Saturday, December 26, 2009

Harper's Index for 2009

As 2009 draws to a close, so ends my first year as a resident of the UK. As such, I thought it might be a good time to look back at the year and compile a “Harper’s Index” of interesting things about this year:

Number of Airplane flights: 52
Number of Successful landings: 52
Carbon footprint: Very Bad
Number of transatlantic flights: 12
Number of transatlantic flights that were unpleasant: 12
Number of flights longer that 11 hours: 4
Number of days this year I have consumed more than three cups of coffee: 4

Estimated average number of times I have had tea per day: 2
Estimated average number of times per day I think to myself “I should go buy some better tea”: 2
Estimated number of meals I eat per week which are cooked by Somerville College: 3
Pounds I’ve gained this year: 3
Number of times I’ve eaten haggis: 1
Number of times I’ve eaten kangaroo: 1
Number of times I’ve thought, exotic food is interesting, but really I like plain food better: 2

Number of flights missed due to being late to the airport: 1
Number of holes sawed in my bed while desperately trying to recover my passport in time to make it to the airport: 1

Number of weeks I spent in Oxford this year: 30.5
Number of weeks spent traveling (including vacation): 21.5

Number of boxes moved to UK last January: 75
Number still to be unpacked: 13
Number of boxes of things I probably should have thrown out instead of moving: 13

Number of Giant Spiders in my backyard: 1
Number of Giant Spiders gone AWOL: 1

Number of weeks in the winter spent with Scarlet Fever: 1
Number of tablets of penicillin consumed: 21
Number of months in the summer with a persistent cough: 2
Number of bags of Halls Mentholyptus and Vicks Double Action Consumed: 8

Number of professional talks given: 28
Number of these I recommend for the general public: 1 (See here and here)
Number of talks which were repetitions of the same chalk-talk about Topological Phases of Matter: 12
Number of times the talk was about Topological Lattice Models and Chain-Mail: 6
Number of times I made a joke about the electric slide: 1
Number of times no one laughed at the joke about the electric slide: 1
Papers Posted on arxiv.org: 8
Number of South-Park episodes watched this year: 23
Number of South-Park episodes that were too gross even for me: 3

Number of Blog Postings this year: 98
Number of Blog Postings about Pogo: 3



Despite my physicist instincts, I know that certain important things are not easy to summarize with a single number. So here are a few more interesting opinions from the year:


Biggest advance in feeling like UK is home: I’m no longer self-conscious about the fact that everyone knows I’m a foreigner the minute I open my mouth.

Biggest little kudos to the US Government: Every time I go through passport control coming into the US, they say “welcome home”. I like that.

Biggest little kudos to the UK Government: They figure out your taxes for you.

Biggest big kudos to the UK Government: Health care works.

Stupidest thing about the UK: Lack of intelligent Plumbing

Biggest bummer: That many of the closest friends I’ve made in Oxford won’t be there next year.

Best travel discovery: At Heathrow there is always someone in duty-free waiting to give you a shot of Baileys. You can even take two or three before they get mad at you.
Wednesday, December 23, 2009

The blizzard of ’09: Another lesson in thermodynamics.

When admissions draw to a close, vacation begins. I jumped on a plane to go visit my family in the Washington DC area (Brother Alan, Sister in Law Terry, Niece Seneca and Nephew Milo). My other brother, Rob, also managed to fly in from Chicago.

Well the visit started out fun enough, but after a few hours, dire reports started appearing on all news outlets that the blizzard of the century was about to hit the area. Now DC does not get a lot of snow most years, so like London, when it does snow, they really don’t know what to do with it. In short, it shuts down the entire city.

Usually a snow day is pretty fun. You go out for short periods of time to shovel, or play in the snow. Then you come inside again to warm up. If it only lasts a few days, no big harm done. That is, unless you don’t have heat in your house. Only a few hours before the blizzard was set to hit, the heater in my brother’s house died. It was an old heater, but it certainly picked an inconvenient time to croak. Fortunately, the heater-repair-guy was able to come by before the snow started falling. Unfortunately, he was unable to do anything to help. In short, the whole thing needed to be replaced – which they would not be able to do until after the snow stopped falling.

Thermodynamics lesson: If there is no heat source inside, the temperature of the house will fall to be the same as the temperature outside.

Before the snow started, Rob and I drove out to the local home depot and filled the trunk of Terry’s little Honda civic with a stack of Duraflame logs to burn in the fireplace. We badly underestimated how much wood we would need to burn though. [Although whether we estimated correctly or not, we more or less filled the trunk of the civic. It was dumb not to try to fill it more though].

Well, even with something to burn, the large Maryland suburbia house was not really meant to be heated from the fireplace alone, so most of the house was pretty cold. As the temperature outside dipped to 20F (-7 C), the temperature inside hovered around 50F (10C). [We measured the temperature one room away from the fireplace. In other rooms, it was probably colder]. If we really burnt wood quickly, the temperature would rise only to about 55F (13C).



We all dressed really warmly. Here’s a picture of the three brothers and the Niece and Neph sitting in the room with the fireplace (Alan is on the couch with Seneca, Rob is on the chair, and that is me and Milo on the floor. Note the Oxford sweatshirt on Milo). Surprisingly Seneca and Milo didn’t seem to mind the fact that it was cold at all. They sometimes refused to even wear sweatshirts or socks insisting they weren’t cold. I have no idea what it is about children’s metabolism that makes them generate so much heat, but I was pretty cold. In that picture I was wearing two layers of pants (“trousers” in the UK. “pants” usually means underwear), three layers on top, two layers of socks, and a hat.


In this picture is our savior: Terry… and the Duraflame logs. (Note again the oxford sweatshirt).

We had a lot of fun playing inside. We ran around the house a bit to keep the blood flowing (OK, to be honest, running around the house with Milo and Seneca is on the agenda whether or not there is heat in the house). Rob and I swung Seneca and Milo around in circles until both of us had pulled all the muscles in our backs and then some.

By the middle of the next day, we were running out of wood already. The snow was not falling as hard, so we sent out a team of hearty adventurers to try to find more snow. After clearing the driveway (one of the neighbors had a snowblower) Rob and Alan took out the all-wheel drive Subaru (For those interested, here is the difference between all-wheel and 4-wheel). Not all the roads had been plowed and those that had been plowed were not very clear. Nonetheless, they made it out to a local market that had both more Duraflames and some real wood as well. They stocked up on enough to last a few more days.



This is more or less what it looked like outside at the time. The total snowfall was about 21 inches. Yeah, I know, if you are from Montreal or any other really snowy place, this is nothing. But DC is a very warm climate. That was more snow that DC usually gets in any entire year – all in one day.


Of course, the snow was pretty fun to play in too for some of us.

The next evening Rob had to go back to Chicago, and I was supposed to fly to Rochester to visit my parents. The main roads were clear by then, so it was no problem getting to BWI airport. But the airport was a zoo. There were people I talked to in the airport who had literally been there for three consecutive days trying to get home for the holidays. Many of them were military on holiday leave who had set up a virtual camp in the airport. Our planes were somewhat delayed, but at least left that day.

The next day the repair people started work on the heater. By that time, Alan and Terry had grown exhausted of living in the cold and the family drove to Terry’s Mom’s house to stay there for a while (it is not far away – if the roads are clear). With luck, in a day or two more, they can move home again!
Wednesday, December 16, 2009

Admissions

The undergraduate admissions process here is interesting. To begin with, the faculty does the admissions directly, rather than some centralized admissions office. If you apply to Oxford to “Read” physics, you are interviewed by the Physics faculty who would be teaching you, were you to be admitted. This gives the faculty a chance to choose their own mistakes.

In the UK it is a strict rule that you can only apply to Oxford OR Cambridge, not both. Given this, Oxford gets a bit over 1000 applicants for roughly 180 Physics places. Actually, that is pretty good odds for the students, as in some other subjects the ratio is much worse. Incidentally, admission here is like Early Decision in the states where it is understood that you will attend if you are accepted. A few alternates are chosen in case someone bails out, but this is pretty rare.

The students send the usual transcripts, recommendation letter (just one from their school), and short essay. They then are asked to “sit” a pretty hard entrance exam. The exam was instituted in a truly organized way only a few years ago, so the clever prep-schools are just beginning to be able to train their students for the exam. Up to this point, however, the entrance exam has been the best indicator of future success at Oxford. So the exam is now taken pretty seriously. (Perhaps once Stanley Kaplan and Princeton Review start giving courses to help people game the system on this exam, its validity as an indicator will drop).

The students who perform above a cutoff on the exam are “summoned” for interviews (this does not involve flue-powder). Those that do not make the cutoff are “de-summoned”. In a few cases, a student may be “rescued” from below the cutoff for one reason or another – for example, if their school does not even teach physics and they had to learn everything on their own. If you score way up near the top on the entrance exam (top 50 or so) you are virtually guaranteed a place unless you do so badly on the interview that you are suspected of cheating on your exam. In all, roughly half the students are summoned for interviews. So that means roughly 2.5 students will be interviewed for one place.

When the students are summoned for interviews, they are asked to come to Oxford for several days – during which they stay in the dorms and mostly seem to roam around and get nervous about their interviews. During that time they are given at least three interviews. Interviews are typically done in teams of at least two interviewers to one student. Whichever college is the student’s first choice college interviews the student twice (two teams of two interviewers), and their second choice college interviews them once. Sometimes a student declares a first choice college, but that college has too many applicants so the student is assigned a new first choice college. If you are a phys/phil (physics and philosophy) candidate you are interviewed these three times by physicists and then at least twice by philosophers as well. Some of the overseas candidates are interviewed by telephone, and one has to assume that these interviews have bigger error bars. We have a fair number of overseas applicants, but I'm surprised we do not have more from the US. (Even including travel costs, Oxford is still less expensive than most elite US colleges I think).

Each interview results in a grade from 1 to 10. All of the interview scores are uploaded to a central database, which all the faculty can examine. All of the student's information (including grades, tests, interviews, etc etc) are posted and also amalgamated into one overall score and everything is listed in a systematic and organized way. Each college is listed along with how many slots they need to fill (usually 6 or 7 per each of about 30 colleges) and all the data about all the students they interviewed is listed too. (Hogwarts college is also listed in this file – I’m not making this up, I think it represents stray unaffiliated interviews, unaffiliated students, or something like that). Once all this data is posted, then the drafting and horse-trading begins.

If a student has an amalgamated score in the top 100, they are essentially assured a place – and almost always in the college they designate as their first choice. Even if their first choice college does not want to take a high scoring student for some reason, these students will be snapped up by the second choice college or by other colleges who did not get enough good applicants. Almost all of the arguing and finagling is to allocate the last 80 places in the class. Essentially we have to pick 80 students of roughly the next 200 highest scorers at this point (and defend the decisions).

If a student scores worse than 300th, they are almost certain to be rejected. In a few rare cases, a student will mathematically land worse than 300th, but will be rescued because of extenuating circumstances – like if they come from a particularly poor school, or difficult family situation, and they had to work like crazy even just to get this far (which is often a good indicator that they will still be able to do well by continuing to work like crazy). In these cases, the colleges that decide to take students who score lower, must stand up and make the case of why they are not taking better scoring students… and sometimes they are even requested to report years later on the progress of such rescued students to reaffirm that this philosophy of breaking the rules is actually a good one.

This year I won’t be taking part in the horse trading meeting (the other physics fellow from Somerville is in charge this year… I’ll get my chance next year). The meeting sounds a bit like the NFL draft, where everything happens in real time and every decision is publicly announced with great fanfare – and objections may be raised at any time and the drafting team must defend its decision. The college representatives (the faculty) have several objectives --- both to draft a good "team" for their own college, but also to make sure that any student they think is worthy is taken by some college, even if their own particular college does not have a place for them.

This year I think Somerville will do very well in the draft. While, not having any super-super-stars, a number of strong candidates listed Somerville as their first choices – and we will be very happy to have them. We need to recruit about 6 students and we have most of them nailed down before the draft starts. I’m optimistic that this will be a reasonably good class!
Saturday, December 12, 2009

Why The Principal Knows Everything

I’m always the last to figure things out. But the clues were all around me:

Fact 1: Dame Fiona, the principal of Somerville college Oxford, seems to know everything that goes on within college. I always attributed this to her particularly acute perception –- on account of the fact that she was trained as a Psychiatrist.

Fact 2: Dame Fiona’s cat, Pogo, freely wanders the entire college, frequently unobserved. Yesterday he was sitting amongst the high school students as they waited for their admissions interviews.



Fact 3: I have never seen Fiona and Pogo in the same place at the same time... except in this very famous painting of the two of them that hangs in the great Hall.

Yes, now it is obvious: Pogo is Fiona’s alter-ego. With appropriate credit to J. K. Rowling, Fiona is obviously an Animagus, akin to one of my favorite characters Minerva McGonagall who also turns into a cat, and who also is the head of a house… coincindence? Hmmmm...

The painting is painted by Susannah Fiennes, who is the cousin of Ralph Fiennes, who plays Lord Voldemort in the films. Another coincidence? Hmmm... See correction in comments section.

[Photo Credit: Christiane Riedinger].
What is physics? I mean, what is it all about? What is the big uber-goal that we are all working for? What are the really important directions of research these days?

If you ask a physicist any one of these questions, you will inevitably get the same kind answer. Every physicist will tell you “What I work on is really important and interesting. What I do is what physics is about.” (Here “I” means whoever you ask, not “Steve Simon”). And I think most physicists passionately believe this. If they didn’t believe it, they probably would have (or should have) switched fields long ago to work on what they think is truly important.

Just for example, if you ask “is physics an experimental science?” chances are if you ask an experimentalist they will say “Of course.” If you ask a string theorist, they might say “Er… not necessarily.”

I think this diversity of views of physics is a good thing. The only thing, we really all share, is the underlying belief (perhaps faith) that the world around us can somehow be understood. However, sometimes diversity of views causes some real problems. Obviously dividing up the limited funding pie is a seriously sore point for many people.

“Why should *THEY* get so much funding when what *I* do is so much more important and interesting.”

“Do we really need to hire another physicist who does X when Y is so exciting these days.”

Or conversely

“That stuff isn’t even physics! Why would we pay to have *that* in our department”

Here at Oxford this diversity of opinion rears its head in some interesting places. One point of conflict (that seems less prevalent in the states) is over the undergraduate syllabus. Here in the UK (indeed in much of the non-US world) the undergraduate syllabus is extremely constrained. This is quite a change from my undergraduate experience (Brown University) – which required only obtaining 28 passing grades for graduation, and had no further detailed requirements: every choice of what to study was left completely to the student. In Oxford, the students follow a very rigid path. [ There are obvious advantages to each system – to be discussed another time.]

So it seems that over here someone is always saying what a travesty it is that a student with an Oxford physics degree might graduate without any exposure to X, Y or Z. Typically the person stating this is someone who has particular interest in X, Y, or Z. Further, getting X,Y,Z into the curriculum boosts the status of those researchers who study X,Y, and Z in the department – as there will always be a need, thereafter, for people to teach the subject.

But do undergrads really need X,Y,Z? How much does it even matter what they learn? Is a college degree about learning a particular topic, or about learning how to learn – about stretching you brain on anything really hard.

I think both answers are valid, although I do have a bias. If you want to guess my bias… here is a hint: For the record, here is a list of courses that I did NOT have as an undergrad:

Statistical Mechanics
Thermodynamics
Solid State Physics
Electricity and Magnetism
(beyond the level of Purcell’s introductory book)
General Relativity
Astrophysics or Cosmology
Advanced/Relativistic Quantum Mechanics
Field Theory
Fluid Dynamics
Optics
Advanced Laboratory

[yes, I did realize upon graduation that I was woefully unprepared for grad school, so I finagled to take some extra courses for a year to make up some of the difference].
Tuesday, December 1, 2009

His Dark Environment

The winter here gets very dark. This is not surprising considering how far north we are. Despite our relatively mild winters (courtesy of the Gulf Stream) we are far north of even Quebec City.

The shortest day of the year, the winter solstice, December 21st --- is a date celebrated in one way or another by most cultures on earth. On this day, London only gets 7 hours and 50 minutes of sunlight – substantially less than New York which gets 9 hours 15 minutes. On the other hand, if you happen to live in Oslo, you only get 5 hours 53, and if you live in Svalbard you won’t see the sun at all from the end of October til mid February.

However, surprisingly, the solistice is not the day when the sun sets the earliest, or rises the latest. In New York, the earliest sunset is actually December 8th and the latest sunrise is January 4th. As you get further north, these two dates get closer together: Here in London, the earliest sunset is December 12th and the latest sunrise is December 29th.

At one point in graduate school I remember pondering the geometry of why this happens --- which has to do mainly with the angle of the earth with respect to its orbital plane (if I remember correctly). I think it was my friend Dave Morin who managed to figure it out --- not surprisingly he just finished writing a classical mechanics textbook with a ton of really hard problems in it.
Saturday, November 28, 2009

Where is Shelob?

Earlier in the year I blogged about S.O.U.S. (Spiders of Unusual Size). One of these little beasts had made her home in my backyard and I decided to give her a rather wide berth. Particularly since I was away so much of the summer, it seemed reasonable that she could have reign of the backyard while I was gone. Well, returning home for the beginning of noughth week, I discovered that she had disappeared – vanished without a trace. I joked that we had made a deal, I bought her plane tickets to florida for the winter, and in return she spun a web with the words “Some Physicist” (*). However, what I really suspected was that she had just come to the end of her life cycle (which for some spiders is not very long). Particularly in cold climates, spider life cycle tends to be yearly and it I figured it was a good bet that Shelob had croaked.

Alas, I fear this may not be the case. Over lunch with Dame Carol Jordan, the discussion randomly turned to the S.O.U.S. “Oh, yes”. She said. “I think that type of garden spider hibernates for the winter and comes back out in the spring… impressive little things aren’t they?”.

I wish I hadn’t asked. Remind me to not go out in my backyard for the next year or two.

(*) Joke credit goes to Nuntiya Kakanantadilok
Us nerds know how to party.

My friend Christiane decided that for her birthday she would throw herself a star-trek themed party. You might expect this to be a complete nerd-fest (ok, maybe it was) but it was really fun!

Here is a picture of Christiane dressed as 7 of 9.


And here is a picture of the actual 7 of 9.. not bad huh?



Then we had Christiane's boyfriend Luke dressed as Riker (left) and Dina dressed as Betazoid Deanna Troi (right). Dr. Justin is in the middle there appropriately dressed as a medical officer. Compare to the original Riker and Troi:

Random vulcan star trek officers included Christiane's mother and sister:

Note the full life-sized picture of 7of9 in the background. Also note the flag of the united federation of planets. Way in the upper left of that photo you can also see part of some random star-trek weapon hanging on the wall. Probably Klingon.

And one photo of the general crowd. Darcy in the foreground has some serious vulcan ears... or maybe they are elf ears she is just trying out in advance of the next party --- I'm hoping for a lord of the rings themed party coming up soon.

Dancing went on til 2am. Not a bad party.
Wednesday, November 11, 2009

Too Cliché: The great discovery of Ogg.

.. and while I am on the subject of thermodynamics..

Once upon a time there was a very clever caveman named Ogg. Ogg made the remarkable discovery that hot plus cold equals warm. Although this knowledge has been passed from generation to generation, somehow, the memo did not reach British plumbers.

Of all the complaints Americans have about the UK, one of the most cliché, and yet most valid, is the complete stupidity of the plumbing. The Brits absolutely insist on having two taps for water: one that delivers hot water and one that delivers cold – and never the twain shall meet. So when you wash your hands, you have the choice of water that is scalding, or water that is freezing. Americans inevitably turn them both on then rapidly pass their hands under each one in quick succession to create the illusion of warm water while trying not to burn themselves. (Kirill Shtengel likes to joke that the British shower has a hot shower head and a cold shower head and you are supposed to jump back and forth between the two).

I mean, how hard is it really to plumb the two taps together so you can make warm water from hot and cold?

Yes, I understand the intention is that you are supposed to fill a basin with the combination of the two, and then you are supposed to wash your hands in the basin. But, for example, in a public restroom, you usually don’t have a plug for the basin, and even if you did, you wouldn’t want to actually touch water that had touched the basin anyway.

In my house, there are three sets of faucets. The kitchen sink, the bathroom sink, and the tub. Of the three, the only one which is 20th century in its plumbing is the tub – which conveniently is the only one of the three where it really doesn’t matter.
Sunday, November 8, 2009

Thermodynamics

The weather is turning chilly here in Oxford. Like clockwork, the heat and hot water failed in my apartment last week. I became painfully aware of an important principle of thermodynamics: When it is cold out, if you don’t have heat, you get pretty cold too.

Anyway, after a few days of poking at the boiler, I narrowed the problem down to a problem with the pilot light. I tried relighting it, but even after a dozen attempts or so (and a few more cold nights), still no luck.

My last resort before calling a professional was to consult the oracle of google. Typing in “flamingo 40 boiler pilot light problem” came up with a number of discussions of exactly this issue. It turns out there is some “Overheat Themostat Reset Button” hidden in the device. If it gets tripped you have to reset it before the pilot will light again.

As a physicist I've always been a big fan of thermodynamics. Reading about thermo makes me generally happy. But I think watching the heat come back on after multiple cold nights made me even happier than reading Enrico Fermi's great lectures on thermo.
Monday, November 2, 2009

2009 Concert Tour

Many rock bands go on tour and give the same show night after night. Typically they sell t-shirts listing all of the locations and dates where they performed. This is what I feel like with the colloquium talk I’ve been giving this year. I constructed the talk for KITP Santa Barbara last spring (See here. On the web here) and it went over so well that I decided to do a few repeats. Soon, word got around that it is a pretty fun talk and all of a sudden, I’m doing repeat performances all over.

Here is the list just for October and November:

Friday October 2nd NUIM Maynooth Ireland
Thursday October 8th Univeristy of Warwick, UK
Friday October 23rd, University of Exeter, UK
Friday October 30th, University of Saint Andrews, Scotland
Friday November 6th, University of Leiden, Netherlands
Wednesday November 18th, Royal Holloway University, London ,UK
Wednesday November 25th,University of Utrecht, Netherlands

By the end of the term, I suspect I will be rather sick of this talk. Maybe I’ll sell t-shirts* (or veggie burritos).

*Credit: the idea of making a concert t-shirt is from Susanne Viefers.
Sunday, November 1, 2009

Andy, Andrew, and Saint Andrews

My two friends Andy McKenzie and Andrew Green used to be the only two people I knew in the Physics department at the University of Saint Andrews. I postulated that your name had to be Andrew to work there. This postulate was eventually disproven when they hired Chris Hooley.

This week I visited Saint Andrews for only a day, and had a terrific time while there. (Sadly, Chris, who is endlessly entertaining (See here), was not around during my visit).

When I arrived in Saint Andrews, I met up with Andrew Green for a pint of Deuchers (which is a very fine Scottish beer) and a sushi dinner. Then we went to a bar where there was a jazz jam session. Andrew is a very accomplished jazz trombonist, and over the years (I hesitate to say how many years we have been friends now) we have frequently talked about our common interest in jazz. I haven’t played in a quite a few years; and I believe somewhere along the line Andrew also fell out of practice for a bit, but unlike me, he did manage to start up again (with some effort) and now plays quite well. I was really looking forward to hearing him play for the first time. He even suggested I bring my horn, but I couldn’t bear to play in public without at least a few months of woodshedding to get the chops back in order … maybe this will be a project for the future. Anyway, the Saint Andrews jam session seemed like a very nice group of musicians. People subbed in and out very generously, and nicely accepted players of all levels. Many of the players were pretty good, and some were extremely good. One or two were less than good (to put it generously), but no one seemed to mind much. Rather than making me cringe, it made me feel that I should have jumped in and played --- chops or no. The bar was crowded and most people were only half listening anyway, so the occasional painful moments passed without notice.

Andrew did a super “Stolen Moments” (To quote him, “That tune works really well on trombone”). His playing was extremely clean (Even some very good trombonists fall short on this score), and his improvisation on this tune was very smooth. I was suitably impressed. The rhythm section was led by an ancient, and rather portly, pianist who was great. The drums and bass were also quite good. The guitarist -- a retired GP who looked like he was about to keel over at any moment -- also managed to hold his own. Andrew opted out of most of the tunes of the evening to give others a chance to play.

I’m sure the jam session would have gone late into the evening, but for the fact that by decree of the neighbors music must stop in that bar at 11:30. Perhaps this was just as well, as I had had a long day already – having been awake way too early to give all my tutorials in the morning at Oxford before heading to Heathrow.

**

The next morning, after my colloquium (which went very well), I chatted physics with three very interesting sets of people for the rest of the day:

First, Andrew Green – I took the opportunity to tell him all about this topic which I am pretty excited about these days. He gave last week’s condensed matter theory forum talk at Oxford (which was excellent), so I had already heard recently about his work.

Second, Ulf Leonhardt: I had never met him before, but he seems to be doing some really interesting stuff. Among other things, he was one of the guys who developed the recently publicized idea of the invisibility cloak (yes,that is for real).

Third, Andy McKenzie and his research group. Andy is a terrific experimentalist who studies many interesting exotic materials systems – including Sr2RuO4 which is one of the materials that “topological” people like me are most interested in these days.

I wish I had had more time to chat with everyone – but soon enough it was time to rush back to the airport. Maybe I’ll go back up there for another visit soon.

PS: This is my 100th blog posting!
Friday, October 30, 2009

I am going to gain so much weight

A few night’s back, high-table dinner was a terrific leg of lamb. Fist course was a shrimp salad, and dessert was a chocolate and beet root cake (sounds strange but it was actually wonderful). As if that was not enough to keep me fed, the cake was served with clotted cream – which, when combined with the cake, is delicious! Once I turn that corner and start eating clotted cream… it is only a matter of time.
Thursday, October 29, 2009

The Squalid State

This posting is not about the status of my flat (no comment as to whether that would be an appropriate title).

“Squalid State” is the derogatory term used to refer to the field of “Solid State” physics by other physicists, and sometimes with good reason. The field is full of people studying what appears to be the boring minutia of particular physical materials: why this impurity increases specific heat and that impurity reduces it – and so forth. This entire field of study looked so horrid to me when I was an undergrad that I absolutely refused to even consider taking a solid state physics course.

It is rather ironic then that I became a solid state physicist – or, more properly, a “condensed matter” physicist who spends a lot of time thinking about solid state. So why am I now excited about the field whereas once-upon-a-time I thought the whole endeavor was dismal? Well, I now realize that some of the most exciting physics out there is in condensed matter systems, that the diversity of condensed matter is unrivaled in any other field, that many of the deepest ideas can be tested and explored best in condensed matter systems, not to mention the importance of potential applications in this field. Unfortunately, these exciting features are extremely well hidden in introductory solid state physics courses --- almost as if by design.

This year the physics department at Oxford has decided to revamp its third year syllabus. Everyone agreed that the previous third year undergrad program was not working and that we would all benefit from trying something new. I volunteered to develop the solid state physics course for a maiden voyage in 2010-2011, when I will teach this to 180 student, more or less. I view myself as the ideal person to teach this precisely because I thought it was so boring. My job will be to make it non-awful, to somehow bring out the exciting part of the field rather than the dismal part.

However, to some extent I am trying to do this with one hand tied behind my back. The IOP (british Institute of Physics) mandates that certain topics MUST be taught in an undergraduate syllabus. Further, my colleagues will not stand for me eliminating certain other topics. Finally, the total number of lectures cannot exceed 22. Despite these rather serious boundary conditions, I still think that I can put together a very nice course – and this is what I’ve been working on for the past few weeks, and will continue to work on for the next year.

So, to all the physicists reading this: Did anyone have a good solid state physics course? If so, why did you like it, who taught it, what was covered, what book did you use?
Thursday, October 8, 2009

Noughth Week

Last week ended my summer of constant travel and I returned to Oxford for “noughth week”. To understand this nomenclature one needs two pieces of information:

First, the weeks of the term are numbered 1-8 (Yes, the terms are only 8 weeks long, making them officially insanely short). No one at Oxford ever uses real calendar dates – instead they will just say “our next meeting is Monday of 5th week” or something of that sort. If you make the mistake of asking “what are you doing on November 3rd?” a person will likely ask “which week is that?” This system does actually make some sense because you can have meetings that occur perpetually on, say, Friday of 1st week (as the Physics Theory Sub-Department meeting does) independent of the term or the year, which is then somehow immune from the fickle fluctuations of the Gregorian calendar.

The second piece of crucial information is that “noughth” means “zeroth” (as in “all for nought”).

With those key facts it should be clear that “noughth week” is the week before classes actually start at Oxford. During this week in Michaelmas term (fall term) the new first year undergraduate students (“Freshers” over here rather than “Freshmen” or “Frosh”) arrive, and the 2nd-4th year students return, hopefully more rested than I am, from their summer breaks.

Over the course of noughth week, things accelerate extremely quickly. Since the terms are so insanely short, once you are in-term, everything is a sprint. The students move in by about Wednesday of noughth week, and by Friday all organizational meetings are done so that by Monday of 1st week, the term is going full speed.

Perhaps the most important event of the week is meeting the new Freshers, which mostly happens at an event known as Fresher’s Dinner. This is a formal dinner in the Great Hall where, very unusually, the Faculty sits at the tables with the students (usually the faculty sits at High Table). As one of my colleagues warned me “Depending your students, this dinner can either be really fun and interesting, or a socially difficult Marathon of trying to think up small talk”. Fortunately, my incoming students this year were a lot of fun to chat with.

Oh, and the Somerville chef decided to serve Kangaroo meat (there was also a vegetarian option). And of course there is a lot of wine at dinner. The drinking age is 18 in this country – so this is to be expected for a formal dinner.

This year’s crop of new Physics students at Somerville consists of four boys and two girls, plus one Physics-Philosophy hybrid, also a girl, making the gender mix pretty close to 50/50. While there are a few girls in the upper classes, it still is a bit unusual to have such a high fraction of girls in the Physics group. (My second year students, for example, are six boys and no girls). Perhaps this is just gender balance finally coming to physics, or perhaps it is an anomaly (or more likely a bit of both).

At any rate, now that the term is starting, my life is about to become completely insane for the next eight weeks. Forgive me if I am a bit sparse on the blog postings.

Oh, and with history repeating itself, at the beginning of noughth week, I had the flu.
My grandfather was a bookie – a guy who professionally handles bets. Although a good bookie never needs to risk much of his own money (since his bets are well balanced with just a bit of a margin for profit) most bookies do know what a good bet is and what a bad bet is.

Apparently I have no idea what a good bet is – even when I know a topic extremely well. My predictions for the Nobel Prize in Physics this year were way off*. Even listing everyone I could think of who was in the running, I didn’t even get close. The winners were not even on my radar screen. This is particularly embarrassing since two of the three winners were old Bell Labs guys and I certainly knew very well of their work, and of its importance [ although I never met either one of them since even the younger of the two retired from Bell a decade before I ever arrived ].

The two guys at Bell, Smith and Boyle, are credited with inventing the CCD (Charge Coupled Device). That is the little semiconductor gizmo that turns an optical picture into a stream of electrons which then can be turned into a digital computer file. There’s a CCD in every digital camera. The other guy, Kao, who shared the Nobel with them, developed the fiber optic, which comprises the famous “series of tubes” which carry information through the internet. Bits of information are turned into photons that run down glass fibers called optical fibers.

The prize this year was perhaps an unusual one – it is clearly technology rather than physics, but it is important technology. There has been some grousing around the internet (for example, here) that this prize was not deserving because it is just engineering. (Here I’m repeating here a comment that I posted on Doug’s blog here) The key question is what the Nobel prize should be about --- what the Nobel prize "brand" should mean. There are certainly plenty of important technology/physics advances that could potentially be recognized --- and the original intent of Nobel’s will certainly gave this latitude. It also said that the discovery should be made within the previous year --- a requirement which has been duly ignored ever since ---- which shows mainly that the Nobel committee can do whatever they want to do to promote the "brand" as they see fit. However, by far, MOST of the prizes have been for "fundamental" physics advances, and not for technology advances, which sets a precedent for what the committee thinks it is supposed to be about and this prize does not look so consistent with that interpretation. (The integrated circuit prize was another recent prize for technology --- although I think that this prize was perhaps more agreed upon as being a universal game changer that needed to be recognized).

*I did make the right prediction for the Nobel Prize in Physiology and Medicine, but almost everyone seemed to know that one in advance.

** Added: Obama's Nobel: Yes, I was pretty surprised by this one too. Many people say he hasn't earned it yet, but if you read the explanation given by the committee, it makes sense. I like it.
Tuesday, September 29, 2009

The return of Delsey?

The online web BMI lost luggage system now reads "Item Located, pending confirmation". Should I get my hopes up?

Wednesday Sept 30: BMI is expecting my luggage to arrive at Heathrow from Paris today. I'm supposed to check back later today. It has only been twelve days that I've been living without my travel iron and my Snoopy t-shirt, I suppose a few more hours won't hurt.

Thursday Oct 1: Well, they didn't get it yesterday afternoon, and now since it is officially more than 12 days the BMI baggage tracing system is no longer tracking it and now it becomes responsibility of the central BMI baggage service -- who does not have a web site and refuses to answer their phone. ARGGG!

Friday Oct 2: Now I'm told that Air France has delivered the bag to my home in Oxford. This is rather surprising, as there is no one at my home to accept it -- and the mail slot is certainly too small.

Friday Afternoon Oct 2: I'm starting to believe that I might actually get Delsey back. Air France claims to have given the bag to a courier company who is tasked in getting it back to me once I return to the UK. Perhaps this story might have a happy ending after all.

Sunday 12:15 PM Oct 4. Oxford. I have been reunited with Delsey. It only took 16 days.
Sunday, September 27, 2009

Nobel-Bets 2009

Well, it is that time of year again – the time when some really smart people start losing sleep worrying about whether they will get the Nobel prize. For the literature prize the official betting odds are listed here. The favorite is Amos Oz, but Bob Dylan is a 25:1 long shot on this list.

For the physics prize, each year, I try to make a few predictions for who will win. Last year’s incorrect prediction is posted on my blog here (Egad, that means I’ve been blogging for a whole year now!). This year I decided to do a bit more homework before making my prediction. While neutrino mass (my prediction from last year) still seems to me to be pretty important, after scanning the web, it seems to me that almost no one thinks that this is a contender. I suppose, like for the Oscars, the opinions of the masses may be important, so this year I am switching my bet to

Yakir Aharanov and Michael Berry

These two studied what are known as “Geometric Phases” in physics. (For the experts, yes, you can think of the Aharanov Bohm phase as being geometric, although you have to expand your picture of geometry a bit). Perhaps the simplest example of an interesting geometric phase is the strange quantum mechanical fact that when you rotate an electron around in a circle by 360 degrees you do not get back to where you started.

The Reuter’s web site gives Aharanov and Berry support from 19% of those polled. (Several other blogs here and here and here and here agree that this is a good bet).

However, according to the Reuters shortlist, the frontrunners for the prize should be recognized for discovering forms of carbon. Reuters proposes Geim and Novoselov (22%) for the discovery of graphene (carbon sheets) and Ijima (14%) narrowly behind for the discovery of nanotubes (carbon sheets rolled up into a tube). Not that I am opposed to carbon but…

I will remind everyone that Buckyballs, yet another form of Carbon, already won the Nobel prize recently – but in chemistry, not physics. I will also remind everyone that not every molecule made of carbon deserves an immediate Nobel prize. I know that the Carbonists have been lobbying hard, and admittedly both nanotubes and graphene are pretty cool. But I don’t think they are so overwhelmingly cool that they need a Nobel prize just yet. And if the lessons of Buckyballs are anything to learn from, we should expect that the hype will far outweigh the actual usefulness of, or interest in, the stuff in the long run.

A few other people who appear to be on many of the shortlists are Cirac and Zoller (too early in my mind, but maybe sometime soon), and Peter Higgs (not until the elusive Higgs boson is actually discovered). Daniel Kleppner is another person frequently mentioned. Some people have proposed John Pendry for metamaterials and the famous cloaking device (while cool, i think this is far from Nobel material). Also the discovery of the top quark is still waiting for a prize and of course my prior mention of neutrino mass I still think is deserving. I'd also like people to think about some of the dark-horse candidates: Thouless, Halperin (my PhD advisor, I'm biased), and Haldane, are some of the people from my community who could potentially be in the running.

Anyway, we will find out within a few days now.

In other Nobel prediction news:

In Physiology and Medicine, one of the names very high on the Reuters list is Seiji Ogawa. He’s an old Bell labs guy, who invented functional MRI (fMRI) - the MRI machines that can see brain activity. For a brief moment, I think he was listed as being a consultant and I was listed as his boss at Bell labs, although in truth by that time he was listed on our roster for publicity only... and he never showed up any more – I suspect he would not recognize me if I bit him (and I have no intention of biting him, whether or not he wins the prize).

Other contenders in Physiology: Telomerase seems to be the front-runner, with stem-cells another good bet.
Since this year marks the 200th birthday of the composer Felix Mendelssohn, it seems only fitting to give him a chance to compete head to head with the great master – the heavyweight world champion, Johann Sebastian Bach.

The concert last Thursday evening, part of a festival called “pipeworks”, juxtaposed Mendelssohn organ and choral pieces with Bach organ and choral pieces. One is supposed to hear how heavily Bach influenced Mendelssohn, but I like to think of it as a competition where we have given the challenger a chance to win the championship belt.

The competition concert started with a Bach organ Prelude and Fugue (C major, BWV 545). While this is a great piece, the delivery left something to be desired. The pipes of the organ that were used in this performance sounded a bit too much like a Nintendo Game-Boy. So while this should have been spectacular, instead it left just enough room for the Mendelssohn fans to think that Bach could be defeated that evening. But before getting too cocky, these fans were smacked down by Bach’s amazing Double Chorus "Komm, Jesu komm” (BWV 229) which was excellently performed and set an extremely high bar for the challenger to try to match. (Here's a pretty good recording from the 90's).

The next section of the evening was perhaps the most interesting: six short organ pieces by Bach (BWV 599,606,614,618,621,630) from the Orgelbuchlein alternately interspersed with the six "Spruche” (Op 79) by Mendelssohn for choir. While the Mendelssohn choir pieces were also excellent, these organ pieces are masterworks and are more varied and modern than you might expect from Bach. The organist did not repeat the mistakes of the Prelude and Fugue and generally gave an excellent showing. The final BWV 630 was in classic Bach style and was perfectly performed. (Here is one you tube and another of the piece)

At the two thirds mark, Bach still held a strong lead. But the closing innings would belong to Mendelssohn.

The final part of the program gave the challenger his chance to shine: A performance of his Double Chorus Psalm 2 ``Warum toben die Heiden,” followed by his organ sonata in C minor (Op 65 number 2). While these are both very nice, they were still clearly outshone by the earlier Bach. When the competition concert was over, Bach still remained the champion, but it was a solid and respectable effort from Mendelssohn.

My colleague here at Maynooth, Joost Slingerland, and his wife Theresa, both sing with the Mornington singers who performed the choral part of this event. Kudos to them, the entire choir, and the organists. And Kudos to Mendelsson and Bach!

250 years of Good Beer

September 24th of this year marked the 250th anniversary of the day when Arthur Guinness founded his beer-making factory. For an annual rent of 45£, he bought a 9000 year lease on the land his factory is built on. Nothing like planning ahead. Considering global warming, all of Dublin might be underwater before the lease comes up for renewal.

The Guinness Corporation has very cleverly invented a holiday which they call “Arthur’s Day” to celebrate the founding of their famous product which should be considered more of a mix between chocolate milk and oatmeal than a real beer. On September 24th at 17:59 (5:59pm) everyone was supposed to go to the Pub and drink a Guinness (Get it?, 250 years ago it was the year 1759). Around Dublin, Guinness also funded a whole lot of festivities – cool bands and the like at multiple locations.

As it turned out I happened to be in downtown Ireland in the late afternoon on Arthur’s day (I had just given a talk at Dublin Institute for Advanced Studies) so I stopped into my favorite little pub just before 6pm. It was standing room only, and the bartender was pouring Guinness full speed from six taps in parallel. I grabbed a pint myself and joined the crowd in watching the official countdown to 17:59 on TV. This seemed a bit too much like New Years –- except no one knew quite what to say when the clock hit 17:59. “Happy… er… Pint?”. Strangely, the event on TV was celebrated by a performance of Tom Jones singing “It’s not unusual”. This can only be described as surreal. I’m sure Arthur Guinness is rolling over in his grave.

Anyway, after finishing off my pint, I left and started walking around the city. Every single pub (and there are very many) was overflowing into the street, and every person was drinking Guinness. What an amazing marketing coup.

I wandered around Dublin observing all the people drinking Guinness (observing also that the new dress code for young women in this town involves insanely high heels which appear impossible to walk on – but this is another story). But instead of going into one of these pubs, instead I went across town to go to…


(To be continued next blog posting)
Saturday, September 26, 2009

The No Spin Zone

Have you ever gone swimming with your jeans on? Jeans can absorb so much water that you can wring them for about an hour before they become classified as only “wet” as compared to “sopping wet” ? Well, that is what my jeans were like when I took them out of the laundry machine when it refused to run the spin cycle here at the seminary. The young Irish seminarian who was in the laundry room washing his frock (literally) told me “Aye, I'd pray hard before using that machine... the devil himself is inside 'er”.

Maybe this is the moment when I am supposed to find religion. Instead, I have wet laundry hanging inside my room.
Thursday, September 24, 2009

Me and The Priests

In 1795 the British government decided to build a beautiful Catholic seminary in Ireland to train priests. If you know much about Irish history, you will realize how strange this sounds: the Brits hated the Catholics, and oppressed them for hundreds of years. Why on earth would they go out of the way to build a nice seminary for them?

Well, this is a classic (and rather brilliant) case of keeping your friends close and your enemies closer. Since there were no seminaries in Ireland, the Irish typically went to France for their religious education. Long about that time, the French were having this thing called a revolution where they were cutting off people’s heads – particularly those in the ruling class. The Brits were justifiably afraid of having folks come back to Ireland with ideas of revolution, so they decided to keep their enemies closer by building a nice seminary in Ireland to keep them at home. In this way St. Patrick’s College was established in Maynooth Ireland, just outside of Dublin, and it has been operating as a seminary, training priests, ever since.

After a few years they decided to expand the seminary to become a broader university and the location eventually became what is now the National University of Ireland at Maynooth. By the auspices of Science Foundation of Ireland, I am officially a visiting professor at NUIMaynooth for some number of weeks per years in 2009 and 2010 (This is a complex arrangement that we started negotiating back when I was still at Bell, and it is officially so confusing that I have no idea of any of the details by this time).

At any rate, for this particular visit to Maynooth, all of the low budget “regular” rooms have been booked, so I’ve been staying in the guest rooms of the seminary. I was told that there would be a conference of Bishops during my stay, and that I would have to be extra quiet so as not to disturb them. So every morning at 7 am, I make sure to crank the Led Zepplin at 9 on my stereo instead of 10.



Here is a good picture of the building where I’m staying. It has 20 foot high ceilings everywhere (that is close to 7 meters, for the international audience) and the hallways are close to the same width as height. You could march a team of clydesdales down the hall in parallel without them feeling at all cramped. I’m not sure why the monks in 1795 decided they needed to march horses down the hallway in parallel, but apparently they did. You might even be able to march an elephant down the hall if you tried.

As you can see in the photo, the windows are extremely tall – probably 15 feet high. The room I’m staying in is sparsely decorated. Just a large bed and a tiny table, and lots of extra (wooden) floor space – which I could use to play soccer, I suppose.

Standing at the position where the above photo was taken, if you turn around 180 degrees, you see the main building of the seminary in this picture --- which also houses such crucial things as the student cafeteria in the great Hall (which I would have once called Harry-potter-esque, although now I probably would just call it Oxford-esque).


I’m still entertained that there is a strict division in the cafeteria –-- one section is roped off and labeled “reserved for seminarians.” Perhaps they are afraid of the corrupting influence of evil people like me (I do have horns, you know).

Anyway, returning to the photos above, there is a legend that it is bad luck for undergraduates to walk down the path in the center of these pictures. The source of this legend is thought to be that faculty members would sit at the sides of this path and think deep thoughts when the weather was nice, and whenever undergraduates bothered them by walking down the path, the faculty got upset and made the exams just a bit more difficult.

Although the area around the university is pretty, most of it is not ancient like these two pictures. The campus is split into a north and south half divided by busy Kilcock road. There is a walking bridge over this road, with signs indicating that one should not cycle over the bridge. Every one of these signs has succumbed to graffiti by this time. My favorite one now says "No Cycling, Sasquatch". Must be the seminarians with the sense of humor.
Sunday, September 20, 2009

My Delsey Suitcase

I bought my rolling Delsey suitcase almost a decade ago. It is one of those rolling small black bags that you see in airports all the time. When I bought it, it was the largest suitcase size that was still small enough to fit in the carry-on – which made it the ideal suitcase. However, sometime in the intervening years, the airlines slightly decreased the size of a bag that you are allowed to carry-on (even though the suitcase will certainly fit, they now tell me it is too large almost always), and now my Delsey bag is instead the smallest suitcase that you are not allowed to carry-on to an airplane. As a result my ideal suitcase is now a bit less than ideal. But I haven’t gotten around to replacing it yet.

Last week, I was in Ireland, attending this conference, and I am staying Ireland again this week, but since I had to be in Cambridge to sit on a thesis committee on Monday, I went home to Oxford for the weekend. Arriving at Dublin airport, and checking my Delsey suitcase at the British Midland International airline (BMI) counter, I happened to comment to my friend Gunnar Moller that his carry-on suitcase was the ideal size, whereas mine is now not ideal. I think “not-ideal” is a bit of an understatement. Somehow in the course of the one hour direct flight from Dublin to London, BMI managed to lose track of my suitcase. Two days later, it still has not turned up. While I’m not crushed to have lost the Delsey (which, admittedly, was no longer ideal), I’m quite annoyed to have lost the entire contents of the suitcase. The people at BMI tell me that if it doesn’t show up within 5 days, they file it as lost and I have to negotiate with their luggage compensation people. By then, the underwear situation may start to get a bit critical. Despite my resistance to such things, I may need to actually go shopping.

PS: L’shana tova. (Happy new year in the Hebrew calendar, thus begins the year 5770)

Update Monday: Still no suitcase.
Update Tuesday: Still no suitcase.
Update Wednesday: Still no suitcase. BMI instructs me to contact the Luggage loss department. Ugh.
Update Thurdsay: Alas...
Monday, September 14, 2009

Shelob, Aragog, or Charlotte


According to the British Arachnid Society, there are no spiders in the UK that eat people. However, looking at the rather large spider who has taken over my backyard in Oxford, I have my doubts.

You can see her for yourself in the picture. For reference, the garbage can in the background is a full size 40 gallon container (150 liters). The spider is about 2.5 cm from fang to spinnerette –a bit over 5cm long if you include the legs. I’m not positive, but I think she is an Argiope Bruennichi, based on the size and the striped legs, but the body doesn’t look quite like the pictures I find online (Any spider experts out there want to comment on this one?).

I had known about the spiders of unusual size (S.O.U.S.) in this country even before I moved here: I had had a frightening close-encounter with a British SOUS on one of my visits to Oxford before moving here (a story for another day). Admittedly, The British spiders aren’t nearly as nasty as the beasts that live in Australia: for example, the Funnel-Web can deliver enough poison to kill a human within 40 minutes, and can bite through most canvas sneakers. This seems to me to be a good reason to avoid the whole continent.

Despite the favorable comparison to the bigger and badder Aussie variety, the somewhat less deadly British critters still give me the creeps. There is some evidence that being afraid of spiders is learned behavior, and children do not naturally have this fear. Nonetheless, the trope of the deadly spider is certainly a common one: Aragog, Shelob, Charlotte. Ok, maybe Charlotte was not supposed to be so threatening, but E. B. White conveniently left out the part of the story where Charlotte mates and then kills and devours her lover. (She lays eggs, so it probably happened). Probably White was censored by his editors since it is a children’s book and one wouldn’t want them reading about spider-sex.

The lifecycle of most of the large British spiders is such that they are born in the spring, they grow through the summer, and get extremely large in the fall just before they mate, lay eggs, and die. I’m traveling for the next three weeks with only one more two day stop back in Oxford, and I’m hoping that Shelob in the backyard will hurry up and get on with the mating, laying eggs, and with luck she will be stone-cold by the time I get back. As far as encouraging the mating part, I left a disco ball in the window and some incense in the backyard.
Tuesday, September 8, 2009

Condensates - the Borg of Physics

Many phases of matter consist of some highly organized arrangement of constituent particles. In many such cases of interest so-called “condensates” have the property that every particle contributes to the overall collective quantum properties of the whole. Not to make too dorky an analogy for an already geeky subject: you might think of it as the Borg from Star Trek – a communist collective of particles each contributing to an overall unison.

Once you have an organized ground state, it is a natural question to ask what the low energy “defects” of this ground state, (the quasiparticles) look like. Indeed, in most cases, it is these quasiparticles that determine the interesting physical properties of the phase of matter in the first place. All of the particles have fallen into line perfectly making a featureless background, and what you notice most in the experiments are the few regions where something different is going on. A next question to ask is what happens when you have a lot of these defects. Can the defects now start forming their own organized collective – their own Borg?

At the Quantum Hall workshop at NORDITA this month there has been a lot of discussion of what kind of condensates, or new phases of matter, can form from collections of quasiparticles in fractional quantum Hall states. This is an old question that dates back to the very earliest days of quantum Hall effect. As many people reading this might already know, very shortly after the discovery of the nu=1/3 fractional quantum Hall effect, Bob Laughlin gave a beautiful theoretical explanation of how electrons in high magnetic field can condense into a new quantum phase of matter (a Borg of electrons), thus explaining the experiment. However, very soon thereafter, additional quantum Hall effects were discovered (the 2/3 effect, the 2/5 effect, and so on). Laughlin’s theory did not fully explain these. It was Halperin and Haldane who realized that the defects (the quasiparticles) of the nu=1/3 effect can themselves organize, forming further new phases of matter. The resulting picture was a recursive construction of defects condensing then new defects forming within these new condensates.

So why revisit this issue now? Well, the new twist is an entirely new class of more complex and interesting quantum Hall states – the so-called “nonabelian” phases or “nontrivial topological” phases (drawing a distinction that all of the abelian phases are now considered “trivial”). In these cases, the quasiparticles, in addition to carrying charge (and fractional statistics), also carry interesting topological quantum numbers. It is not so obvious how such a thing can form a condensate at all, or whether it would want to do so.

There have been several approaches to addressing this problem. The first set of approaches attempt to condense the nonabelian anyon by forming a topologically trivial combination of quasiparticles and then condensing the combination in the same spirit as the old Halperin-Haldane hierarchy.

(1) An approach by Bonderson and Slingerland combines a pair of quasiparticles on top of each other in a topologically trivial combination then condenses these pairs. A more recent paper by same authors plus Moller and Feiguin shows some nice numerical data showing that these trial states are actually quite competitive for experimental systems – although from the data I saw, it was not completely convincing that there was any regime in which they clearly were better than more conventional trial states. Nonetheless, they seem to be now in the running as something that needs to be seriously considered.

(2) An approach by Levin and Halperin (neither of them happen to be at this conference) is to form a topologically trivial quantum superposition of states before condensing. (Not surprisingly, the resulting states lose all of their topologically interesting properties after the condensation ). There does not appear to be much experimental or numerical evidence of these states being realized, even for model systems.

(3) A third approach by Hermanns is a bit more confusing to describe. At first I thought that it was probably incorrect, but now I think the construction makes a fair amount sense although there are some pieces of the argument that still seem a bit mysterious to me. I’ve agreed to be on Maria Hermanns’ thesis committee, to be her “opponent” in the Swedish system, which I gather means it is my job to find holes in her arguments, so I’ll be studying this a lot more in the next few months.

(4)In the work of Schoutens and Grosberg a condensate naively looks a bit different. In this case, a condensate is made by forming a maximum density droplet of a particular quasiparticle with nontrivial topological quantum number . This case can be analyzed in great detail – determining not only the details of the condensate (which is a known phase) but also the behavior of the edge separating the mother and daughter states. (See below however, the work of (6) seems to be able to phrase this condensation again as a boson condensing).

And there are yet more approaches. In the above approaches, all of the quasiparticles form liquids. There is another possibility which is that all of the quasiparticles form a solid. Solidification would usually be considered uninteresting from a topological perspective, but here since the quasiparticles carry topological quantum numbers something more interesting can happen.

(5) In this picture discussed by Gils, Trebst, and friends Gils, Trebst and Friends, one might have the charge of the quasiparticles pinned in some sort of lattice, but the topological quantum number may still be able to hop around. Although the hopping my be very weak, at very low temperature and long time scale, in principle the topological quantum numbers will settle into a unique “condensed” ground state of their own hopping problem. This is somewhat like electrons forming a Wigner lattice and then looking at the spins on the wigner lattice, which at low temperature, align to form a ferromagnet (or antialign to form an antiferromagnet, which is more typical).
Finally, there is the world of more abstract nonsense:

(6) And a more abstract discussion of condensation was given by Slingerland and Bais. While perhaps a bit daunting at first, this paper is well worth the effort to read. These authors have constructed a generalized paradigm to describe condensation of one topological phase within another topological phase. The general rule is simply that you have to find a particle that is topologically a boson, then you can condense it. Anything that is not “local” with respect to the boson cannot live within the new phase, and you have to identify any two particles that differ from each other by the bosons. (There is a subtlety having to do with particle branching that I will not explain here). Pretty much all of the above cases can be described within this formalism in one way or another. Further, coset TQFTs can be described nicely within this formalism too (which I find very pretty). The down side, as in any abstract nonsense, is the generality is frequently a disadvantage as much as an advantage. Since you can describe pretty much anything, it does not give you hints as to what thing to expect.

At any rate, there are a whole bunch of ways to describe condensation of topological phases within topological phases. Seems like a popular thing to be studying right now. Resistance is futile….
Sunday, September 6, 2009

Jumping out of Airplanes

Eddy Ardonne is an avid skydiver. He is currently an assistant professor at NORDITA in Stockholm where I am visiting this month, and he frequently offers to take people skydiving if they so happen to be interested. Smitha Vishveshwara*, who was once Eddy’s officemate, made a jump a few years back and loved it. My colleague from Ireland, Jiri Vala, was absolutely determined to try jumping this week and encouraged me to go too.

Now, to begin with, I’m a guy who doesn’t even like to drive in a convertible because I don’t like that much wind in my face. Why on earth would I want 120 MPH of wind in my face? I’m also rather afraid of heights (yes, I know, I’ve rock climbed in the past, but I never like being near a cliff unless I’m in my harness and anchored in). But perhaps because I was completely terrified of the idea, I was also curious about it, so I started doing some homework to find out, just how dangerous is it?

Being a statistics geek, the first thing I found was that many of the statistics that you find on the web are totally bogus comparisons.

The best verified figure I could find is that in skydiving there is roughly a 1 in 100,000 chance that you will die on any given jump. It might be a bit lower for certain types of jumps, or certain jumpers, and a bit higher for others. But very roughly, this seems always to be the right number**.

But back to bogus statistics: Here’s a statistic that gets thrown around an awful lot:
“Each year about 30 people die skydiving in the United States, and that's out of over 2 million parachute jumps. Given the odds, you're better off skydiving than let’s say driving a car. Every year, over 40,000 people die in traffic accidents”

Similarly many websites state that
“you are more likely to die driving to the dropzone than during your jump”

I’m calling a loud foul on both of these: The fatality rate for driving a car in the US (and most of the western world) is roughly one fatality per 100 million miles driven. So a single jump has the same fatality rate as driving a car one thousand miles. Spending an hour making a single jump is over 100 times more dangerous than driving a car for the same hour. Perhaps it is surprising (even impressive) that jumping out of airplanes is not more dangerous than this, but still the statements being made on the web are clearly inaccurate. I’m not particularly afraid of driving a car for a thousand miles, so there is not really much good reason to be afraid of making a single jump. However, if you make it a habit of jumping out of airplanes, you have to accept that it can start to become a significant added risk.

While I was searching for more statistics on the matter, I found quite a few interesting things about skydiving injuries. One of the strangest facts is that for solo student jumpers (not jumping in a tandem) apparently women have over twice the fatality probability than men. No one seems to know why this is, but it is an established fact. There are some other interesting statistics regarding how many times a fatality occurs from a real splat (no parachute deployment), versus from other means such as mid air collisions, improper landing with proper chute deployment etc. It turns out that the real splats account for less than 30% of the fatalities.

Another interesting stat (which is harder to pin down from data available) is that non-lifethreatening minor injuries are apparently pretty common - the “injury requiring medical attention” rate is roughly 1 out of 1000 jumps. Most of these are minor sprains, breaks, and so forth. But a few are more serious. If you compare this to say, a few years of participating in any other sport, you would probably have a similar rate of minor injuries. (One should be warned however that certain medical insurers do not cover skydiving injuries whether or not they are minor).

Anyway, Jiri and Eddy did go jumping yesterday and they both came back in one piece. I didn’t go. It really came down to a decision of whether I wanted to spend most of a day preparing for a 60 second drop (which I didn’t’ think I would enjoy all that much anyway). I think the main attraction to the idea was just that I was a bit afraid of it.

Maybe when I’m visiting Stockholm next year I’ll think about it again.

*Congratulations to Smitha on her marriage last month.

**It appears that this number does not include the possibility that the small plane you are in crashes before you jump out of it. It is hard to get numbers on the added risk from plane crashes, but my best estimate is that it is unlikely to more than double the risk.
Saturday, September 5, 2009

Pripps Blå

Perhaps a better name for it should be BLAH.

Pripps Blå is one of the most popular beers (if not the most popular beer) in Sweden. Blå means “blue” and it is pronounced closer to Blow or Blough. On Wikipedia it is explained that Blå is brewed with 51% barley grain, which is the minimal fraction allowed by law if you want to call yourself a beer. (Not sure what the other 49% is – probably some cheaper grain like corn or rice). Despite the jeers of all of the people around me, I actually like the stuff. It reminds me of similarly terrible American beers like Bud Light and Miller Genuine Draft. It tastes roughly like water, and it comes in big aluminum cans.

So here’s the cool thing about Blå. You can get Blå that is 2.2% alcohol (which you could easily drink for breakfast or lunch and not even notice that it was alcoholic) or you can get the 2.8%, or the 3.5% or the 5.2% or the 7.2% (which is pretty strong). And as far as I can tell, they all taste exactly the same. Nice to have options.
Saturday, August 29, 2009

Singing in Swedish

In Swedish, the most common word for “Hello” is “Hej” which is pronounced more or less “Hay”. There is an interesting history to this word posted here about why this greeting was not “the greeting of the masses” until the 1970s. Frequently people repeat it twice: “Hej Hej”. The same website seems to indicate that this implies excitement to see someone (Although the woman at the NORDITA cafeteria seems to use “Hej Hej” for every single customer, and she can’t possibly be excited about every single one).

After a day or two of figuring out that “Hej Hej” is actually a greeting, I started noticing that a lot of people seem to sing it more than say it. Of course not everyone does it the same way, but I’ve heard an awful lot of people who put the second “Hej” almost exactly a major third below the first “Hej”. The Swedish language does have a bit of a sing-song quality to it, but I don’t really detect any other consistent musical intervals in the Language except for when people say hello.

Geek interlude: a major third is a frequency ratio of 5/4=1.25 on a natural scale but is a frequency ratio of the cube root of 2 (1.2599..) on an equally tempered scale.

Speaking of Swedes and music: yes indeed, I have heard a lot of ABBA in Stockholm (Hey, come-on, admit it, you love them too). I was hoping to hear some Ace of Base and the Cardigans too (Yes, they are both Swedish.)
Saturday, August 22, 2009

The International Week of the Gaffnian

Isn’t it great when you manage to get in one room a majority of all the people in the world who are interested in the same esoteric aspect of an already esoteric subfield of theoretical physics?

Keeping in mind that about half of the people who actually care about my particular pet projects within my sub-subfield are actually at NORDITA this week, I took the opportunity to declare last week to be the international week of the Gaffnian, being that most of the speakers at NORDITA were speaking about the Gaffnian in one way or another.

So for the more general physicists in the audience, I’m sure many of you are wondering what on earth a Gaffnian is. The terminology is a mathematical-phonetical-linguistic joke that I managed to get into print. The Gaffnian is a trial quantum Hall wavefunction we introduced in several years ago in this paper (In the paper, the joke is explained… sort of). For the experts it was proposed to describe the nu=2/5 quantum Hall effect, but probably instead describes a nearby critical point. This Gaffnian wavefunction has remained a bit of an enigma. It is nice because it is based on a conformal field theory – but it is not nice because it is based on a nonunitary CFT, which means that it cannot represent a state of matter with a gap (if it is a critical point it makes sense that it has no gap). However, the numerical overlap of this trial wavefunction with other wavefunctions, such as the composite fermion wavefunction, believed to represent the ground state of a gapped state of matter is about 99% even for reasonably large finite sized systems. So apparently the 1% difference between these two wavefunctions makes all the difference in the world to the physics. How this 1% changes the story is not very well understood.

A year or two after we introduced this Gaffnian wavefunction, interest boomed when Bernevig and Haldane pointed out that the Gaffnian is actually just one of the simplest of many possible trial quantum Hall wavefunctions (for general nu=k/r) that can be described as Jack polynomials (these are a family of special functions with lots of nice properties). But after a fair amount of grief it turns out that, except the previously known Read-Rezayi series, all of the Jacks suffer from the same nonunitarity problem that the Gaffnian suffers from – so they probably describe a whole set of quantum Hall critical points. The reason the Gaffnian is so interesting to study is because this is the simplest of the nonunitary Jacks and presumably understanding the physics in that case will tell us a whole lot about the more general cases.

The Gaffnian also has an appealing advantage (not shared by all Jacks) that it is the exact ground state of a particularly simple Hamiltonian. As such, quite a few exact statements about it can be made. This gives one a starting point for analysis that gives a bit of hope that we might actually be able to unravel its mysteries.

Stockholm

When I wake up in the morning in Stockholm, I catch the subway at Thorildsplan, change from the subway to the bus at Odenplan, and then get off the bus at Valhallavägen. I somehow have the feeling I am living in a Marvel Comic. Should I have a constant fear that Ragnarök and Fenris Wolf are just around the corner?

Making the eternal conflict between good and evil all the more cartoonish (or maybe making the eternal conflict between heavy metal and the rest of the world more obvious) it seems that every word in the Swedish language is decorated with an unreasonable number of umläuts.

But Marvel comic jokes (and jokes about characters in Marvel comics) aside, Stockholm is actually a very nice city. Very much as you might expect of a northern european city, Stockholm has its share of canals, bridges, pedestrian areas, open air markets, gardens, castles, museums, cafe's, and tall blonde people. Overall not much to complain about.

The NORDITA center (Nordic Center for Theoretical Physics) moved to Stockholm from Copenhagen where it had been for half a century (This move struck me as a great loss for Copenhagen). Like the KITP and the Aspen Center, the idea of the center was just to have a place where theoretical physicists could come and hang out for extended periods of time and work together. They've done a great job of making it comfortable and pleasant for all of their guests. I've been here for almost a week already and I'm staying three weeks more --- I think this is going to be a very nice stay.
Saturday, August 15, 2009

The Summer of Being Erdős

Paul Erdős (pronounced Air-Dish) was one of the most prolific mathematicians who ever lived – he was also one of the most eccentric. His life has been immortalized in the documentary film “N is a number” and in the bestselling book “The man who only loved numbers.” (which is a very fun read, even if you don’t like Math).

One of the unusual things about Erdős is that he was a vagabond: Except when he was very young, he never actually had a home - he just spent his life hopping from one mathematics conference to the next. And when there was no conference to visit, he would just pop in on one of his many collaborators for several weeks, working on a mathematical paper or two for a while, before moving on to his next visit. All of his possessions fit into one suitcase. When I read about this lifestyle, it certainly seemed a bit crazy.

I wish I could claim to be as prolific and as important as Erdős was. I’m not. But I am starting to share one of his other eccentricities – being a vagabond. And it isn’t nearly as crazy as it sounds. You see, over the course of this summer, I have been hopping from one locale to the next, living out of a suitcase. Between the day the spring semester (Trinity) ended (June 18) and the day the fall semester (Michaelmas) begins (Oct 4), only a mere handful of days will be spent at my “home” in Oxford. The rest of the time I’ve been all over the map: California, Italy, Colorado, Netherlands, Germany, Sweden, Ireland, …. Right now, I am about two-thirds the way through the summer, and I’m still holding up pretty well (an annoying cold and a damaged rib not withstanding). Living out of a suitcase turns out to not be that difficult.

Wherever I go, there is interesting physics to be done, and interesting people to talk to. And in the modern era it is not even that difficult to keep in touch with friends and family wherever I happen to be. I’m not sure I could reduce all my worldly possessions to one suitcase, but it might not be such a bad idea to try

Oh, and for those who want to know, my Erdős number is 3 (via Mike Freedman and Laszlo Lovasz).