Category Archives: string theory

Festival of Joe

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20140226-214941.jpgEarly evening. Cocktail (made with Hendricks gin, muddled tangerine, and basil…). Roast pork on the way. Old haunt.

Where am I? At Roy’s, in Santa Barbara. I’m here for a two day celebration of the work of Joe Polchinski, one of the giants of my field. It all begins tomorrow, and I am taking the opportunity to have a quiet bit of time in an old haunt. I was a postdoc of Joe’s back in the mid 1990s, just when the world of theoretical physics was waking up to the awesome power of D-branes. D-branes are a special type of dynamical extended object in physics, and Joe had discovered their importance for string theory just around that time. Roy’s opened around that time too, if I recall, and a group of us became regulars, helping it along in those early days when it was smaller than it is now. (That small group included my friend and fellow postdoc Andrew Chamblin, who passed away some years ago.)

A D-braneSo I am here to help celebrate Joe’s work on the occasion of his 60th (hard to believe that number, frankly), and it will be good to see all the people who show up, and of course it’ll be excellent to see Joe. Part of my help in the celebrations is to organize and run a panel about D-branes, which will be on at 11:00 tomorrow. I’ll be reflecting a bit on the good old days when D-branes really broke, and turned out to be the key tool of the Revolution that took place in the field. In lectures and writings from that time and long after I used to refer to them as the Heroes of the Revolution, and in honor of that and of Joe I have named this session D-Branes, Tools of the Revolutionary, or something like that. Joe helped bring about the revolution, and his tools were D-branes, you see.

I was lucky to be here as a postdoc at that time, and happily I had the good sense to be quite sure that it was going to be important to quickly spread the […] Click to continue reading this post →

Summing Numbers in a Small World

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So here’s a slightly weird thing. So there’s been all this excitement over the web about the old old “shocker” that the sum of the positive integers is -1/12. You know, not even an integer, and not even positive. Apparently there have been articles in the New York Times and Slate and goodness knows where else… and I’ve been ignoring it all since I’m tired of what it often leads to: People wilfully using it as a device to manipulate people’s ignorance about subtleties with infinite processes to make the tired point that string theory is somehow wrong since it is based on “funny math”. I called Lawrence Krauss (who should have known better) out about it some years ago when he did that at an event I happened to attend. It’s a bit tedious, not the least because it is actually part of a wonderful field of mathematics that can get misrepresented, and of course because it has nothing to do with string theory.

So I ignored it all. Then some students in my class asked me about it. And I explained why it is interesting and so forth… Then I carried on ignoring it all.

Then a day or two ago a mathematician colleague emailed me to ask what […] Click to continue reading this post →

Hawking an Old Idea

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On the one hand it is good to get members of the general public excited about scientific research, and so having some new excitement about something Stephen Hawking said, driven by gushingly written articles in the press and online, can be good. On the other hand, it is annoying that the thrust of the articles are largely that he’s stunned the world again with a brilliant and unlooked-for idea. People just lap this stuff up, unquestioningly. It is actually an old idea (and in fact one that is being mis-reported – see below). One’s instinct is to just say “Welcome, Stephen, we’ve been waiting for you to join us”, or “Come on in, the water’s lovely”, and just move on, but it seems so unfair. The thing that’s most puzzling in all of this is Hawking’s own paper (which is all of two pages of words – a transcript of a talk he gave in August), which makes no reference at all to (for example) Samir Mathur’s work, which has been explicitly saying essentially the same thing for well over a decade, with a very definite proposal for how it might work. That work has hardly been buried in obscurity. Samir and many other people who have liked his idea have been working out the consequences of the proposal in numerous papers for over a decade and reporting on their results at all the main conferences, and even talking to him about it (I note that Samir was in the audience during the August talk and even politely asked the speaker to compare and contrast the similar-sounding proposals). So it is puzzling that you get no hint from the paper’s citations that this is a well-considered and ongoing idea, even if (perhaps) in detail it may pan out differently from other suggestions.

light cones in spacetime with a compact mass - a black holeWhat’s the idea?, you ask. Well, it is not, as you might get from most of the articles (somewhat confusingly), that black holes do not exist. It is that the black hole’s event horizon, thought of as a sharp “point of no return” boundary, may not exist. Instead, it is approximation or shorthand for the complicated physics (of both matter and spacetime) that happens in the vicinity of the black hole. Simply put, the horizon arises in classical solutions to classical (i.e. non-quantum) equations (such as in General Relativity) of gravity. (See an earlier post I did about them here, from which came the illustration […] Click to continue reading this post →

Ten Things…

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black_hole_phil_club_talkSo I’ve been a bit quiet as I’ve had a lot going on. This includes preparing ten interesting slides to use as props for a talk I gave this evening to the USC Philosophy Club. It was entitled “Ten Things YOU Should Know About Black Holes”. It started with the original idea by Michell in 1783 (yes, really, that early!) and ended with topics of current research (what is the fate of the singularity? What really happens at a horizon? Etc., etc…) I spoke for a while and then fielded tons of questions, and am now (I am writing a draft of this on the subway train home – uploading later) suffering from a rather broken voice due to too much talking and projection…. Gosh. But it was fun. A really […] Click to continue reading this post →

Weinberg on Physics Now

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I just spotted (a bit late) that Steven Weinberg (one of the giants of my field) has written a piece in the New York Review ofBooks entitled “Physics: What We Do and Don’t Know”. I recommend it. He talks about astronomy, cosmology, particle physics, and by casting his eye over the arc of their recent (intertwined) histories of ideas, experiments and discoveries, tries to put the Standard Models of particle physics and of cosmology into perspective.

The article is […] Click to continue reading this post →

SCSS San Diego

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dinner_pic_cvjFriday’s meeting was rather nice. There was a really good turnout (especially from UCLA) and so in the end we had the perfect combination of an attentive and receptive audience and four really good speakers. As per design of the whole thing, plenty of time was allowed for discussion and pedagogy, and so I got the feeling that people felt really comfortable raising points during the talks and also chatting further during the breaks and lunch and dinner. It was really good to catch up with friends and colleagues from groups in the area, […] Click to continue reading this post →

Different Teacup, Same Storm

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Meanwhile, poor Matt Strassler, who means well, is re-discovering the frustratingly convenient (for some) fact that blogs (or is it blog readers?) have no memory for stuff that has scrolled off the page, so attention-seekers get to make the same deliberately wrong claims and misrepresentations they did before, and that were thoroughly addressed before, and a whole new bunch of people who want to learn a bit of science will be drawn in to a non-debate, not knowing that none of this is new. Attention-seekers get the attention they desire, and since attention is the main point for them (not actual progress in science, oh no, not at all!), they succeed.

Matt is discovering this now… By trying to discuss a little nuance about what recent discoveries at the LHC may or may not mean for string theory, he has wandered into the same old tired shouting match about string theory with attention seekers who have nothing better to do but put their hands over their ears and yell misleading slogans from the sidelines to generate fake controversy, and/or split the world into pro-string vs anti-string which is so simplistic and, frankly, juvenile. An interesting game, if you’re up for it, would be to look at the noise in the long comment stream there, and then look at almost any of my Scenes from a Storm in a Teacup posts (from 2006!!!) and the long comment streams accompanying them (look at, for example IV, V, and VI), and see if you can see the same sorts of patterns. I deliberately collected those posts together to form a partial* record of some of that time’s discussion for precisely this purpose, for those who care to read and see that all attention-seekers (who have no real interest in letting science research run its course) have to do is wait for a while and then start yelling the same faux claims all over again to get attention, sell books, enlarge their mutual admiration society membership, etc.

You know, all this behaviour is hardly different from that of the annoying squirrels I have to deal with at my fruit trees from time to time. Not being so good at cultivating [..] Click to continue reading this post →

Phase Diagram

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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 →

News from the Front, X: Smoother Transition

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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 →

SCSS Report

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scss_may_2013Friday’s Southern California Strings Seminar was a success! Thanks to all who came, who spoke, and the UCLA organizers. I enjoyed all four talks that were put on, and learned a lot from each. (Sera Cremonini is giving her nice talk about duals of hyperscaling violating theories in the photo.)

I was particularly pleased about the talk by Daniel Harlow about the Firewall issue, […] Click to continue reading this post →

Southern California Strings Seminar

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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?

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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

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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

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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 →