Ok, I promised to explain the staircase I put up on Monday. I noticed something rather nice recently, and reported it (actually, two things) in a recent paper, here. It concerns those things I called “Holographic Heat Engines” which I introduced in a paper two years ago, and which I described in some detail in a previous post. You can go to that post in order to learn the details – there’s no point repeating it all again – but in short the context is an extension of gravitational thermodynamics where the cosmological constant is dynamical, therefore supplying a meaning to the pressure and the volume variables (p,V) that are normally missing in black hole thermodynamics… Once you have those, it seems obvious that you can start considering processes that do mechanical work (from the pdV term in the first law) and within a short while the idea of heat engines in which the black hole is the working substance comes along. Positive pressure corresponds to negative cosmological constant and so the term “holographic heat engines” is explained. (At least to those who know about holographic dualities.)
So you have a (p,V) plane, some heat flows, and an equation of state determined by the species of (asymptotically AdS) black hole you are working with. It’s like discovering a whole new family of fluids for which I know the equation of state (often exactly) and now I get to work out the properties of the heat engines I can define with them. That’s what this is.
Now, I suspect that this whole business is an answer waiting for a question. I can’t tell you what the question is. One place to look might be in the space of field theories that have such black holes as their holographic dual, but I’m the first to admit that […] Click to continue reading this post
This just in. Marvel has posted a video of a chat I did with Agent Carter’s Reggie Austin (Dr. Jason Wilkes) about some of the science I dreamed up to underpin some of the things in the show. In particular, we talk about his intangibility and how it connects to other properties of the Zero Matter that we’d already established in earlier episodes. You can see it embedded below […] Click to continue reading this post
My friends over at UCLA took the reins for the regional meeting known as the Southern California Strings Seminar this semester, and the shot above (a tad blurry) is from the event, which was today. We had four excellent talks (I […] Click to continue reading this post
(Click for larger view.) The answer’s still no, but I still amuse myself with the joke. (Alternative forms would have been “The New Expendables Poster?” or “Sneak peek at the Post-Infinity Wars Avengers Lineup?”…) This is a photo that I was thinking would not make it out to the wider world, but that’s probably because I was not paying attention. We spent a lot of time on that rooftop getting that right – no it was not photoshopped, the city is right behind us there – as part of the “Frontline Scholars” campaign for USC’s Dornsife College of Letters Arts and Sciences… and then the next thing I heard from our Dean (pictured three from the right) is that he is now our ex-Dean. So I figured the campaign they were planning would not feature him anymore, and hence this picture would not be used. But I think the photo was actually in use for the campaign for a while and I did not know since I don’t actually pay attention to […] Click to continue reading this post
Turns out that it still a lot of fun to lecture about string theory and D-branes! (The latter are an important type of extended object, generalizing membranes, that have been very useful in theoretical physics for the last 20 years. — My goodness, it has been 20 years since Joe Polchinski first demonstrated their importance for string duality!) The students at the Latin American String School here in Mexico City seem to be very engaged and enjoying themselves. Although I was having fun I was also not without a presentation error or two brought on by […] Click to continue reading this post
Snapshot of my doodles done while talking on the phone to a BBC producer about perhaps appearing in a film discussing anti-gravity*. I explained lots of things, including why General Relativity does not seem to like negative mass, partly because they have something called a “naked singularity”, which is a big problem. Only after the call ended did I recall that in 1999 I co-authored a paper in which we discovered […] Click to continue reading this post
Here, as promised yesterday, is the fun conversation at Screen Junkies. I don’t need to say much, since much of what I wanted to talk about (extra dimensions, other laws of physics, parallel universes, etc) made it to the (awesomely cut, btw!) episode! Embed of video below.
Enjoy! […] Click to continue reading this post
So Tuesday night, I decided that it was imperative that I paid a visit to one really good restaurant (at least) before leaving Santiago. My duties at ICMP2015 were over, and I was tired, so did not want to go too far, but I’d heard there were good ones in the area, so I asked the main organizer and he made a recommendation.
It was an excellent choice. One odd thing: the hotel is in two separate towers, and I’d noticed this upon arrival and started calling it The Two Towers in my mind for the time was there. Obviously, right? Well, anyway, the restaurant is right around the corner from it plus a two minute walk, and…. Wait for it…it is called Le Due Tonni, which translates into The Two Towers, but apparently it has nothing to do with my observation about the hotel, since it got that name from a sister restaurant in a different part of town, I am told. So… An odd coincidence.
I will spare you the details of what I had for dinner save to say that if you get the fettuccini con salmon you’re on to a sure thing, and to warn that you don’t end up accidentally ordering a whole bottle of wine instead of a glass of it because you’re perhaps used to over-inflated wine prices in LA restaurants (caught it before it was opened and so saved myself having to polish off a whole bottle on my own)… Another amusing note is that one of my problems with getting my rusty Spanish out for use only occasionally is that I get logjams in my head because vocabulary from Spanish, French, and Italian all come to me mid sentence and I freeze sometimes. I’d just been getting past doing that by Tuesday, but then got very confused in the restaurant at one point until I realized my waiter was, oddly, speaking to me in Italian at times. I still am not sure why.
It was a good conference to come to, I think, because I connected […] Click to continue reading this post
One of the towering giants of the field, Yoichiro Nambu, passed away a short while ago, at age 94. He made a remarkably wide range of major (foundational) contributions to various fields, from condensed matter through particle physics, to string theory. His 2008 Nobel Prize was for work that was a gateway for other Nobel Prize-winning work, for example 2012’s Higgs particle work. He was an inspiration to us all. Here’s an excellent 1995 Scientific American piece (updated a bit in 2008) about him, which nicely characterises some of his style and contributions, with comments from several notable physicists. Here is a University of Chicago obituary, a Physics World one, one by Hirosi Ooguri, and one from the New York Times. There are several others worth reading too.
Since everyone is talking more about his wonderful work on symmetry-breaking (and rightly so), I’ve put up (on the board above) instead the Nambu-Goto action governing the motion of a relativistic string (written with a slight abuse of notation). This action, and its generalisations, is a cornerstone of string theory, and you’ll find it in pretty much every text on the subject. Enjoy.
Thank you, Professor Nambu.
-cvj Click to continue reading this post
Here’s some interesting Sunday reading: Frank Close wrote a very nice article for Prospect Magazine on the business of testing scientific theories in Physics. Ideas about multiverses and also string theory are the main subjects under consideration. I recommend it. My own thoughts on the matter? Well, I think most … Click to continue reading this post
There’s an SCSS today, at USC! (Should have mentioned it earlier, but I’ve been snowed under… I hope that the appropriate research groups have been contacted and so forth.) The schedule can be found here along with maps.
-cvj Click to continue reading this post
I just learned of an excellent interview with Edward Witten, one or our field’s grandmasters, or rather: the grandmasters’ grandmaster. I strongly recommend reading it. (This is for technically equipped people working in the field, most likely – I believe that it is not intended for the general public, although you are welcome to read it too!)
There’s a lot of discussion (of among other things like his current work) of that golden period during the 1990s that I had the privilege to work in during my postdoc years (some of them under the guidance of Witten) that remain one of […] Click to continue reading this post
Yesterday I sneaked on to campus for a few hours. I’m on family leave (as I mentioned earlier) and so I’ve not been going to campus unless I more or less have to. Yesterday was one of those days that I decided was a visit day and so visit I did. I went to say hi to a visitor to the Mathematics Department, Sylvester James Gates Jr., an old friend who I’ve known for many years. He was giving the CAMS (Center for Applied Mathematical Sciences) distinguished lecture with the title “How Attempting To Answer A Physics Question Led Me to Graph Theory, Error-Correcting Codes, Coxeter Algebras, and Algebraic Geometry”. You can see him in action in the picture above.
I was able to visit with Jim for a while (lunch with him and CAMS director Susan Friedlander), and then hear the talk, which was very interesting. I wish he’d had time to say more on all the connections he mentioned in the title, but what he did explain sounded rather interesting. It is all about the long unsolved problem of finding certain kinds of (unconstrained, off-shell) representations of extended supersymmetry. (Supersymmetry is, you may know, a symmetry that […] Click to continue reading this post
Since people were asking for copies of my slides from my colloquium chalkboard-style talk on black holes and the things I call “holographic heat engines” last month at Harvey Mudd College, I decided to export them as a movie. You can find it on YouTube. Link below. It was a 50 minute talk, but all the builds are compressed down to a 6 minute file! I try to keep the bulk of the narrative in my head and speak it with the slides as visual aids (instead of writing everything on the slides as is often the practice) and so I do not know […] Click to continue reading this post
Hello from the Aspen Center for Physics. One of the things I wanted to point out to you last month was the 74 questions that Andy Strominger put on the slides of his talk in the last session of the Strings 2014 conference (which, you may recall from earlier posts, I attended). This was one of the “Vision Talks” that ended the sessions, where a number of speakers gave some overview thoughts about work in the field at large.
Andy focused mostly on progress in quantum gravity matters in string theory, and was quite upbeat. He declines (wisely) to make predictions about where the field might be going, instead pointing out (not for the first time) that if you look at the things we’ve made progress on in the last N years, most (if not all) of those things would not have been on anyone’s list of predictions N years ago. (He gave a specific value for N, I just can’t recall what it is, but it does not matter.)
He sent an email to everyone who was either speaking, organising, moderating a session or similarly involved in the conference, asking them to send, off the […] Click to continue reading this post