-back in the early 90s that my team’s won the Big Game. I’d forgotten what it felt like..
I’m especially glad for Tony Dungy, one of the classiest men in professional sports. The Lombardi trophy is the better for him having held it once again. (Backup safety long ago, which I’d completely forgotten until it was mentioned in the pregame runup.)
There’s also the neat fact that both Dungy and his friend Bears coach Lovie Smith are serious Christians, so it was X-man vs. X-man in the arena, with no lions in sight. The Fellowship of Christian Athletes has a bunch of links, including to an excellent ESPN article describing the challenges Dungy has faced including the recent death of his son.
every man has his flaws 3 February 2007
Posted by DSM in Canada, politics, sports.comments closed
The following puts me in a difficult position:
OTTAWA (CP) – Prime Minister Stephen Harper might be a big sports fan – but he’s no fan of the Super Bowl.
The prime minister offered a candid reply when asked for a prediction on Sunday’s National Football League championship game between the Chicago Bears and Indianapolis Colts. He also took a nationalist jab at the NFL. “I have to admit I’m not following it,” Harper said Friday.
“Being prime minister of Canada I can assure you I focus my exclusive football attention on the Grey Cup – which is always much more exciting.”
I can’t really see myself voting NDP, though I have many Dipper friends: reality isn’t optional, and I won’t pretend it is.
I also can’t vote Liberal, despite the fact that on many matters at least the Liberals and I live in the same universe. I’d spoil my ballot first. And then burn it.
The Bloc combine the unloveliest qualities of the Liberals and the NDP and throw in treason to boot, and I don’t live in Quebec anyhow, so they’re not an option.
Which leaves me with only one party, really: the Conservatives. And, generally speaking, the most I can accuse them of is being insufficiently conservative, and tending to inertial stupidity.
As John O’Sullivan once said in his First Law (paraphrasing): all organizations that are not explicitly right-wing become left-wing over time; and the Conservatives aren’t right-wing. They really are blandly centrist, more’s the pity. (Exercise for fellow physicist readers: deduce the First Law from basic statistical mechanics. Advanced version: generalize to include not merely right-wing politics but the Good, the Right, the True, and the Beautiful.)
So what am I to do if the Prime Minister himself proves unworthy of governing our great nation by virtue of idiotic opinions on sports? I have been heartened by his well-known hockey traditionalism and discomfort with shootouts, but this is deplorable.
Go Colts go!
