A recurring theme in physics is that of an extremum problem.  Extremal configurations are ubiquitous in nature.  A black hole is spherical because that is a surface of minimum potential.  A black hole also possesses the maximum amount of entropy possible in that region of spacetime.  If something disturbs the black hole, it will undergo a transient stage in which its relevant parameters are neither min nor max, but will readily settle back down into an equilibrium position that is a min/max.  It is therefore not surprising that many of the laws of physics can be formulated in terms of minimum principles.

The Principle of Least Time, originally due to Fermat, is such a principle, but it is incomplete in that the more general formulation requires that the optical path length must be stationary, meaning that there can be situations where light takes an extremal path other than a minimum.  That calculus talk is all fine and dandy provided you have a good numerical feel for what it means to analyze a stationary point.  Feynman encourages us to take such a stand…
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Project Tuva hopes to introduce physics to the masses through entertaining lectures à la Feynman.  Thrilled with the first lecture, I encouraged my busy girlfriend to take time over the weekend to watch the second lecture with me.  Judging purely by her reaction to “The Relation of Mathematics and Physics,” Bill Gate’s efforts are not efficacious.  But it’s too soon to write him a reimbursement check, as she falls asleep anytime we curl up to watch something on the couch.  I, on the other hand, was completely engaged with this lecture, as was the original crowd it seemed.  My favorite joke was in there, probably in its original form.  These days it’s told as, A physicist seeks out a brilliant mathematician and asks, ” how do you visualize four-dimensional space?”  The mathematician responds, “Well, first I visualize n-dimensions, and then I set n equal to four.” If I tell it just right, that can actually get a laugh out of my girlfriend.  Since she is a math PhD student, by the way, I thought it appropriate to assign gender when contrasting mathematicians and physicists in what follows.

Feynman stresses that the physicist needs to assign physical meaning to the equations, whereas the mathematician can just keep hammering away with a rigorous approach to everything.  He in essence says that the two attack a given problem in completely different ways, albeit work with the same mathematical machinery.  When researching something new, the physicist need not bother with organizing his thoughts in a coherent framework that can then methodically be applied to gradually get to the heart of the problem.  Rather, he let’s his intuition do that, and relies on conservation laws and simple models to try to get a grip on the problem, letting it simmer in his head for weeks or months on end, until finally one day, insight gleams forth under some relaxing state of mind, and everything falls together.  The mathematician, meanwhile, works hard to put everything in place before she ever begins.  She likes her problems well-posed, for then she can reach into her bag organized case of tools and bring her training to bear on the problem in a straightforward manner, deriving the result, establishing convergence, proving uniqueness, etc.  That process certainly requires ingenuity and sometimes strokes of genius, but it follows one after the other in a laid out procedure.

The physicist follows a different line of attack.  His mind is quite cluttered.  I would compare him to a curious craftsman trying to open up a black box, unaware of what tool he might need next.  He doesn’t have the luxury of an organized workspace; he must keep all of his tools at his fingertips.  Sure, he possesses a deep understanding of mathematics.  Otherwise, it’s unlikely he could ever forge connections among similar concepts in physics, let alone among the vast fields of physics, that are crucial to making significant progress.  But he doesn’t concern himself with the likes of real analysis past a certain stage of utility.

I sort of like my black box analogy because it captures, if only in a highly simplified and over-generalized way, the interplay of these two fields.  The boxes are the problems from physics, and the tools to open them are mathematics.  History has shown that after opening one black box, the physicist is presented with another inside, as if he had just opened a Russian nested doll.  Excited, he gets to work on trying to open the next black box, while the mathematician often occupies herself with polishing up the one he just opened.  Or she might be developing a tool which he needs to open the next box, yet neither has any clue that such is the case at that point.   Occasionally the tools to open the box have been around for many years but the physicist has not learned to use them.  And certainly many a mathematician take a stab at opening the boxes themselves, more often than not only to pry it open part way until one day a physicist comes along and shakes it up and down, pours out all of its contents, and leaves it swinging from its hinges.

It used to be that mathematicians took all of their problems from physicists for the most part.  However, now that math is infiltrating other fields at an overwhelming pace, mathematicians are beginning to learn less and less about physics.  Yet the reverse is not true, while the concepts of physics are also finding numerous applications in other areas.  It remains to be seen what will come of all of this, but I can say that being in a relationship with a mathematician has only heightened my respect for them overall, as the skill set they develop truly is unique.

Inspired by Sean’s post a few days ago about the release of Feynman’s Lectures on the Character of Physical Law, I felt compelled to share my first time encountering the Feynman Lectures.  I don’t recall learning of Richard Feynman in high school, and that is probably not uncommon, as the names Einstein and Hawking dominate at that age.  My first exposure was in my second semester in college, when I took my first college physics class, “Light”, which covered basic optics and special relativity.  The instructor was an adjunct from Caltech and would print us relevant chapters from Feynman’s Lectures.  Fast forward to the following winter, after taking an introductory E/M course and firmly committing myself to a major in physics, when I sat down to read Six Not So Easy Pieces, which are the six chapters covering vectors, symmetry in physical laws, relativity, and curved spacetime—the more engaging topics from Feynman’s first volume of lectures.

A typical setting for digesting thought-provoking material is not the front seat of a Pontiac in the midnight to early morning hours at below freezing temperatures.  It was the last week of December in 2003, and the country was on Orange Alert, which had prompted a massive deployment of security guards at spots thought to be at high-risk for a terrorist attack all throughout the US.  I had signed up for a graveyard shift guarding one of the city’s main water towers to make some quick cash.   Aside from turning my engine on for a five-minute perimeter-check every hour, I was to stay parked in a dirt lot overlooking the tower for my entire eight-hour shift, making sure I radio in every 20 minutes to let them know I am still awake.  My friends called this a most unbearable job description.  I thought it was better than a minimum duty work-study job at a library.

Clutching a flashlight in order to read Feynman’s words in the blackness around me, it slipped my mind that I was still cold with three layers of clothing on top of thermal underwear.  Captivated by his coherent account of the field I hoped to dedicate my life to, I took in his sense of wonder and admiration for our ability to really understand.  I would periodically glance around in bemusement at the phenomena around me, such as the subtle green glow emanating from the LED of my walkie talkie, which was neatly spread about on the frozen precipitation of my windshield.  I was looking out into the night sky pondering General Relativity, confident that with Feynman guiding me through the language of nature, I could grasp its deepest secrets.  It was an enlightening experience, a crossroad between boyhood wonder and sophisticated thinking, one that I look back on when I am in need of comfort for pursuing (as a first choice) a career with dim prospects for employment.

Every field has its heros.  The nice thing about making Feynman one is that he is not nearly as mythical in the popular press as Einstein, yet he was certainly a cut above the rest.  I agree with Julianne’s take on Feynman, though I had no qualms about worshiping him as an undergrad.  Feynman worship in graduate school should be minimized, as that is setting yourself up for failure (or for revitalizing Wal Street).  However, his lectures should continue to be utilized, as they are brilliant.

Anytime that light hits a medium with a different index of refraction, some is reflected and some is transmitted inside and refracted.  For a given angle of incidence, we quantify the angle of reflection and refraction.  The former is easy: angle in equals angle out, but the latter is more tricky—it’s given by Snell’s Law.  It so happens that we get both of these ‘laws’ due to a beautifully simple property of light, that it obeys the principle of least time.   As light travels from one medium to the next, it takes a path that minimizes the time of travel.  For the case of reflection off of an interface, assuming light remains in the same medium the whole time, that light takes the path of least time is equivalent to it taking the path of least distance, since d=vt and v is the same before and after reflection.

Feynman’s description of the problem poses a method of brute force attack.  First, his excerpt:
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In graduate level special topics classes in physics and math, professors often pick and choose material from several different texts and research papers of interest.  You might find that they just xerox their own copies of the articles, which often tend to have scribbles all over them.  This is indicative of active reading.  Professors don’t just curl up on the couch with a research article in the same way they might with a novel.  As a matter of habit, they follow the argument presented by the author with a pencil in hand, filling in any skipped steps in the calculations.  The benefits of mimicking this practice of marginal notes seemed, well, marginal, until I began teaching and could fully appreciate how much this aids in my understanding.

As I am reviewing basics physics by reading through some chapters in the Feynman Lectures,  I often feel compelled to take this one step further.  Feynman was a brilliant theorist who could have easily confounded readers by lecturing at a mathematically over-sophisticated level, but rather he describes his subject in a very applied, intuitive manner.  His lectures are strewn thick with what I call “numerical nuggets”, indicating his ability to perform numerical analysis in his head, if only at qualitative level.  You can tell that he arrives at an analytic expression using calculus only after he deeply ponders the limiting process underlying it.  To fully benefit from Feynman’s insight, therefore, I am attempting to quantify some examples of this.

Since FLoP is an acronym for the Feynman Lectures on Physics with an appropriate numerical pun, it makes for a good title, I think.  And it certainly describes my blogging effort overall as viewed by my girlfriend, who deems it an utter failure.  In any case, it provides me additional motivation to not review college physics passively and at the same time keep up with my coding skills.
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The fifth summer school for Gravitational Wave Astronomy (GWA) wrapped up a month ago on South Padre Island, a popular Spring break island resort spot on the Texas border near Mexico.  The Brownsville Herald quoted Peter Saulson as saying that the 2-week program is “the only way to learn the basics of this new scientific field of gravitational wave detection.”  If you haven’t heard of Dr. Saulson, he is a big name on the experimental side of GWA.  His PhD adviser was David Wilkinson of WMAP fame (and he was the esteemed colleague of Cosmic Variance’s Mark Trodden before Mark left for Penn).  He is a fantastic lecturer, one of four that the NASA-funded Center of Gravitational Wave Astronomy has hired to run the summer school.

End of Week 1

End of Week 1 Group Photo

I attended the program last year and would summarize it as the single most memorable experience pertaining to physics that I have ever had.  The group of students in attendance were top-caliber, and I made friends with almost all of them, some of whom I still keep in touch with on facebook.  Lots of them were already involved with GWA in one way or another, a couple having internships lined up at LIGO and a couple more doing research for their advisers on data analysis or numerical relativity.
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There was a scene in the movie Hackers in which (according to wiki) “the characters Razor and Blade briefly explain how to manipulate payphones to make free calls.”  I have no clue about the validity of that, but I do recall them having a cassette recording of the dial tones for their call.  From the creator of MATLAB himself, Cleve Moler, in his free online book, here is one way to generate the tones for that recording.

8.1 Touch-Tone Dialing
Touch-tone telephone dialing is an example of everyday use of Fourier analysis. The
basis for touch-tone dialing is the Dual Tone Multi-Frequency (DTMF) system. The
program touchtone demonstrates how DTMF tones are generated and decoded.
The telephone dialing pad acts as a 4-by-3 matrix (Figure 8.1). Associated with
each row and column is a frequency. These basic frequencies are
fr = [697 770 852 941];
fc = [1209 1336 1477];

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On more than one occasion, I’ve heard some professors refer to MATLAB as “just a toy.”  Surely they are not dismissing it as simply a portal for students to learn programming, as it is widely used in academic research as well as in industry.  What I hope think they mean is that MATLAB is a superb exploratory environment that falls short when it comes to speed and efficiency compared to say Fortran or C++.  In memory-intensive computer programs coded with a formal programming language, MATLAB can provide an accuracy check on various portions of the code, assess the feasibility of a given algorithm, or study the relative merits of a certain computational approach.  It can serve as an excellent preliminary measure used to gain insight into the dynamics of a problem before diving in and creating an efficient program.  Or it can be used in post-processing for visualization purposes.    All in all, it is a very powerful tool, the result of three decades of intellectual outpouring by  thousands of scientists and mathematicians.  And that is probably another reason for professors calling it a toy.  The script they write will generally depend on built-in functions (otherwise they’d just code it in Fortran or C++) , and this might hinder the debugging process and complicate publishing rights.

The built-in functions in my opinion make MATLAB a weapon, not a toy.  They are what prompted me to start this blog, as they render accessible a playground on which to extend my imagination, to carry out on a computer screen the phenomena I try to visualize in my head.  They compensate for the time-constraints of a PhD student who would otherwise not have the time to write the necessary code for manipulating data structures that is done with ease in MATLAB.  As processors keep getting faster and faster, speed is becoming less of an issue.  At least in applied mathematics and signal processing applications,  MATLAB is frequently used as the primary computing platform, even in publications.  My guess is that MATLAB will only gain momentum as a means for both teaching and doing physics in the coming years and I hope to stay abreast of the developments.  Hablas MATLAB?

Since “Hello World” is the title of a 1st post on WordPress by default, I might as well keep it, as it is apropos to a blog that will feature a programming language.

As has become customary in getting started with any program, here goes the appropriate command line in MATLAB:

disp('Hello World!')

…it doesn’t get more simple than that.

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