Imaginary Potential

I was reading a book called “The Revenge of Anguished English”, and although the content doesn’t live up to the promise suggested by the title, there was a nice physics typo mentioned near the end: “He got his degree in unclear physics”. The question is whether that tiny letter substitution makes that much difference to most people who might be reading a newspaper biography of someone. Are nuclear and unclear synonyms to everyone who doesn’t have a physics degree? I would guess that for all practical purposes they could often be interchanged. I don’t want to be snobbish about it - I’m sure that I wouldn’t blink at an article about”More sculpture” when it was meant to be about “Moore sculpture”. Perhaps nuclear physicists should be upfront about it and just go with it. An “unclear power station” sounds quite aesthetically pleasing, as if it faded into the background on sunny days. And at least G.W. Bush could talk about such an entity without inducing a snigger from every science graduate (and indeed every literate person) in the English-speaking world.

You know, I love my work, but there are days I wish I did physics with cooler demo-potential.

I wasted four hours last night bughunting something weird in my analysis code. It’s silly, so I’ll spare you the details.  I spent four hours watching variable addresses magically and erratically change, then gave up and asked Eric(office next door.)  He walks in, patiently listens, and points out the problem in under a minute.  Thanks, yo.  He was really humble, saying that he didn’t even understand what the code was doing.  All I needed was the perspective of someone who wasn’t on the verge of seething murderous foaming rage.  It never ceases to amaze me how sometimes someone with no experience with the particulars of the problem is the best person to solve it.

During my bughunting, I realized I needed to take a break to avoid taking an axe to my workstation.  To use the time  constructively,  I was (re(re(re)))writing the introductory part my thesis.  This is hard, because I’m supposed to sum up the history of particle physics in two paragraphs to sound like a linear, errorless set of discoveries which culminate in my Ph.D.

I found out that John Dalton got the chemical formula for water wrong: he though it was HO.  Can’t be right all the time, eh?  Here’s a nice historical overview of the development of the periodic table which is helpful if anyone needs to write an intro section.  The best part is it shows you many of the blind alleys that happend along the way.  This is real science.  100 people trying, 100 attempts, and maybe only one is the least wrong.  Dalton also believed that atoms pack like hard spheres, that their size was proportional to their mass, and that gasses were made of individual atoms.  This didn’t mesh with the work of Gay-Lussac and Avogadro, but because the whole atom thing was clearly a good idea, people wanted to believe these things too. “…the full acceptance of the atomic theory and Avogadro’s Law took almost 50 years.”  Life goes on and empiricism plus self consistency is a narrow path.  I wish they could teach science this way.

Open House, Part II

The open house is finally over! Having the newbies here was actually a lot of fun, but a bit exhausting. Towards the end, I think, you straight up run out of things to talk about with them. The week included many free meals and coffees (graduate student staples) and was topped off by a kegger at my place. That’s right, a physicist kegger, and it did not disappoint.

Though, as might be expected, the proportion of men to women was not exactly 1:1, it actually didn’t seem like such an uncool party. Co-blogger Bonna showed up, and, as I remember it, I tried to engage her in a discussion about love, then spilled white wine all over her. 

And then…the cops showed up! They had received “numerous complaints” about the noise! No greater compliment might be heaped upon a physicist party! The po-po and I had a very cordial exchange, where they basically made me close all my windows. Then, seeing the glass bottles on the sidewalk that the recycling truck had failed to pick up that morning, the following exchange went down

Cop: You’d better pick all these bottles up too. People come out drunk from parties, take glass bottles and will smash them against windshields.

Me (a little tipsy, and genuinely puzzled): But you don’t understand, we have a bunch of physicists in there. 

Needless to say, I cleaned up the bottles. 

Cheers to Julia for pointing this paper out to me: Planetary-Scale Views on Instant-Messenger Network,  Its nothing exotic, but what a data set:  They had access to the compete MS IM dataset, modulo individual identifiers.  They think they got half of all the conversations during the study.  30 billion conversations, 240 million distinct users, unless you assume a significant number of multiple accounts and robots, which I don’t think was addressed.

They get lots of broken power laws (yawn), and estimate the average degree of separation is 6.6, (double yawn), or that people in the 20s-30s are over represented with respect to the world population (ZZzzz…).    There is cool stuff though, like inter-gender conversations last longer on average than single-gender, and there’s some weird off diagonal nodes on reported age correlations or participants. There’s a cool map of users per capita of the world, and you see a significant asymmetry in the US, with more users per capita in the western half as in the east, with about the same density as in Australia.  This is clear anticorrelation with population density, but it looks cool.  People in Arabic nations seem to have significantly long conversations on IM, why this is is not immediately obvious to me.

There’s some weird extremities of the dataset: The tail of the AddBuddy events distribution shows that some people actually have 600 contacts (the maximum) on IM.  Wild.  This smells like robots to me.

Awesome. I love it when people do good old-fashioned straight-up QCD Pheno. RHIC sees tons of cool effects where the theory just can’t cut the muster, so I get really excited when someone hits QCD head-on, instead of doing something easier, or unfalsifiable.

So I just read this paper this morning, which basically extends DGLAP parton showering to include iteractions with Quark Gluon Plasma. This is pretty cool, as that it seems to qualitatively reproduce some of R_AA supressions. Sad thing is they neglect the reaction of the medium, so I doubt this will describe the mach cone, which is one of my favorite things out of RHIC. Can’t have it all, I guess.

In case you’re wondering, RHIC is a versatile collider on Long Island, which collides combinations of protons, deuterons, copper ions, and gold ions. The goal is to study lots of processes, but most significantly to create really hot, dense conditions where we may be able to observe a phase transition in QCD to something called the quark-gluon plasma. Maybe we already have seen it, but the theory is wicked hard, and no one is certain whether there’s really a phase transition or not. Whatever they are making, the “medium” is hot, dense, and is pretty much in thermal equilibrium as its expanding. They also know that it smears hadronic information, but electromagnetic stuff passes through unscattered. The hadronic smearing I’m talking about seen in the R_AA plots, which are ratios of stuff from gold-gold and proton-proton collisions. The basic idea is, there’s a hard scatter in pp or AuAu which are essentially the same, the energy has to pass through the medium in AuAu, and the distributions are really different. You can read more here from the STAR collaboration. The mach cone thing I mentioned is a hunch that people are seeing something analogous to a sonic boom as partons traverse the medium. This is fantastic, because if you can measure a mach cone, you can measure a speed of “sound.” If you can find a place where the speed of “sound” suddenly changes, thats pretty good evidence for a phase transition, which is the name of the game. Heres some slides of a talk I saw at DIS last year. Its a good introduction and overview to RHIC.

For those of you interested in pattern classification, machine learning, etc, there’s a really nice package called TMVA, which contains a ton of multivariate techniques which are fairly easy to integrate into High Energy Analyses, as they are a ROOT extension. Even if you don’t do HEP, they’re nice because all the methods have comparable inputs, so you can test tons of different ones without a big development hit. I’ve only futzed with the Multi-Layer Perception package, but that was pretty quick and painless to implement. A buddy of mine at H1 used it for electron tagging, and tested like seven different methods before settling on a Boosted Decision Tree. I mention this now, because Anselm Vossen just released a couple of lecture notes (I think they’re from the CERN Computing School) on the principles of some of the implemented techniques specifically Support Vector Machines and one which has a nice discussion of data preprocessing for MVA. If your shopping for selection criteria, check em out.

That reminds me, a reader “A. Game Coder” commented before that they’d like to see more posts on computing in Physics. While I’m thinking about it, check out the slides from the CERN summer school in 2006 and 2005. Lots of fun stuff like genetic algortihms and management of large data sets.

In the last few days, there’s been a few interesting surprises in Astrobiology/Astrophysics:

Cassini has confirmed that the surface of Titan is shifting fast, and in a really weird way, which could indicate that the whole surface is floating on top of liquid, ie an ocean. This is a big if, but Titan has always been a favourite speculation for extraterrestrial life anyways, since it’s surface has lots of water ice and simple organics like methane and ethane. It also has surface lakes of methane, which could support life. But if you live in a methane lake, its living, but can you really call it a life? This was all postulated before from satellite data, but since the atmosphere is so thick, so they made these passes a big part of the Cassini mission. Cassini will make its closest pass on Titan on March 25.

Meanwhile, Hubble confirms methane on the atmosphere of an exoplanet, which is getting sexed up by the media as potential extraterrestrial life. The Interviewee for New Scientist stressed that this planet is too close to its sun for what we would call life, but its interesting from the standpoint of planetary models. This planet has way more methane than we would expect from something of its size, indicating that we don’t really understand planetary formation so well.

Lastly, yesterday the SWIFT observatory detected the brightest recorded Gamma Ray Burst ever, with an afterglow in the visual spectrum bright enough to be seen with the naked eye. What’s really cool is that it had a red shift of 0.94, which makes it the most distant object ever observable with human vision alone. The new record is now 7.5 billion light years away, and the previous winner was 2.9 million. They also state it was the most luminous object ever recorded by humans, being “2.5 million times more luminous than the most luminous supernova ever recorded.” It also has the most superlatives attributed to it, like, ever.

…were written by Bonna, in her post earlier today. I actually teared up while reading the post about how life happens in grad school. I seem to be doing that a lot lately; I’ve become overly sentimental in my (early!) middle age. Sometimes commercials with cute puppies and babies can get me farklempt. 

 The truth is that Bonna is absolutely right, grad school can be a pretty miserable place (I am in no way mad at you for saying this). You can lay awake in bed, unable to sleep, anxious, wondering if this was really the right decision. You can think about your high school and college friends, who have jobs that seem pleasant enough, that make good money, and leave them with the free time to enjoy it. You can wonder and doubt whether or not that the world of books and papers that contain breathtaking physical ideas and mathematical beauty can really hold a candle to the world of a social life and deep interpersonal connection. And by “you can,” I mean, “I have,” and at length. 

And the truth is, like Bonna, I had no idea that it would be like this at the end of college. Grad school just seemed like a natural extension; I loved and was good at taking physics classes in college, why shouldn’t I continue that? I would even get paid for it! But life kicks in after college in a way that I find difficult to explain (but is probably appreciated by everyone in their mid 20’s and beyond). 

 Chatting with Bonna today, I wondered if, I could meet younger Dave, I would tell him to go to graduate school or not. I told her that I would probably tell him not to. Then I went back to the library and read some incredibly beautiful stuff (see post below) and remembered why I was here, why I loved physics so much, and how, silly as it sounds, my life would be somehow less rich if my brain had never touched such wonderful ideas. So I guess what I would tell younger Dave (YD) depends very much on which day you catch me on (and how research is going at that particular point). 

 The debate I was having with Bonna, and others, about this, is whether or not one should tell open house students “the whole truth,” about grad school, and I think the answer is no. These kids, like YD,  are full of optimism and confidence that physics is what they want to do (”What else would they do?” they think). One shouldn’t (and one couldn’t) dissuade them from going to graduate school in general. When, as a prospective, I heard that “graduate school is a love-hate relationship,” the full implications of that could never be conveyed to me. In fact, that sounded like a more-than-fun concept. Once the students here, I feel like our aim is to convince them that MIT is a pretty damned great place to spend your graduate years, if you’re intent on spending years in graduate school. And that’s a sentiment that I believe 100%, without reservation (though I guess the weather could be nicer). 

Anyway, I’ll blog more about my experiences with the open house once it’s over. The final event is the kegger at my apartment tomorrow night! (And who was just saying life had to be different after college?) 

The supersymmetry club is hitting Seiberg Duality this week! In preparation, I’ve been rereading the very good Argyres notes (here linked is strictly the ‘96 Weyl spinor version; If you want the Majorana version, I might ask you, why do you like unhappiness and pain, sir (or madam)?), and also the book by Terning (which I find less helpful on first reading, but very beautiful once I sort of know the stuff already).

 I also tonight started reading these notes by Strassler, which (though I’ve only read the first fifteen pages or so) are freakin’ incredible!  Why did nobody tell me these notes were so good?! (Answer: Tom and Qudsia have been telling me to read these notes for weeks now). For those who mournfully don’t know about the beauty of Seiberg Duality, there will surely be an explanatory post to follow. I seem to use lots of parentheses in my posts….