# Content tagged Physics

Bill Nye to Visit Creation Museum for Debate - ABC News
posted on 2014-01-04 01:46:27
Multiple Cursor Mode
posted on 2013-09-26 15:35:00
In case you haven't already tried it, Multiple Cursor Mode for emacs is awesome. I actually got chills the first time I used it to edit multiples lines of work on a physics problem. All those repeated lines of LaTeX code, and now I can change them all at once!

It's in Marmalade, so go try it out!
My First Appearence in the Media
posted on 2013-03-16 21:41:50
A friend sent me a link today to something I took part in and had nearly forgotten about.  Nearly two years ago, my undergraduate adviser Kiko Galvez invited me back to Colgate because he had two people from Scientific American coming to make a short film about quantum entanglement, which we studied in the lab there.  They finally published that video today on their website.

I'm in the video only when they come to Colgate, where they shot Kiko and I shaking their hands and saying hello.  I'm nowhere near the educator and scientist that Kiko is yet, so I didn't manage to say anything as clearly as he did, and I seem to have ended up on the editing room floor, as they say.  Despite that, it's my experimental setup that I built and debugged that gets showed off, although it's set up with a nicer laser than I got to use.

If you're interested in entanglement and quantum physics, give it a watch.  Kiko's great at explaining things, and does a wonderful job in the video!
Science as told by comedians
posted on 2013-02-22 20:37:08
Lately, I've had the good luck to find a number of science shows trying to bring modern research and understanding to a wider public than the scientific communities.  I've been suffering through a long dearth of employment that I'd like to write about as soon as I understand it better myself.  Yesterday, I went on a search for new podcasts to fill my copious free time and found this! It's sort of in the same vein as Dara O'Brien's Science Club, and Neil DeGrasse Tyson's Star Talk.  Like Science Club, it's out of Britain, but has a tone more like Star Talk.

The format that all of these shows have in common is that some scientists and comedians try to make science more accessible and present. Billy Bragg, a legendary British punk who wrote many songs about labor movements and sexual politics, was in an episode I just listened to, which was exciting for me, as a fan of his music.  Unfortunately, part of his contribution to the episode was making the science as a type of faith argument, which I find very dull and not at all worthwhile.  That said, I hope to sort my feelings on that out into words sometime soon and put it up here.  Some of the episodes of these shows are naturally better than others, and I am grateful to the astronauts and scientists who take the time to go on them and be excited about their present work.  Getting to hear the cutting edge of science from the people who do it makes it all the more real.

Map Take 2: The Slicening
posted on 2012-11-30 22:05:50

It's been a while since I wrote about my scientific computing library for lisp: map.  Map is a great exercise for me -- in learning Lisp and learning algorithms and optimization.  Since I'm between jobs and not yet in grad school, the time has been ripe to work on the library with some toy cases and try to make it as usable as possible by the time I get back in a position where I could use it for real work.

Because of my copious free time, a lot has been changing lately, including the addition of matrix slices, which were important, and such important features as matrix inversion.  I'm also looking at adding parallelization at some point, as well as a matrix-defining macro in the style of the #v() one for vectors.

In any event, here's what's new:

Reflections on a year of Job-Hunting
posted on 2012-11-15 21:28:49
The past year has been one of unending frustration and despair.  I've had jobs, sometimes even jobs in Physics, which is my favorite kind of job, but even those have paid little, been short-term only, and sometimes been in very unwelcoming environments. I feel a lot of anger and frustration, because I feel like a lot of people misled me.  I don't think they did it on purpose, and I think a lot of it is disconnection with some parts of life both on my part and the parts of others.  I think my professors didn't know what sort of world they were sending me into, and I think they generally assumed either that my classmates and I wouldn't be continuing with Physics, or that we would be going right to graduate school.

I do think many of my classmates jumped off the Physics ship as soon as they got done with college.  But I know I've felt rather lost in the last year, which feels like it has been far longer, with some significant help from my research adviser, Kiko Galvez, in terms of names to talk to and introductions, but by and large, the year feels like a random walk experiment.

Map
posted on 2012-08-22 21:26:44

For a while now, I've wanted to make some of the great functionality of things like Octave (and it's parent Matlab) to Common Lisp.  Mostly, I want things like the slice assignments (arrays with ranges in the indices) and matrix math.  Also, it never hurts to make higher mathematical functions available in simple ways.  So, I started writing Map, which I hope will do just that.

Lately, I've been working in singular optics, largely with Spatial Light Modulators, which are like very tiny LCD screens in front of a mirror. They're cool because they can transform the wavefront of a laser beam into any sort of beam you'd like!  We use a fair bit of math to pump out the right images to put onto the SLM, and I'd been wanting to make a more general interface for that for a while.  I'm not there yet, but I'd like to share the few things I've done so far.

## Vectors

In Octave, you can type

[1:10]
and it will automatically be expanded to
[1 2 3 4 5 6 7 8 9 10]
.  This is great notation and can be used both for generating a vector or setting a range.  In map, I've implemented those with
#r(1 10)
, which creates a 'range' class that just keeps track of the numbers, and #v(1 10), which will expand to
#(1 2 3 4 5 6 7 8 9 10)
, like the Octave code.  This means you can do things like
(reduce #'+ #v(1 100))

To add up the numbers 1 to 100.  That, of course, isn't hard, especially when Gauss came up with a much easier way, but you get the picture.

One further thing that's special, is that you can apply a function to the vector you're generating by passing another argument (you can also pass a step size by entering three numbers).

(reduce #' #v(1 .1 10 #'sin))

will give you the sum of the sine of the numbers 1, 1.1, ..., 9.9, 10!  Moving on...

## Differential Equations

This is a much more meaty section, and was really fun for me, since I hadn't really implemented a ODE solver before (that I remember).  Map now contains a Runge-Kutta Feldberg 45 solver, which is supposed to have an adaptive step size, and currently doesn't seem to, so I didn't do everything right, but it works to a certain accuracy.

Here's a demonstration of finding the angular position and velocity ($\theta, \omega$) of a damped, driven pendulum, taken from some of my old computational physics notes.

(defun damped-pendulum (ti yi)        (declare (type double-float ti)                 (type (array double-float 2))                 (ignore ti))        (vector (+ (* -1d0 (sin (elt yi 1))) (* -1d0 .5d0 (elt yi 0)))                (elt yi 0)))
(map::mute (multiple-value-setq (ts ys)         (map:rkf45 #'damped-driven-pendulum                #r(0d0 1d-7 4d1)            #(0d0 1d0) 1d-10)))

Now, ts holds the time values, and ys is a 2x(length ts) array of position and velocity values!  Once I implement array slices, it'll be easy to graph them, but for now, you need to manually extract one of the rows of ys to plot against ts. There's still a lot of work to be done. Anyway, the resulting graphs are:

Thanks for reading, I'll probably post more once I've got slices sorted out.

In with the out crowd
posted on 2012-07-13 16:39:31
I was skimming through Planet Fedora today, and came across a post by Mairin Duffy, one of the designers at Red Hat. She was writing about a conference called Ada Camp, which exists to support women in the IT industry especially in open-source software.  I always jump on these sorts of posts because I care about equality in life and, not being a woman, I don't get to have (maybe even can't have) the sorts of conversations that happen at these things.  I was, therefore, very interested in what she and the other women had to say.  While I'm more of an enthusiastic onlooker (and user) to Open Source, I believe there are parallels to any other field where women (or any other group) are a minority, such as my beloved physics.
D-Wave's Lightswitch Game
posted on 2012-03-03 18:35:25

Suzanne Gildert is a scientist at D-Wave, which claims[1] to have created the first quantum computer. They currently have sold one to Lockheed Martin, and at least rent time on one to Google, even though the scientific community doesn't know if they're really selling a quantum computer or not.

One of the reasons that all of the scientists have such trouble saying whether what their machine does is quantum computing or not is because their computer could be doing either one of two different things, and getting very similar results.  They are either performing Quantum Annealing or Simulated Annealing which are very similar techniques, and there is certainly no reason their computer shouldn't work regardless of what they're doing, and will be quite good at solving any problem that can be expressed by the equation $$U = \sum_i h_i S_i - \sum_{<i,j>}J_{ij}S_i S_j, \quad (1)$$

which are much more numerous than you might think[2]. The big prize at stake, though, is being able to claim that you made the first reuseable quantum computer, which is naturally a huge claim to fame in the realm of quantum computing research.

Both quantum and simulated annealing work by minimizing Eq. 1, in which all of the $$S_n$$'s represent what physicists like to call "two-level systems."  That is, something with two main states -- eg. spin, which is up or down or polarization which can be reduced to being horizontal or perpendicular to a plane -- which can form a quantum equivalent to the binary 1 and 0 we're all used to now.

In annealing, the overall group of two-state systems will have different amounts of energy when some of the parts are in different states. So the equation will be minimized when the parts are in the correct combination of 1's or 0's.  Suzanne wrote up a nice blog post about that for D-Wave, so I'll just send you off to that.

The important difference between quantum and simulated annealing lies in how the group of objects goes from a starting state, say all spins pointing down (we'll call it 111 in binary) to whatever the lowest energy state is.  In the picture, I made up a system where the x-axis shows three two-state systems and what state they are in (i.e. '010' means particle one is up, particle two is down, and particle three is up) and the y-axis is the energy of the group of three in that state.  As is common, we start in state 111, at the very rightmost point of the graph.  In both cases we hope the system will end in 100, the lowest energy state (See? It's the lowest point on the graph).

## Quantum Annealing

In quantum annealing, we use the phenomenon called quantum tunnelling. Tunnelling is the quantum property by which a system can move from a low energy state to a lower energy state by skipping over an intermediate, higher-energy state.  In macroscopic terms, it would be like a ball on the ground next to a well suddenly being inside the well.  We don't expect it to end up in the well because it would need to raise itself up the side of the well first, something which would take energy to do, and since the ball was just sitting there, nicely, we wouldn't expect that at all.  Quantum objects do this all the time and the effects just don't add up to much on the scale of our ball.  Nevertheless, there's a calculable probability that all of the atoms in the sun will jump simultaneously to right where Earth is, but it's so small that its chances of happening before the universe ceases to exist are on the order of you winning the lottery a few times while getting hit by lightning and dying in plane crash simultaneously (please don't check that statement mathematically).

In the quantum world, we can take that graph and turn it upside down in our heads.  Now we're imagining a sort of probability distribution representation of the system.  The quantum way of thinking about it is that if we measure the state of the three particles over and over, we'll find them in state 100 most of the time, because that is the loest energy state, but then we'll also find it in states 011 and 111 sometimes, since they're more energetic than 100, but not by much and so are the next most likely states.

This method is dependent on maintaining coherence among the particles -- a special quantum property where the properties of the particles are interrelated.  One of the hallmark measurements of quantum computing is the coherence time of the qubits, which determines how long you have to do quantum-style work with them before they turn back into regular old pumpkin particles.  This is one of the big criticisms of D-Wave -- they haven't published these numbers, and so nobody can say for certain that they're doing quantum annealing as opposed to, say...

## Simulated Annealing

Which is not quantum at all!  Simulated annealing serves the same purpose, though, and, by analogy, uses a balloon instead of a ball, and hopes it deflates over the well and falls in.  In this case, the system is exposed to some energy, so it can travel up and down the slopes of the graph as it likes, and is slowly cooled (or some equivalent, energy-removing operation) in the hope that, as it cools, it will fall into that low energy state.

### Behind Closed Doors Does Not a Community Make

While I certainly don't like the method of keeping all of your cool research to yourself, I do think that D-Wave is doing cool research.  That said, I think their marketing department is probably stretching the truth if not outright lying about what they actually are selling.  As I was attempting to say, though, simulated annealing will get the job done in any event, I think most academics are just upset they're building something even remotely quantum while most of the rest of us are spending hours adjust delicate equipment in labs, trying to get a handful of qubits to do anything while they're claiming hundreds.  If you're interested in some of the controversy, you can spend a while reading Scott Aaronson's very interesting blog.

[1] D-Wave only publishes select information to the scientific community at large, and, as of the last time I really looked into it (a few months ago), they hadn't published anything that anyone had taken as definite results.
[2] Google seems to be using this for training image recognition software.

Maxwell's Sheep
posted on 2012-01-31 17:26:17

In the late 1700s, James Maxwell came up with a dilemma that, although just meant as a though experiment, was a troublesome idea to physicists.  He came up with a clever arrangement of systems of matter at different temperatures that might possibly violate the second law of thermodynamics, which would be troubling because, well, it's supposed to be a law, and we don't like nature going around breaking its own laws, since when that happens, it means we got the law wrong in the first place.

The experiment is as follows:

1. We have two systems of different temperatures that are isolated from each other and any other system they could exchange heat with.  Since the energy has nowhere to go, they will remain at this state. (This is in accordance with the first law)
2. We bring the two systems into contact and have a small door, guarded by a small demon, which only allows heat to flow one direction. That is, the demon checks if a particle moving from one system to the other is one of the 'hot' particles and allows it to move through in one direction on that condition.

Here we have to stop a minute and realize, as many did after him, that the situation where this demon requires no energy to do its census and rearranging of every molecule in the systems is impossible.  Measuring the particles requires interacting with them, and so the demon itself is part of the large system here and the energy it uses sorting is part of the overall equation.  This is where my experiment today is different!

I am performing this demonstration in Minecraft, which is a made up world that very clearly marches to the beat of a different Grand Unified Theory, and so I can create a zero-entropy demon.  My demon will be played by a fence gate and a pressure plate.

Here we can see a set of two sheep pens with my wonderfully rainbow-colored sheep in them.  All but the red sheep are in pen two (the further pen) representing a system at higher energy than pen one (the nearer), where there is just one sheep.  In the Middle is the gate with a pressure plate which will cause the gate to open located on the side of higher energy (read: more sheep).  This means that energy (sheep) can only flow from the higher energy to the lower energy pen1. This may seem obvious, but it's also the situation Maxwell tried to set up in his famous experiment.

Let's see what happens!

Long story short, it worked! I left the sheep alone for a little while, as the time of day change demonstrates nicely, and when I returned they were all stuck in the near pen. In case it was in any doubt, this says some strange things about the state of entropy in Minecraft. Perhaps things like cheap cold fusion are easy in this world. Maybe I just need to wait for a hydrogen block and a deuterium block...

[1] I have chosen to ignore second-order sheep effects, like a sheep stepping on the plate and allowing another sheep from the lower energy side to pass back into the higher energy side.

New job again!
posted on 2011-09-11 17:13:48

Well, the summer ended and it was finally time to move out of central New York. I managed a whole two weeks of work at the Air Force, but met some nice people. Now, though, I am relocating!

When looking for an apartment in New York City, there is a strange dance to be done. First, one would want an apartment, right? I sure did. Apparently, though, you need to be able to prove you can pay for it before you can move in (if you can find one at all) which means you need a job before you can rent an apartment. Of course, it would be nice to live near that job in the city that you're paying for the apartment with, wouldn't it? You can't do that until you have the job. I don't know how most people deal with this. After a few weeks job and apartment hunting, I'm guessing a lot of people just don't.

In any event, I got a job with the Wong Group at Columbia University.  This is quite new to me!  At this point, most every new job is a completely new experience for me, but in this case, well, this is probably my first real job.  I worked in a public library for 2 years, so, I guess that probably counts as a real job, too, but that was during high school and this is in a field I studied in College.

On my first day of work (Wednesday) I was given a budget code, told to order what I needed and left to do what I would in the lab with a laser that cost a quarter of a million dollars.

Then, I reminded myself that I was, in fact, qualified to use the equipment and got about learning how the particular equipment that they use in this lab works.  It's certainly a very free-form environment, working at a University instead of a government lab.  People are in and out whenever, and my introduction to the equipment took place at 8:30PM.

As usual, I've gotten myself into an unusual situation.  I'm working in the Mechanical Engineering department, where they're big on building things, and people at talks get their degrees listed along with what companies they've started.  I have yet to understand a talk given by another person in my lab (and I've already seen a few) so I'm hoping I can return the favor in a few weeks when it's my turn.

I'm working on checking some of the devices they work on.  Right now, I'm just checking some bulk BBO crystal to make sure it's creating the right entangled state (the $$|\Psi^+\rangle = \frac{1}{\sqrt{2}}\left(|HV\rangle + |VH\rangle\right)$$ state), by quantum state tomography.  Apparently, the group is (in part) working on entangled photon sources on a chip, and so once I've shown I can do QST, I'll be doing it to the outputs of a fiber and chip based device!

Wir tauschen Zeit für Geld (und hoffen lass mich jetzt nur so weit sein)
posted on 2011-06-16 02:27:10
Man, I've had a blog for how many months and haven't included a song in a title in some way?  These first two weeks have been my introduction to the life of a working physicist -- specifically a government-employed physicist.  Even more specifically, as I found out today, most of whose co-workers are computer scientists.

The lessons I learned today are two-fold: Never go to a set of 5-minute talks.  You will not remember anyone who spoke (ok, maybe one or two) and 5 minutes of talking means nobody gets to explain anything.  Also, they will go over 5 minutes trying, but still not really manage to talk about much, and you won't want to listen because of all of the other talks lined up after them.  Those were some of the dullest 4 hours I have lived through, my friends.  Wow.

On the brighter side, I am doing work now!  It's a lot nicer than sitting in a cubicle all day doing nothing.  Now I read books and articles, and try and make octave do math.  I'm even getting plausible numbers!  Today, I also experienced my first research group meeting, which was new and neat.  Getting a bunch of people together who are working on a common project and hearing ideas, suggestions, etc, was rather exciting, and certainly made me feel more a part of something.  I think a lot of people come in and out of the group, so people don't really go hugely out of their way to welcome newcomers, which makes sense, but didn't make me feel very at home very quickly.

That said, everyone's very friendly and accessible, and it's fun learning new personalities and seeing how they interact.  Unfortunately, I don't think I'll be writing much about my day to day research, as sharing what I'm doing is discouraged, but I'm already looking for the next thing to do and I'll make sure there are no problems sharing it.  That's what science is about, after all.
Working for the Gub'ment
posted on 2011-06-06 22:36:07
Well, now I'm out of school, and the tradition is to find a job. One way or another I ended up with a job and now, much to my surprise, I'm working for the air force. This also makes for the first time I've moved somewhere for a reason other than to take a class. I've been to Germany, to Rhode Island, and Hamilton, but they were all for school reasons, now I'm in Utica for work.

It's been pretty strange moving into a city all alone. I only managed to find an apartment here two days before I moved in, and I was pretty lucky for that. That said, I'll probably have a roommate soon, which will be a little different. Especially since I don't get to choose who. The apartment feels sort of middle of nowhere, although I'm pretty close to the Matt's Brewery, not that that means I get free beer or anything. It's hard to express, though, how strange being here alone is. I'm very glad I know some people nearby, and that my friend Dan was able to come up yesterday. The first night was pretty lonely. There are so many new places to learn, grocery stores to find, neighbors to meet or become comfortable with not seeing, parking arrangements to sort out.

So far, the job hasn't been great either. I had my first day today, and felt like I got nothing done. I wasn't expecting much, but today was something especially dull. I spent all day trying to get my security badge, but was behind other people in line until late in the day, when everyone who could sign my forms had, apparently, gnone home. So, I needed to have people escort me all over the building, because I wasn't allowed to be un-chaperoned. I even needed someone to walk me to the bathroom.

That aside, I'll be glad to be doing some research work, and look forward to meeting more of the people, because so far, the scientists have been exceedingly nice.

My First Magnetism Lesson
posted on 2011-04-24 22:51:30
So, I'm taking a class on science and math education this semester because I think they're important things for people to know, because so much of our modern world depends on them, and they often run so counter to our intuition.  Even as someone who has been taking physics courses for the last six years, I often find myself not completely sure of how things work, or at least unable to explain them to people when the chance arises.  For this class, I've been visiting a local high school and sitting in on their physics class.  I get to help out a little, and I'm slowly learning a bit about the craft of teaching.  While the part I'm most afraid of is classroom management (Not necessarily the best and handling conflict) I can only learn that from experience, and to get experience I have to plan some lessons...

Rochester Symposium
posted on 2011-04-24 22:15:24

I'm already two weeks late on this (and less late on other things) but two weeks ago I got the chance to present my senior research at the University of Rochester.  For those who haven't already read about it, I've been working on quantum optics with professor Kiko Galvez at Colgate.  I got to start working on this back in September, and being only a senior in college, I can say with little doubt this is the subject I know the most about in physics.  Since then, I've become attached to the subject, and was really excited to get to talk about it in front of an audience.  Furthermore, since the conference was titled the Rochester Symposium for Physics (Astronomy & Optics) Students (emphasis mine), I figured I'd probably be talking to an audience that knew something about what I was talking about.

This is how the world begins, not with a bang, but with a... collision of multi-dimensional manifolds.
posted on 2011-03-23 05:59:11
The Physics and Astronomy department at Colgate hosts weekly lectures by professors from other institutions about their research or interests.  This week we had the pleasure of hosting Professor Adam Frank of the University of Rochester, who studies stellar outflows, and how they affect start formation.  I was really surprised to learn that was what Professor Frank studies, because his talk today was about cultural perceptions of time.  He has, in fact, written a book about this (which isn't yet published, so here's a link to another one of his).

While he has obviously read a lot about the subject, and taught me a few things (e.g. first sleep), I was most interested in the talk we had afterwards over lunch with the physics club and professor Bary who also joined in.  The discussion went about the idea of energy sustainability, mostly, and how oil has given us a 'free energy' card to play for the last hundred years that allowed us to live in ways that we probably couldn't have otherwise.  This notion of a free oil energy card was new and unusual to me.  It was based on the extreme energy-freedom we have now because of all of the energy we use from oil.

Oil is (like most earthly energy sources) mainly stored solar energy, in a potent form.  Over millions of years, plant and animal matter has been pressed down into the stuff and collected in pockets in the Earth.  Because we only found out about how much energy it had recently, we've had millennia's worth of energy to draw on, and we've drawn most of it in the last hundred years.  This allows us the cars we're all so used to, the sprawl, the easy consumption, but imagine a world with a lower energy budget.  What if we could only afford to run the washer once a month? Or to drive only on the longest of trips because the energy to power these things was so rare that we actually only had enough to use it sometimes. I'm pretty sure I can barely even conceive of that

Also discussed was the failings of modern string theory to explain the so-called fine-tuning of the standard model.  The fine-tuning problem is that there are a number of constants in the standard model describing forces and the like that just seem to be from the universe itself.  We don't really have any reason they should be what they are, other than that they make the equations describe our universe.  The other strange part is that they could only be pretty much exactly what they are to get anything like our universe to exist.  Some people like to use this sort of thing as a rationale for a god of some kind, but that's just not seeing the pavement for the puddle.

Boxcar2d
posted on 2011-02-13 23:09:09

In the last few days, I've spent a lot of time zoning out and watching this play. It uses genetic algorithms to design cars out of combinations of wheels and vertices. For the first few generations, it's usually pretty stupid, and then gets a lot better as time goes on. Really fun to watch in any event. The website is here.

Dawn of a New Semester
posted on 2011-01-13 06:48:47

It's now officially Thursday, which means there are only 3 more days before the new semester starts.  If all goes according to plan, I'll be taking Intro to Quantum, a class on teaching math, and a German theatre/plays course.  My fourth course slot will be filled by independent research, because I got asked if I would like to try for honors in physics, and I certainly would!

Things exploding
posted on 2010-09-02 02:07:00

Back in America and classes are starting again. While I've definitely learned to better manage time and get things done, running two clubs effectively and gettting school work done will be a challenge. I've already been running around like a chicken with my head cut off trying to get clubs up - hopefully more people will step up to the plate soon so more can get done without my direct supervision.

TGA - Started up nicely, lots of new, enthusiastic freshmen - capture the lighthouse went quite well.

BSA - No students, but the new rabbi is interested and one polisci professor is quite into it and has a really neat meditation timer.

Physics Club - Working on organizing talks/lunches. Need to plan events with fire and nitrogen and shotting things out of other things...

Classes - Will computational mechanics be cool or hideously boring? Signs are pointing to boring. Geography of SE Asia may be interesting, but nobody seems to have said anything concrete yet.. Thermo should be new and interesting and research will be something about coherence of photons and storing images on them.

Unless otherwise credited all material by Matt Novenstern