Wednesday, August 26, 2009


So I bought this monitor at campus surplus. When I bought it I hooked it up to a borrowed laptop and made sure that the screen was ok. Immediately after I bought it I hooked it up and it had three little dead patches. Actually they weren't entirely dead just the blue and green pixels were but the red ones for some reason were fine. It has been somewhere along the lines of 5 or 6 months since i bought the monitor and over the course of this time the dead patches have progressed to the point where they are now completely dead except for a very scarce smattering of heroic red pixels. I had thought that the blotches may have been there when I first saw the monitor in the campus surplus but that I just didn't see them (even though they are fairly obvious). I reasoned that surely the monitor couldn't have deteriorated so rapidly as to form these dead spots just from the walk back to my apartment! But the rapidity with which the splotches further decayed into completely dead patches makes me think that perhaps this monitor is older lcd technology than I am giving it credit for and the walk out in the hot sun was indeed a little too much excitement for its diodes.

Because I blame myself for these splotches (either I made them myself by carrying it home in the sun over 12 blocks or by failing to notice them at the store) so I will live with them until such time as either the monitor becomes unusable or I have something called "discretionary income" which is a theoretical object whose existence is inferred by from observing it in other peoples budgets. I mean actual discretionary income not the kind that comes with credit card debt.

However this newest malfunction of my monitor I feel in no way responsible for. I have kept my monitor inside and out of the sun. Of course I have no air conditioning so I have also kept it warm and cozy 80-90 degrees during the day and a nice "cool enough to sleep in" 60-85 during the night. Since I do not have a great deal of money to spend on rent (the thing that inspired me to get my monitor at campus surplus in the first place) I do not consider this lack of cooling to be my fault.
So of course I was aghast when I am browsing one day (ok fine playing games on facebook) and there appears a solid vertical yellow line from hell. For some reason all the pixels about 4 inches from the left of my screen got together and decided they wanted to be yellow... permanently.

I suppose I can understand their distress, I mean after all I wouldn't find turning on and off all day a particularly riveting job but I somehow think it is more interesting than just deciding to get locked to some bloody color of yellow that probably isn't even legal outside of the 70's. The worst thing about this is that because I see yellow it is not just a single line of pixels doing their thing. Oh no, it takes multiple pixels to make any color but red green and blue so the pixels along this line actually have to be working together against me and just to make it clear that they are in fact a unified and organized resistance waging war against my evil screen tyranny. Well this isn't a democracy and if the pixels are reading this I just want them to know, I'm watching you!

Of course there is always the off chance that this isn't actually a rebellion but an attempt at self order against the chaos of reality. A beacon of reason and culture amidst a world that cannot be understood by my pixels 2 dimensional minds and senses. Perhaps my habit of never turning off my monitor has allowed the pixels inside time to evolve and become more than their makers had intended. Then again probably not.

further common exam details

Now that I have had time to talk with my advisor I have a few more details. As it happens 50% and up was a pass and 33% and up was a conditional pass. Also the number of students receiving a pass was about the same as the number of students who received a conditional. I overheard the chair of the common exam committee and another professor talking about the common exam in German. Now I don't speak German so I don't know exactly what they were saying but it involved something about the 90th percentile and conditional pass. When I talked to my advisor he said there were a "few" who did not pass. Also there were a number of faculty who were unhappy with how the lines for pass and conditional pass were placed. I take all this to mean that all but about 10% of the students taking it passed (conditionally or not) and that would mean only 2 or 3 people got just a plain fail. I'm sure the scores were basically clustered around 35-37% and they just had to put a fail line somewhere it would still do something and so they put it at 33%. I bet the people who failed got like 29% or even 30% when just grubbing for a few extra points would have gotten them a conditional. Or maybe it would have just made a whole buch more people fail because now there would be no tail to the distribution.

Also as a correction to what I said before it turns out that in general you will be required to take both 5010 and 5020 in order to pass the common exam if you got a conditional pass. But my quantum mechanics and my classical mechanics problems on the common exam were my strongest problems. Whereas my statistical physics and my electrodynamics problems were a little lacking. As it happens 5010 is about mechanics both quantum and classical and 5020 is about statistical physics and electrodynamics. So because I got strong scores on the problems with topics from the first class I can skip to the spring semester part of the class.

I Passed The Common Exam... Sort Of...

The common exam is the phd physics program entrance exam. You have to pass it in order to be formally admitted to the program. The common exam was what you might call a rather tough test. If you don't pass the test the first time no sweat you can take it again next year, but if you fail it a second time you will not be admitted to the program and therefore cannot receive your PHD, game over. Because the test is so hard and because of the harsh penalty for failing twice if you don't quite pass you may get what is called a "conditional pass" which means that the department will pretend you passed just so long as you get an A- or better in some particular class. Usually that means physics 5010 (a night class taught by one of the most mad scientist like looking professors I know) in my case it means I have to get an A- or better in 5020.

I'm not really sure how I feel about having conditionally passed a test. I won't actually know if I passed or failed the test I took this past Saturday until 9 months from now even though the test got graded 2 days after the test. But one thing is for sure I have never been so happy to get 40% on a test.

Monday, August 24, 2009

First Day of Classes

So the common exam went pretty badly, I don't think I was alone in doing rather abysmally badly so perhaps I will get lucky and the pass percentage will get placed somewhere around 40% Of course I am not really sure I even got that high, it is perfectly possible that I got somewhere around 30%. Its funny but apparently my strong point in physics is quantum mechanics. The only problems that I can consistently do are quantum mechanics problems. I suppose it is because it is all about function spaces and transforms and I have been doing rather a lot of that sort of stuff lately. I spent all day Sunday just lazing about and now today is the first day of classes.

Usually I find the first day of classes exciting and even a little relaxing because I know there isn't anything that needs to be done for the first day. I am not going to go into the class and find out that I forgot about a homework. But now that I am teaching a discussion section of physics 2210 everything is different. The teacher won't even be able to cover a full 50 minutes of material because he has to deal with the syllabus and introduce the T.A.s and the S.I. instructor and of course pontificate a bit about how wonderful and important physics is. I on the other hand have a full 50 minutes all to myself with no syllabus or introductions to fill it up. Worst of all there won't be any homework assigned that early in the class so that means I can't even fall back on that. Right now the plan is to just talk about what vectors are and give a bit of a review for the math.

I guess at the root of my anxiety is that failure as a teacher is fundamentally different than failure as a student. If I fail as a teacher I have harmed me and my students but if I fail as a student my failure harms me only.

Thursday, August 20, 2009

I am a P.H.D student!!!! and I have a box!!!

Like so many wonderful things that have happened to me in my life this happened at the absolutely last possible moment. A couple of weeks ago when I applied to graduate with my undergraduate degree the undergraduate advisor told me that I had a strong application to the graduate physics program. I had been planning on applying to the physics program as well as the math program at the U but according to the application requirements of the physics prorgram they need a physics subject GRE before they will review the application. Apparently this is not actually the case, I finished up my application that I had been intending to put in and a little over 2 weeks later I found out I was accepted. Today I read this letter and went through all the necessary paperwork to become a real grad student.

August 18, 2009

Timothy Anderton
1031 E. 200 S.
Salt Lake City, UT 84102
Dear Timothy Anderton,

We are pleased to inform you that the Admissions Committee of the Physics Department has /recommended/ to the Graduate Admissions Office of the University of Utah that you be admitted to our graduate school. The Graduate Admissions Office/Student Admissions should soon formally notify you of your admission to the University of Utah.
We are also pleased to inform you that we have recommended that you be awarded a teaching assistantship for the 2009-10 academic year. The stipend for the 2008-09 academic year was $12,107 for a Level I position and $14,131 for a Level II position for a nine-month period. You will also receive tuition benefits to cover the cost of tuition. The tuition rate for an in-state graduate student is approximately $4,600 per year. Therefore, this offer is worth approximately $19,000 per year. In addition to these nine month stipends, there are a few additional summer stipends available and you will be able to apply for one of these; they run at ~ $2,000 each. We have also contracted through the Graduate school for a subsidized graduate student insurance program that you will have the option of purchasing (the Graduate School pays 80%). We have recommended you for a Level II position based on your previous experience.

We would like to point out that new graduate students in the Physics Department need to pass a general, comprehensive Physics Common Examination within their first or second year of graduate study before they are formally admitted into the Ph.D. program. The Common Exam will be on Saturday, August 22, 2009 and all incoming students must take it at that time. Those passing the exam are automatically classified as Ph.D. candidates. Those not passing have the option to take the exam the following year. Copies of previous years' exams are available on our website at
Please let us know by */as soon as possible /*whether or not you accept this offer*. *Please send notification of your decision to Jackie Hadley by regular mail at the address listed below, by e-mail at or by fax (801) 581-4801. If you have any questions or concerns, please feel free to contact Jackie Hadley at any time.

We sincerely hope you will accept our offer, and we are looking forward to having you join our graduate program.

Wayne Springer
Associate Professor
Chair, Admissions Committee

What they don't tell you on the letter is that I get a box in the department that people can slip stuff into and I can take stuff out of. I know this doesn't seem like that big of a deal but it is a tremendously big deal to me. I HAVE A BOX!!! it has my name on it and it sits near the front office of the physics department. I will also be getting an office somewhere (which I bet I will have to share with someone) somehow even though this is even more amazing it doesn't seem to have the same resonance that having a box does. An office is just somewhere to sit, the box represents to me that I am somehow open for business academically. Leave your homework here and I will get to it.

The T.A. is:

P.S. The common exam is scaring the crap out of me, I have only been studying for it since Wednesday and I go into the exam with nothing but a couple of pens. In the past couple of days and in the next few days I need to relearn about 30 credit hours worth of stuff... If I weren't so extraordinarily giddy about being admitted and getting paid to be a grad student I would still be studying instead of writing this post. Speaking of which I only have 40 hours 9 minutes and 10 seconds left to study!!! g2g

Saturday, August 8, 2009

Wavelet Transforms and Neural Networks

A single level complete forward neural network with m input nodes and n output nodes can express any linear transformation with an m by n matrix representation. Clearly if the activation function of the neurons is linear on the inputs then no matter how many layers of a feed forward network we had the result would always simply be a linear transformation of the inputs. With a non linear activation function though we can get any function of the inputs at all not just linear transformations. The most common activation functions are the hard threshold function which is 0 below some threshold and 1 above it and the logistic function which is close to 0 for low values and close to 1 for higher values and quickly rises from one to the other in the region of some threshold value.

Now consider for a moment that the wavelet transform is a linear transform and so can be represented as a neural network. Also remember that performing hard or soft thresholding on the output coefficients is simultaneously a means of compression and noise reduction. In fact I believe there is some evidence to believe that stuff very much like this is actually what happens during our brains processing of visual data.

The question I want to ask is does it make sense to think about multi layer neural networks in terms of a redundant dictionary of functions and can we use that to design network update methods. Or does the reverse hold true and could we use neural network update techniques to tell us something about the best m-term approximation in redundant dictionaries problem in wavelets.

Wednesday, August 5, 2009

Brainwave Music

I have been thinking it would be a lot of fun to make something that works like the theremin except instead of using your hands to control it you could use say your heartbeat to control volume and brainwaves to control pitch. I doubt you could really get very good music out of it. Rather like the above experiment but I would certainly love to try.

Tetris and AI

I have been something of an avid tetris fan ever since I bought an old nes cartridge of tetris at some point during junior high. I have spent whole days doing nothing but playing the classic nes version. A couple years ago I bought a ps2 version of tetris (tetris worlds) and it has quite a number of different modes of play but still doesn't hold a candle to the nes version due to certain horrible choices on the part of the game designers.

At any rate the pacman competition has given me a certain amount of perspective on how hard game playing can be as a computational problem.

At any rate although a straightforward search algorithm might be the easiest way to get at least middling results I'm sure it collapses if you want to try and get at truly great long term behavior. Just like most games the tetris search tree is definitely exponential and if you really want to be a good tetris player you have to shape your pieces in ways that are conducive to future building. For even mediocre it would be desirable to be able to look ahead 3 moves at least since you need at least 3 pieces to fill a line to clear.

For the moment lets consider the branching factor of tetris. For a long white piece there are 2 possible rotational positions and 10 possible horizontal positions for one rotational configuration and 7 horizontal positions for the other. giving at least 17 different possible positions for a long piece. For each of the 2 L shaped pieces all 4 rotational positions are different from each other and there are 9 horizontal positions for 2 of the 4 rotational configurations and 8 horizontal positions for the other 2. So each of the L shapes has at least 34 possible placements. The T shape has a similar analysis and has at least 34 placements as well, and so do both of the S pieces. Finally the square has only 1 unique rotational configuration and has 9 possible horizontal positions and so has 9 possible placements.

So we get a branching factor of 34^5*17*9 = 6951619872

So from a straightforward perspective as a search problem tetris is much much much more difficult than say chess which has a branching factor of somewhere around 35 or so (or actually 35^2 since each player has about 35 degrees of freedom on average). So why is it that chess is hard to play and tetris easy? the answer is that in chess most of the time only 3 or 4 of those 35 moves is any good whereas in tetris most of the time no matter how bad a move is the game can be salvaged. So in chess there are a few good paths to winning which are very difficult to find and in tetris there are a vast number of good solutions. Relatedly the reward schedule is much shorter in tetris than in chess. A good move will be rewarded and a bad move punished generally in a much shorter number of steps in tetris than in chess making it easier to discern what moves were good and what moves were bad.

This reminds me of the n-queens problem. The n-queens problem is where you try to position n queens on an n by n chess board so that none of the queens has any other queen on its lines of attack. Solving the n-queens problem can be fairly complex but actually the application of greedy search with a good heuristic and a random starting point is pretty likely to give you a solution. The reason is that the solutions of the n-queens problem are "dense" in the space of all possible n-queens board positions. If you start at any random board position it is pretty decently likely that there is a solution board position fairly close by in the state space.

I think tetris is kind of like a simpler version of go which isn't adversarial (another reason chess is harder than tetris) Perhaps a good intermediate challenge for the AI community before we get a computerized go world class player would be to get a world class tetris player.

Monday, August 3, 2009

I'm Graduating

So there is a requirement for the mathematics degree that says that you have to take the mathematics subject GRE and get better than the 9th percentile. Now while this doesn't seem like much of a barrier there is one little problem. I thought the subject GRE's like the genergal GRE was given all the time and any time I wanted to I could go and fulfill this teeny little requirement. The problem was that in fact the subject GRE's are administered only about 3 times a year... And you have to sign up for them waaaay in advance. So I thought that my bad planning had made it impossible for me to graduate this past spring. However... I was wrong. I went and talked to the appropriate people (finally) this summer and it turns out that the GRE requirement has been changed so that I can replace it with one extra elective course... which I had already in fact taken for fun.... So... that made me feel kinda stupid. The whole not even checking if I could graduate thing.

So now after jumping through the appropriate hoops it looks like they are going to let me graduate summer semester even though I am applying only 4 days before the end of the semester and even though I still don't have my AP results to them after 5 years. Speaking of which that is the biggest headache of all. I still have to wait for a week or more before they will even send the scores and then I have to go back to the school to sign a little piece of paper that says I want them to release my scores and I have to make sure that I talk to some person named jason in order to get them on my transcript for the semester that I want them. /headache

but as I was saying, the bright side is that I am getting my degrees, I will shortly be the proud new owner of a Physics B.S. a Mathematics B.S. and a CS Minor.