Phase Diagram

phase_diagramFor those who have a thirst for something physics-y to follow the tomato chutney post, here’s a decorated physics diagram I made in Matlab this morning. Click for a larger view. It’s the phase diagram of interesting black hole transitions* (that I co-discovered 14 years ago) associated with part of the story I mentioned last month. On the right of the line you have small black holes favoured (of a given charge, so move horizontally), and on the left side of the line the system favours large black holes and so when you cross the line you have a sudden jump from one type to the other. That second order critical point I talked about there is the end of the line of first order points. The blue dot. Above there, you cross over smoothly from small to large holes. The blue dot is the border between the two cases.

It is a bit like having steam (or water vapour) on the left and liquid water on the right, and crossing the line is what you call boiling. The second order point is the place […] Click to continue reading this post

Steamin’

CPU_usageYeah! It feels great when I get the workhorse computer really chugging along. 85% is unusual to see on a normal run, since this beast (a 2010 3.32 Ghz Mac pro quad core) has a lot of computational capacity that you don’t need for most tasks. I’m getting up to 85% because all four cores are crunching away independently on the same problem (written in MatLab) but different parts of it. Each point on the resulting graph will be the result of having computed 2000 points. Each of those 2000 points comes from computing a boundary value problem discretized into a million points. See an earlier post for more about that.

(Update: Now running even more tasks associated with this problem: Up to 96% now:
CPU_usage_2
…with nothing idle at all. This is probably not as efficient any more, but it is for a few hours and then back to 85%. In the meantime, it is amusing how it makes me feel I’m doing more work somehow…)

I assigned different parts of the graph to different processes by hand, not using a […] Click to continue reading this post

News from the Front, X: Smoother Transition

second_order_transition_1Yesterday I submitted a new paper to the arxiv. This is is my favourite curve from it. Some of you who follow the blog will recognize the blue circle-dots and guess that this is the output of the dot-generation I’ve been tinkering away at (and reporting on somewhat cryptically) since April (see e.g. here, here, and here). Correct. There are many reasons why that is the case. One of them might well be because it looks like a very comfy chair, and by time I’d submitted the paper, I was rather tired. I’d pulled an all-nighter to finish the paper because I wanted to submit it by noon yesterday, and the night before I had to spend several hours at a social event.

So once it was an appropriate time to leave the place I was at, I said my goodbyes, jumped on my bike, pedalled home, all_nighter_things put on some coffee, some Ana Tijoux (through headphones, so as not to wake anyone. Why her? Kinetic energy was what I needed at that moment – her vocal style is full of that. Try “La Bala” or “1977”. It is in Spanish, but that’s just fine.), and from 10:30pm to about 12 hours later, ground out the paper. I had to do this since I took some time away from the research project for a week, and then on Tuesday evening noticed the title and abstract of a new paper on the arxiv that suggested some overlap with what I was doing. So I had no choice but to gather all the results I’d been gathering the last several weeks and write them up and get them out, putting off reading the other paper until afterwards, so as to remain independent. Hence the all-nighter to finish it all. It was a pretty easy paper to write since I’ve had the results for a while, knew what I wanted to say, and it was just a matter of pulling everything together and writing a lot of background to set the scene for the results. A fair amount of the time was spent fiddling with things like how to generate figures from Matlab that embed nicely into the text, and so forth. Technical tedium.

The physics? Another reason I like the above curve is because it examines physics from an old favourite phase transition I co-discovered almost 14 – gosh yes, cvj, fourteen! – years ago. To my knowledge it is perhaps the earliest example of a […] Click to continue reading this post

Effective

I just learned* that Ken Wilson died a few days ago (Just 15th). Wilson is another of the giants that you don’t hear much about in the popular media coverage of the great ideas in Physics that form the bedrock of so much of what we do. You still get people saying utter nonsense about “hiding infinities” in physics and so forth (often in discussions on blogs and various similar forums (fora?)) because what he taught us all about effective field theory and the renormalization group still is only taught in some advanced classes on quantum field theory (and still not as well or frequently as it should be in such classes … it has only relatively recently begun to be put at the forefront in textbooks on the subject, such as Tony Zee’s). In the cut and thrust of the mainstream of research though, I’m happy to see that so much of Wilson’s legacy is in the most basic fabric of the language we use to discuss results and ideas in particle physics, condensed matter physics, quantum gravity, string theory, and so forth.

I had the distinct privilege of having Joe Polchinski as a mentor for some of my postdoc years, who is known as being one of the current giants on the scene who […] Click to continue reading this post

Southern California Strings Seminar

The group at UCLA is hosting the next SCSS, and it is on Friday. More details here. The schedule looks good:

9:30-11:00 Sera Cremonini (Texas A&M): “Probing the IR of hyperscaling violating geometries.”

11:15-12:45 Ken Intriligator (UCSD): “Aspects of 3d N=2 Chern-Simons-Matter Theories.”

12:45-2:15: Lunch

2:15-3:45: Daniel Harlow (Princeton): “On the Computational Complexity of Hawking Radiation”

4:00- 5:30: Eric D’Hoker (UCLA): “Supermoduli and supersymmery breaking”

Enjoy!

-cvj Click to continue reading this post

Something’s not quite right, perhaps?

thing_vs_thing Yeah. Scary, right? I woke up one morning to this result (see earlier posts here, here, and here) from a night of an intensive computer run. It was not meant to be a straight line, but pretty close to it, so I knew that something was wrong with my code. Took me a good long while to trace the problem, but I did in the end. My signal was being swamped by both […] Click to continue reading this post

Lines of Thought

So I’ve moved on to curved lines now, in case you’re wondering. 🙂 (See previous posts.) The last several days (the research parts) have been taken up with more computations. A lot of the time has been spent calibrating the programs, and trying to assess and understand and characterize the inevitable errors that show up, by running the programs and checking the resulting plots of data points against expectations shaped by hand calculations. Calculating on the train to and from work, I’ve filled several pages of my small notebook with computations, alongside sketches of some of my surroundings as usual (people mostly). As a result (fingers crossed) I think I’ve now understood all the key aspects of the results I’ve been getting, and have good numerical control of things. To get such control, I’ve had to push the error tolerance and the size of the grid of points I’m computing on to regimes where I’m back again to waiting for the better part of an hour for each data point. (One sets up the problem on the computer by making continuous variables, such as space and time, into discrete ones, forming a grid. The problem is then to use various […] Click to continue reading this post

A Much Shorter Straight Line

LinePlot2 How is the line coming along? It is very kind of you to ask (if indeed you were). Well, there it is to the left. (See the previous post for background.) In the end, I abandoned Maple since it was taking way too long to do each point, and just for the simple example. (When I tried to do one sample point of the complicated example it took 24 hours and I stopped it before it was done!) The point is that Maple does not easily […] Click to continue reading this post

A Very Long Straight Line

I’ve been multitasking in an interesting way. Sort of. I’ve reached a certain point with some computations I am doing that I cannot go beyond by analytic means. LinePlotThis means that I can’t extract the physics I need by doing algebra and other exact manipulations on paper any more. Progress can continue however by using numerical means, employing a computer to solve the highly non-linear equations and extract the juice. There are several steps involved, and ultimately, I want to determine how a certain physical quantity depends on another physical quantity. (I’m sparing you the trouble of knowing what the details of the physical quantities are, since it does not matter for the thing I am trying to tell you. It relates to quantum field theory, gravity, and string theory, which connects the two.)

I can see that dependence quite clearly if I simply plot a graph of one versus the other, and in this case I need the computer to work out what the points on that graph are. I actually don’t know the answer for the cases I really am interested in, nobody does (that’s why it is research!), and so that’s what I want to find. I want lots of points to get a nice smooth graph, so the computer has to compute a lot of points, and I need to run it for a long time since I want it to compute the points very accurately. So I wrote a program (in Maple) to work on the problem, studying just one […] Click to continue reading this post

TED Youth Talk – Hidden Structures of the Universe

cvj_TED_YouthYou might recall that last year I gave a talk at TED Youth, in their second year of short TED talks aimed at younger audiences. You’ll recall (see e.g. here and here) I made a special set of slides for it, composed from hundreds of my drawings to make it all in graphic novel style, and somehow trying to do (in 7 minutes!!) what the TED people wanted.

They wanted an explanation of string theory, but when I learned that telescopesI was the only person in the event talking about physics, I kind of insisted that (in a year when we’d discovered the Higgs boson especially!) I talk more broadly about the broader quest to understand what the world is made of, leaving a brief mention of string magnifytheory at the end as one of the possible next steps being worked on. Well, they’ve now edited it all together and made it into one of the lessons on the TED Ed site, and so you can look at it. Show it to friends, young and old, and remember that it is ok if you don’t get everything that is said… it is meant to invite you to find out more on your own. Also, as you see fit, use the pause button, scroll back, etc… to get the most out of the narrative.

I’m reasonably pleased with the outcome, except for one thing. WHY am I rocking […] Click to continue reading this post

Congratulations!

In other interesting announcements today, the great physicist Alexander Polyakov has been given the Fundamental Physics Prize. (See the announcement here.) There was a remarkable award ceremony in Geneva yesterday, hosted by Morgan Freeman, and with lots of Physicists and others celebrating great work in various areas of physics. Polyakov has been a key and brilliant leader in many areas of theoretical physics, and influenced so many ideas and techniques that have fed into the whole field, and so this is a well deserved recognition.

I must note that it is a bit sad (to say the least) to do a google search on the news about this prize and see so many articles with a lot of just plain stupid focussing on a big prize going to a “string theorist”, as though this is somehow negative or ironic, and also missing the fact that Polyakov’s contributions are so broad and far-reaching […] Click to continue reading this post

Known Unknowns Decreased a Bit

Well, the day is here. The Planck collaboration has announced a huge amount of results for the consumption of the scientific community and the media today. The Planck satellite looks with unprecedented precision at the very earliest radiation (“cosmic microwave background radiation”, CMB) from the universe when it was very young (a wee, cute 380,000 years old) and helps us deduce many things about what the universe was like then, and what it is like now. Here’s one of the representations of the universe using the new sky mapping Planck did (image courtesy ESA/Planck):

There’s a ton of data, and a raft of papers with analysis and conclusions. And there’s a very nice press release. I recommend looking at it. It is here, and the papers are here. The title of the press release is “Planck reveals an almost perfect Universe”, and some of the excitement is in the “almost” part. A number of anomalies that were hinted at by the previous explorer of the CMB, WMAP, seem to have been confirmed by Planck, and so there are some important things to be understood in order to figure out the origin of the anomalies (if they ultimately turn out to be real physics and not data artefacts). [Update: Andrew Jaffe has two nice posts I recommend. One on the science, and the other on the PR. Jester also has a nice post on the science from a particle physicist’s perspective.]

What is the title of my post referring to? Well, the refined measurements have allowed us to update some of the vital statistics of the universe. First, it is a bit older than previous measurements have indicated. The age is now measured as 13.82 billion years. (I’m already updating pages in the draft of my book…) Second, the proportion of ingredients […] Click to continue reading this post

We have a Higgs!

So it’s very much worth noting that there are some new announcements from earlier this week concerning last years’ landmark discovery at the Large Hadron Collider. The news is that a Higgs particle was discovered. There were several news stories about it in the last few days. This might be a bit confusing, and many of you are thinking that this is recycling news from last year concerning the discovery of the Higgs. It is not recycling. If you go back and look at the results that were announced last year, there was an important note of caution, notable in the fact that the particle discovered was referred to as “Higgs-like”. More analysis was needed to be sure that it was indeed a particle that fits the name Higgs. Well, that analysis has been done, with more data included and so forth, and both experiments (CMS and ATLAS) are now sure that they are seeing a Higgs particle, and indeed it is one that is very close to what you’d expect for the Standard Model of particle physics.

The latter is is important and interesting to note, since many people expect that there […] Click to continue reading this post

Local Connections

Well, Thursday’s meeting was a blast! I had decided not to try to get people to RSVP for the meeting this time, and so when it came down to the day before, I had no idea how many were going to show up. This meant that I had to make some guesses about how much coffee and tea and cookies to organize, which was a little bit of a challenge. But just before 9:00am people began to show up, and kept showing up, and by time I was ready to start off the day’s meeting, there was a really good crowd!

In the end it was a great day, with five really good talks and lots of excellent discussion. […] Click to continue reading this post