Imaginary Potential

Sorry for the long time since last post. Today I have a shortish lunch talk to all types of physics graduate students. The talk was titled “Physics at Strong Coupling: Why String Theory and Supersymmetry are Ridiculously Cool, Part I,” with future parts to follow in the coming years. The talk went ok, I hope I convinced some graduate students that string theorists are not completely crazy.

But maybe now I can convince you! A friend helped me make the talk a podcast, with audio track and all. You can subscribe to it (and future, podcasts, I guess) here. Hitting “subscribe” on that page imports it into your i-tunes. Let me know if you enjoyed it! I guess, also let me know if you did not enjoy it…

The undergraduates invited Stephen Wolfram last thursday to give the physics colloquium. It was very strange.

For those who don’t know, about five years or so ago Stephen Wolfram, the creator of Mathematica, released a ridiculously large book called “A New Kind of Science.” This book is entirely too large, so I have not read it (see also “The Bell Curve”). So I will have to rely on others who have read, and on his colloquium it to summarize what I understand are some of his points.

The first one is that complex phenomena can be emergent from incredibly simple laws/rules. I don’t think this is a point that anybody really argues with. In fact, I think a lot of current condensed matter theory relies on precisely this fact. In his talk, he spent a lot of time (way too much actually) emphasizing this point. His shtick is cellular automata, some of which can produce ridiculously pseudo-random looking patterns based on very simple rules for how the cells grow. So he spent a lot of time showing very pretty pictures of these automata, which was fine enough.

At some point, the talk took a very weird turn, and he started blatantly advertising the newest version of Mathematica. It really was strange, because the features he was advertising (in real time, on his computer), had seemingly nothing to do with the talk he was giving. Then he said something like: “for the past few years, we have been working on a new piece of software which will accomplish what nobody thought possible. It’s going to be huge and possibly change all of your lives.” He did not elaborate.

After this point, I began to sense frustration from the audience, as it had been forty five minutes, and the man hadn’t actually said anything. All the while, he had been promising to elaborate on his biggest and most suspect claim of the very large book: the simple rules of cellular automata can somehow generate fundamental laws of physics. Finally, with about ten minutes left, he made a series of grandiose claims without elaboration; somehow with cellular automata, the theories of special and general relativity can somehow be derived.

Now, I don’t doubt that Wolfram is a very smart man, smarter than I will ever be. He got his Ph.D. in physics at 20 or something, he invented mathematica. But if you are giving a talk to a physics audience and you have a claim like “GR can be derived from cellular automata,” well, you’d better spent your entire alloted time justifying that claim instead of inappropriately shilling for your software program. Because, if true (which I think I, and most real physicists are very skeptical about), it is ridiculously interesting.

The talk ended with a bit of awkwardness; Wolfram had gone over his time, but was very interested in taking questions from the audience. After a few of them, the undergraduate host tried to get him to stop. Wolfram pleaded for more time, but eventually the undergraduate just cut him off, nobody came out looking well from the exchange.

If, today, you feel as if you should be doing work, but don’t really want to do any, may I suggest a video of a Sidney Coleman Lecture: Quantum Mechanics in Your Face? You’ll learn and be entertained.

The lecture is fantastic and consists of the late, great Coleman discussing a version of Bell’s theorem (which is much easier to understand than the standard treatment), and then going on to discuss the “mysterious” “collapse of the wavefunction”. It’s great stuff. All that’s required for enjoyment is a basic undergrad QM course…

A few weeks ago, I wrote the first script of what I hoped would become a pop-sci podcast. Since this podcast, if it ever happens, will not happen for a rather long time, I figured it’d be fun to make it a series of blog posts. Many apologies if the post seems too simplistic or condescending….

The subject of false vacua is fascinating in its own right, but also nice because it brings together many different areas of theoretical physics. The discussion encapsulates many current areas of beautiful physical research such as quantum field theory, gravity, cosmology, supersymmetry and string theory. There is also a science-fiction like quality about the subject; After all, we’ll be talking about the possibility that at any second a bubble might form out of nothing and eat you. Hopefully, after these podcasts/blogposts the viewer/reader will appreciate that nowadays science fiction is somewhat superfluous; some of the craziest ideas are found in modern physics.

The fusion of Einstein’s special relativity and quantum mechanics under the heading of “Quantum Field Theories,” which describes things that are both very small and very fast. (more…)

Last friday, Mauro (a fellow CTP graduate student) gave the grad student pizza talk about financial derivatives. It was a little bit of a change of pace from the usual (the talks are usually about physics), but was appropriate since Mauro is graduating and currently contemplating what to do for the next phase of his life; financial derivatives are a standard alternative option (as it were) for physics Ph.D.’s.

I’m happy to report that the talk was excellent. The more I learn about financial derivatives, the more interesting I find them. It’s comforting to know that there exist interesting things outside of theoretical physics. It’s more than comforting to know that some of these things can make you money.

Without further adieu, with his permission, here is Mauro’s CTP lunch club talk.

I have no one good thing to blog about, so I’ll blog about a bunch of random things…

Random #1:

Last friday I gave the graduate student lunch talk at the CTP on linear sigma models and extra dimensions in string theory; my goal was to include lots of pictures and make the talk accessible to a wider physics audience than such a talk would normally aim. I don’t think I succeeded (my officemate was refreshingly honest and told me he didn’t understand but liked my pictures). I think it went ok though and got some compliments. I was quite excited to record an audio track to the presentation, make a podcast out of it and post it on the blog. Unfortunately, I spent an hour doing that (it’s quite exhausting to give a talk, even to yourself), only to find out that from 13:01-21:00 for some reason my sound goes out and it sounds like the apocalypse is upon us. Also at various points my hard drive starts spinning RIDICULOUSLY LOUDLY (it’s about to die), and you can hardly hear me. Oh well, guess I’ll have to give it a try again tomorrow.

Random #2:

Here’s a fact. Let’s suppose that one has broken up with one’s long term girlfriend several months ago. Let’s also suppose that she starts seeing someone else and then you decide you’ve made a huge mistake. Let’s further suppose that all one is trying to do is forget about said women. It turns out it DOES NOT HELP to go to what you think will be a relaxing lunch talk only to have her intermediate black hole results cited in the slides! Was it really necessary to cite her t=0.05 s result, sir? Was that integral to your central point? I gave the graduate student speaker (whom I do not know) an earful after the talk. He looked confused. 

Random #3:

Joe Polchinski gave a talk today at MIT whose central theme was the black hole information paradox. If one believes Ads/CFT (which one should, it’s awesome), then it’s really not a “paradox,” because the Hawking radiating black hole can be described as some unitary evolution in a (strongly coupled) gauge theory (living on the boundary of AdS). But this isn’t entirely satisfactory, because one wants a reason why the semiclassical gravity reasoning of Hawking breaks down. His talk reviewed this and talked about some toy models, it was very interesting.

But I was mostly afraid that’d I’d have to meet the guy sometime during the day and that he’d recognize my name. Old time Worldsheet (mostly my grandma, I think) will remember that blogging dave had a little bit of an embarrassment with the famed Dr. Polchinski here (be sure to check the comments!). In the intervening time, actually, I’ve read quite a bit more of Polchinski’s two volume series. At the time of the complaint, I think my mind was just not ready to handle it. But it turns out that given (a lot) of time to ponder over the pages, the book is actually excellent (in a lot of ways it’s like Weinberg’s QFT books). After long sessions with the books, I feel like a Talmudic scholar: exhausted, and like I have seen the face of God. Ok, that’s a bit dramatic….

Open House, Part II

The open house is finally over! Having the newbies here was actually a lot of fun, but a bit exhausting. Towards the end, I think, you straight up run out of things to talk about with them. The week included many free meals and coffees (graduate student staples) and was topped off by a kegger at my place. That’s right, a physicist kegger, and it did not disappoint.

Though, as might be expected, the proportion of men to women was not exactly 1:1, it actually didn’t seem like such an uncool party. Co-blogger Bonna showed up, and, as I remember it, I tried to engage her in a discussion about love, then spilled white wine all over her. 

And then…the cops showed up! They had received “numerous complaints” about the noise! No greater compliment might be heaped upon a physicist party! The po-po and I had a very cordial exchange, where they basically made me close all my windows. Then, seeing the glass bottles on the sidewalk that the recycling truck had failed to pick up that morning, the following exchange went down

Cop: You’d better pick all these bottles up too. People come out drunk from parties, take glass bottles and will smash them against windshields.

Me (a little tipsy, and genuinely puzzled): But you don’t understand, we have a bunch of physicists in there. 

Needless to say, I cleaned up the bottles. 

…were written by Bonna, in her post earlier today. I actually teared up while reading the post about how life happens in grad school. I seem to be doing that a lot lately; I’ve become overly sentimental in my (early!) middle age. Sometimes commercials with cute puppies and babies can get me farklempt. 

 The truth is that Bonna is absolutely right, grad school can be a pretty miserable place (I am in no way mad at you for saying this). You can lay awake in bed, unable to sleep, anxious, wondering if this was really the right decision. You can think about your high school and college friends, who have jobs that seem pleasant enough, that make good money, and leave them with the free time to enjoy it. You can wonder and doubt whether or not that the world of books and papers that contain breathtaking physical ideas and mathematical beauty can really hold a candle to the world of a social life and deep interpersonal connection. And by “you can,” I mean, “I have,” and at length. 

And the truth is, like Bonna, I had no idea that it would be like this at the end of college. Grad school just seemed like a natural extension; I loved and was good at taking physics classes in college, why shouldn’t I continue that? I would even get paid for it! But life kicks in after college in a way that I find difficult to explain (but is probably appreciated by everyone in their mid 20’s and beyond). 

 Chatting with Bonna today, I wondered if, I could meet younger Dave, I would tell him to go to graduate school or not. I told her that I would probably tell him not to. Then I went back to the library and read some incredibly beautiful stuff (see post below) and remembered why I was here, why I loved physics so much, and how, silly as it sounds, my life would be somehow less rich if my brain had never touched such wonderful ideas. So I guess what I would tell younger Dave (YD) depends very much on which day you catch me on (and how research is going at that particular point). 

 The debate I was having with Bonna, and others, about this, is whether or not one should tell open house students “the whole truth,” about grad school, and I think the answer is no. These kids, like YD,  are full of optimism and confidence that physics is what they want to do (”What else would they do?” they think). One shouldn’t (and one couldn’t) dissuade them from going to graduate school in general. When, as a prospective, I heard that “graduate school is a love-hate relationship,” the full implications of that could never be conveyed to me. In fact, that sounded like a more-than-fun concept. Once the students here, I feel like our aim is to convince them that MIT is a pretty damned great place to spend your graduate years, if you’re intent on spending years in graduate school. And that’s a sentiment that I believe 100%, without reservation (though I guess the weather could be nicer). 

Anyway, I’ll blog more about my experiences with the open house once it’s over. The final event is the kegger at my apartment tomorrow night! (And who was just saying life had to be different after college?) 

The supersymmetry club is hitting Seiberg Duality this week! In preparation, I’ve been rereading the very good Argyres notes (here linked is strictly the ‘96 Weyl spinor version; If you want the Majorana version, I might ask you, why do you like unhappiness and pain, sir (or madam)?), and also the book by Terning (which I find less helpful on first reading, but very beautiful once I sort of know the stuff already).

 I also tonight started reading these notes by Strassler, which (though I’ve only read the first fifteen pages or so) are freakin’ incredible!  Why did nobody tell me these notes were so good?! (Answer: Tom and Qudsia have been telling me to read these notes for weeks now). For those who mournfully don’t know about the beauty of Seiberg Duality, there will surely be an explanatory post to follow. I seem to use lots of parentheses in my posts…. 

Ever since our magic “Cosmic Variance” day with 2000 viewers or so, or numbers have been steadily declining; a shame. But I suspected our numbers would be given a slight boost by helen’s most recent racy post.

Indeed, on our “blog stats” page, you can see what the top google searches are that have led people to this blog. Today, no joke, someone googled “Immodesty Blaize Measurements,” and it led him to Imaginary Potential! That’s right, somebody was looking for the semi-pornographic information about the measurements of a burlesque dancer with nipple tassles and was led to our physics blog! Now say we aren’t the coolest physics blog out there.