I've been at a workshop on theoretical aspects of cosmology for the last two weeks. It's called the PITP and is extremely interesting! It's held every year at the Institute for Advanced Study, which is an independent research institute close to Princeton in New Jersey.
In our information packet, there was a page-long warning about Lyme disease, which can be caught from ticks in the wilds of the campus. Deadly invisible animals everywhere - soon I'll get homesick! On the first day, everyone kept close to the path just in case they were attacked by giant marauding arachnids.
About 24 hours after we arrived a shuttle was arranged to drive us to the nearest supermarket - only 20km away! Princeton is anything but a bustling metropolis, if you get my drift. Entering 'shoprite' or something I had to negotiate 20 or so shelves stuffed with cookies, followed by an aisle of cakes in plastic containers covered in heaps of icing, followed by yet more cookies! After traipsing all over the store collecting non-poison, I staggered back onto the shuttle carrying 6 bright yellow bags of groceries. Hopefully enough to feed me for seven days!
During the check-in process, we were given a box of afternoon tea refreshments, the centrepiece of which was a rather exciting looking sandwich. If you will permit a short excursion into the fascinating area of US farm subsidies; a push for healthier milk led to the popularisation of skim milk products. So far so good. But the diary industry was left with an excess of cream. There is really nothing sensible to do with cream except to eat it. So the diary lobby (yes! It exists!) has pushed for wider consumption/subsidisation of cheese and butter. Which kinda defeats the purpose of skim milk in the first place.
This sad fact impinged upon my life thusly - the upper part of the sandwich bread was encrusted with a delectable layer of melted cheese. Don't get me wrong, I actually rather like cheese, but have been rather allergic to milk products for the last two years or so. The sandwich upper was lain aside. Beneath two slices of the rather less appetising orange american cheese shone sunnily forth. They too were consigned to the purgatory of the adjacent fold of grease proof paper. I was suspicious that the sandwich may be built upon a foundation of milky creamy stuff, but it passed the sniff test. I proceeded with abandon. It was scrumptious. Perhaps a little too scrumptious. Forensic analysis of the crumbs revealed, to my utter horror, that the bottom of the sandwich too had a stealth encrustation of baked cheese.
Having not eaten this much of the forbidden fruit in many months, I was now curious (like the scientist I am) to see what would happen. I am pleased to report that a repeat of the precipitous weight loss that marked the last half of 2009 did not repeat itself. However the usual milder response of fatigue and irresistible drowsiness while seated has recurred. Sitting in 5 hours of lectures a day in front of the creme de la creme of theoretical physics was daunting enough. Spending most of that time in bizarre, cheese-filled dreams, was slightly embarrassing. Fortunately at this sort of event jet-lag and workaholism is not so uncommon that sleeping all day is particularly out of the ordinary. Still, when I'm able to control my diet better I will have to return to the webcasts (as yet only fabled) and see what I missed out on. Moving to the back of the theatre and less comfortable seats helped to an extent!
For the record, all the speakers here are highly regarded researchers in their fields, including Susskind, one of the inventors of string theory. Ed Witten (the only physicist to ever win a Fields Medal) is not officially part of the program, but has joined many of the sessions. It is slightly intimidating to be amongst people who would eat my hardest research problem for breakfast. So I have to keep it a secret! As my research is tangential, I do not know most of their work except by reputation, which is also slightly awkward. E.g. "Hi, I'm Casey. I hear you do good work, but I have no idea what it is..."
On Thursday afternoon I walked through the town, visiting the record store, a small park with a list of regulations and rules about 8 feet high, and saw many of the famous buildings in Princeton, including the stairs that Russell Crowe dropped books down in the movie 'A Beautiful Mind', about the economist and Nobel Prize winner John Nash. The next day at lunch the REAL John Nash was sitting at the next table! With a few Nobel Laureates at the cafeteria I could almost be back home at Caltech!
Also worth mentioning is the exterior shots of the "Princeton-Plainsboro Teaching Hospital" in the television series "House" is actually the Frist Student Center on the Princeton Campus. Like everything else, however, it's actually filmed and produced in LA.
On Friday afternoon we were finally released from the rather strict schedule we had been following (wearing a name tag at all times is compulsory!) and, throwing a spare shirt or two into my capacious laptop bag, I sprinted for the train. Except that the ambient temperature was about 40C, so my sprint was more of a purposeful melt. If it had been much hotter, I could have exploited the Ladenfrost effect and scooted there on a frictionless layer of steam. Would have simplified the calculations too!
To the train! Before long I was once more in New York's Penn Station, which have all the charm of a subterranean Burger King drive-thru, but a worse smell. In particular, access to the platform from the concourse is via a stairway too narrow for two (normal sized) people to pass, and platform numbers are not announced until 10 minutes before departure. In contrast, for instance, every railway station I visited in Russia was designed and built exquisitely to corral large volumes of human and freight traffic in all weathers and temperatures with maximum efficiency. I am aware that Penn Station was originally a full scale replica of the Baths of Caracalla, with rolling stock instead of a hypocaust, but its loss is an indelible stain on the architectural legacy of the entire United States.
I had received word (via the customary homing pigeon) that my CS host for this weekend K was running late, so rather than brave the metro tunnels I emerged in the sunlight. Elementary arithmetic soon had me zigzagging south east towards my destination. I arrived in time to buy some cool drinks and hang my new hammock (ordered and delivered to Princeton by Amazon Prime!) on the roof before I was joined by K and another CSer, H! Sadly most of the view is blocked by the rampart when sitting in the hammock, but the sunset and sky was, if anything, in bolder relief.
Returning to the blessed cool of air conditioned comfort below we ransacked the fridge and produced a very passable pasta sauce. There is nothing quite like a variation on a theme!
Over the next few days H and I saw Captain America (from the front row) which very, very nearly exceeded my extremely low expectations, but was otherwise fun. We purchased some cupcakes from Sugar Sweet Sunshine only to be served by someone from Sydney! Graduated from Strathfield in 2005, the same year I did! I sometimes try and imagine the tangle of lines embedded in 3+1 spacetime by the movement of people from place to place, and how they diverge and clash again. It was still extremely hot, even with the AC on, except about below the knees. On Saturday evening we held a party on the roof, to which about a dozen brave souls turned up. The weather held, the hammock bindings held, the alcohol supply held. Even K only triggered the emergency alarm once!
Outside the cinema H and I had been bailed up by a journalist who wanted to ask us our opinion of the recently reported death of Amy Winehouse. Aside from the usual questions, one in particular stuck in my mind. "Do you know anyone with whom you would want to intercede?" At the time I answered that I thought doing so would probably only heighten a feeling of condemnation and isolation, as it apparently had with Amy. I'm still inclined to think that to assume I (or anyone) could 'save' someone from themselves is at best naive and at worst condescending. In my opinion the gifts and privileges I've received, through no fault of my own, are much too valuable to risk on what I see as rather juvenile chemical attempts at escapism. That, and I prefer my experiences undercooked. I've travelled far and wide, however, and I'm aware that my feelings and rather hard line in this matter are certainly a minority, and possibly unique. It's not that I'm overly cautious or averse to danger. Just stupid, pointless danger!
Later on Sunday I met K one last time at Bryant park and we had Thai noodles for dinner at a nice place near 36th and 8th (I think??). After exchanging the requisite keys I bolted for the station, and once again immersed myself in the company of peculiar people. Nearly everyone had an iPhone, including me. Though mine is increasingly unusable due to a large crack in the LCD and fluid leakage. The exterior of the phone remains pristine after nearly 2 years of ownership, so I'm a bit cheesed off about the whole thing. Planning an upgrade to probably a Samsung+Android combo in October so I can run some UNIX shell and ssh directly into the machines I use at work. Then I can make Linux move files with a frustrating keyboard and terrible user interface from the comfort of some lecture theatre I would otherwise be sleeping in!
Back at the IAS, the weather had turned. On Monday it rained heavily for most of the afternoon. A few of the nuttier theorists from Stanford expressed a desire to play soccer that evening regardless, however at 7:30 it was only D and I on the pitch, so we threw a Frisbee at each other for a while. In a cooperative sense. After that I was still a bit bouncy, so sandals in hand I took off down Einstein drive towards Bloomberg hall. Through the pouring rain, I splashed in cool puddles down to warm tarmac, pattered over the slick-looking slate, and flew down towards the pond. I paused for a second to catch my breath, and on an impulse pulled my damp teeshirt over my head, rolled it up, and stuffed it down the back of my pants. With a single look over my shoulder to check for oncoming traffic I flickered off on presto footsteps down a path I'd discovered the previous week. A rough dirt trail, it wound between the (rather undergrown) trees of the Princeton forest towards the (little) canal. In the evening's fading light and steady rain I could see moss, grass, dirt, stones, and muddy rivulets, slick underfoot. With short footsteps an unexpected stone is a minor inconvenience, and before long I had reached the water, spanned by a precarious looking wire and wood suspension bridge. I stood in the middle, sandals in hand, watching the rain smash down into the water where I had seen a crane the previous week. Then, lest the setting sun catch me out, I turned for home and zoomed back up the trail. Before long I was back at the pond, and stopped at the ice warning sign. In front of me was the main hall of the IAS. To the right, half a dozen deer looked up, surprised to see me. To the left was the pond, the surface mostly rough and choppy from the rain. Beyond, the sun shone up from the horizon beyond the clouds, casting the underside in that rare yellow glow you see combined with a rainbow about twice a year if you're lucky. I lapped the pond once and ran back via the soccer pitch under scattered yellow light and falling raindrops. Back home, I waited for my hair to dry and tried not to forget. I ran about 2.2 miles (3.6km), which is nearly twice as far as I've run since maybe 2003, and easily the furthest I've ever run without any shoes. It's easy to forget the texture of the ground and what it tells you about where you're going!
I made Pad Thai for dinner, and followed it up on Tuesday with a Moroccan chicken and vegetable stew, which was well received by my housemates, despite a few technical errors in the execution. Next day I experienced sleep paralysis during a lecture, which was slightly disconcerting! Later at lunch I joined an audience of awed grad students and post-docs watching an exchange between Witten and Arkani-Hamed concerning, inter alia, the possibility of the LHC discovering two Higgs bosons before next summer, thus simultaneously disproving both natural and fine-tuned models. For physicists, this is about as good as witty repartee and edgy humour gets. Arkani-Hamed, who is also faculty at the IAS, was doing most of the talking. Clearly, he was nearly as awed as the rest of us! My efforts through the last week to think of something sufficiently intelligent to say to Witten finally paid off! I asked if he'd care to take a side on the toroidal event horizon existence problem currently being bandied about by the grads back at TAPIR.
INTENSE NERDINESS (muggles may wish to skip to the end): This is the problem. A black hole is a lump of matter dense enough to trap light. This is a thing called 'escape velocity', which, like most physics things, means exactly what it says. Nothing can go faster than light (which is why we will eventually use nothing to power space ships <--- physics joke), so if light can't escape, nothing can. The stationary, uncharged, non-rotating black hole was the first solution to the Einstein Field equations. Sadly, that won't earn you a PhD anymore. Rotating black holes are similar, but a bit oblate. They too are stable with respect to time, so determining where the 'event horizon', or the surface beyond which light cannot escape, is relatively straight forward.
At Caltech, we're solving (inter alia) the problem of a general black hole binary inspiral, merger, and ringdown. Here's an oldish video of two non-rotating black holes merging: http://www.youtube.com/watch?v=R9HTdpQMAjY. If the black holes are spinning, then the merger process involves an 'elephant trunk' of event horizon emerging from each black hole across space and eventually connecting to its opposite number. Note that at all times the event horizons of the holes are topologically equivalent (continuously deformable) to a sphere. However, it has been an open question for nearly 20 years whether this process can lead to slightly more exotic topologies. In particular, it is theoretically possible that each elephant trunk could connect somewhere half way up rather than at the ends, leading to the (momentary) creation of a torus, or doughnut topology. Topology just means 'shape'. Note that a typical coffee mug is also topologically equivalent to a doughnut. The discovery of toroidal event horizons would thus complete the holy physics trinity of coffee, donuts, and intense nerdiness.
Technical problems include solving the problem with adequate resolution (on top of which we're just getting). Additionally, finding the event horizon requires an evolution backwards in time from the final, time-stable state to discover which light rays only just escaped to infinity. Infinity is where escaped light rays go. Lastly, not all observers would see the same thing. The event horizon is a 2D surface in 3D space, so in 4D spacetime, the event horizon is actually a 3D manifold that separates two regions of space (an inside and an outside). Then what an observer sees is actually the surface of their past light-cone. Even if a whole bunch of observers get together and agree on a global time (like we do on the surface of the earth), this is non-unique. It's called a foliation, or slicing of space time into space-like surfaces separated by small, perpendicular time intervals. In particular, travelling at different speeds leads to different natural foliations. In order to infer the existence of a toroidal event horizon, the network of observers would all have to be travelling at some particular velocity. Noone is quite sure what this velocity might be. There is a good chance we'll have a relatively good answer by 2015, marking the 100th anniversary of the publication of General Relativity by Einstein in it's final, correct (so far as we can tell) form.
END INTENSE NERDINESS: So, an interesting problem. Naturally, Witten stated that it was not his area of expertise and declined to offer an opinion. My feeling is that toroidal event horizons almost certainly do not exist in nature, though I think they are theoretically possible and could be simulated on a computer. There's a diagram in the album somewhere.
That afternoon I attempted to prove the Jacobi identity for spin-0 4 particle interactions using spinor-helicity formalism (with limited success), then walked to the IAS director's house for pizza and pool party. Although no-one remembered that me and another guy were lactose unfriendly, someone else who didn't turn up was, so all was not lost. I hadn't had a swim in a pool since last August (nearly a year ago), and that was just a small pool in a banya in Magadan. Mostly guys, so there was a lot of water-frisbee-polo, splashing, a relay race, swimming under water, and I did a few flips into the pool to assess how much parkour in Orlando had rubbed off on me. Conclusion - don't try a forward somersault on concrete yet. The water was warm and it was a rather lovely evening. Plenty of fun was had by all! Worth mentioning is that the pool was installed by the former director Oppenheimer (probably not personally), who was one of the driving forces behind the Manhattan project, which led to the creation of the atomic bomb. I suppose he needed somewhere to keep his souveniers!
Around sunset I leapt out of the pool like a whale on speed and, scooping up my stuff, ran past a few slightly confused fellow attendees right back down the road to the house. Putting on my shoes would have slowed me down too much! Back at the diggings I listened to "The Book of Mormon" (the broadway show, not the book), prodded couchsurfing for a place to stay on Saturday (success at last!) and got ready for bed.
The rest of the program rushed to a conclusion. On Friday during lunch, Ed Witten was once again called upon for his expert opinion, this time on the 'tau-pi' religious divide. In recent years there has been a push from certain obscure corners of the academic community to use an alternate notation for units of angle in radians, tau. Numerically, tau = 2*pi, where pi = 3.14159... The reasoning for this is best told here: http://tauday.com/. Ed said something along the lines of "it's a bit late now", which I think applies pretty well for people who make a living out of mathematics - they battled past their confusion long ago!
At length I packed my bag, returned my key, posted my leftovers to K and A in NY, walked into town, bought some merchandise, and swung past the exterior set of the Princeton-Plainsboro teaching hospital (from the TV show "House") for good measure (The Frist Campus Center) on my way to the Princeton train station. Before long the density of nerds had dropped to its stable background level, and the wonders of Jersey Transit sped me away, back to real life.
Photos from the trip can be found here: https://picasaweb.google.com/105494084231616659850/NewYorkAndPrinceton