Memories, Physics, and Celebration

It’s a pleasantly foggy morning here on the USC campus. It is 7:00am now (at least at start of writing), and it will all burn off in a few hours, I imagine, to reveal the sunny sky waiting for us. But right now it reminds me of the Cambridge morning of a couple of weeks ago. A foggy Saturday morning in fact. I took that photo of the spider web I used on Halloween with that mist in the background.

That Saturday of celebration of Andrew’s work (The Andrew Chamblin Memorial Conference) at Cambridge was a remarkable experience. (See here for my first post on Andrew, with tributes.) I was exhausted through a good deal of it, since I had eight hour jetlag, but I’m so glad I went, and that I could contribute a talk. I met many old friends and colleagues, drawn mostly from the UK and European side of Andrew’s collection of friends, collaborators, and admirers in the field.

There were talks by former collaborators of Andrew’s: Gary Gibbons, myself, Roberto Emparan, Robert Caldwell, Raphael Bousso, and Stephen Hawking (who also guided some of Andrew’s thesis work). Gary, in “Discrete Symmetries and Gravity”, talked about Andrew’s early Oxford and Cambridge work on various discrete symmetries in physics, particularly those of a geometrical origin. He’d played with various ideas in this context, including some applications to problems in cosmology and other areas of physics. Gary described some of this work (up to about 1995) in a very interesting talk, pointing out also Andrew’s most recent paper (published posthumously recently with Jeremy Michelson) that uses a few of those ideas.

I spoke about our work together in 1998/1999, in collaboration with Roberto Emparan and Rob Myers. The title was “A is for Action, A is for Andrew”, and the talk was similar to the one I gave at the memorial conference in Louisville. I’ve described a bit of it in an earlier post. I spoke for example about the fun we had collaborating on our first paper together, with Emparan and Myers, on the NUTs and Bolts of AdS. We’d got excited about the fact that the AdS/CFT correspondence had suddenly given meaning to all sorts of computations that people had been perfecting (particulalry the Gibbons-Hawking calculus (as I like to call it) for the thermodynamics of spacetimes) using a whole raft of examples involving gravitational instantons, etc, in a number of contexts. AdS/CFT provided a way of making sense of those objects in a unitary quantum field theory context, and we were excited to work out several examples. Notably, nobody had done the work for Taub-NUT and Taub-Bolt spacetimes, and so that was our first step, and we presented that vey shortly, after a flurry of excited emails while all four authors were scattered around the planet (I was in my New York Summer hideout of that period, for example). We discovered a lovely setup, showing phase transitions from the NUT spacetimes to the Bolt spacetimes very analogous to the Hawking-Page transitions in the context of AdS-Schwarzschild black holes. (I note that Hawking, Hunter and Page later came out with some similar results to ours.)

There are interesting consequences for the dual field theory from this work, some of which are still to be fully understood, since the dual field theory in that case is rather exotic – a certain three dimensional fixed point theory, this time placed on a squashed three-sphere (a type of circle bundle over a two-sphere). (I learned later from Prem Kumar -also at the conference- about some interesting work that he and Sean Hartnoll have done on the field theory side of the correspondence for these examples, just last year, where they were able to confirm a lot of our results in a dual field theory setup using the Klebanov-Polyakov correspondence for O(N) vector models. I need to read that nice-looking paper in detail.)

I then spoke about the physics we worked out governing the phase structure of charged black holes in AdS, giving a phase diagram which I regard as a rough precursor of that of QCD at finite density and temperature. I’ve been thinking about that, trying to get people interested in it, and working further in that area ever since, as a truly promising output of string theory of potential relevance to experiments such as RHIC. I’m happy to say that there’s been a huge resurgence of interest in this very application of AdS/CFT in recent years (see a lovely post on this by Bee and Stephan, with discussion, over at Backreaction), and a lot of aspects of the phase structure of QCD-like models are being worked on and developed quite steadily these days. I think Andrew would have been so pleased to see this sort of “down to earth” application of this type of work taken to this point (and hopefully beyond), given that he spent most of his time thinking about cosmology and black holes, although I should note that he did write (with Fred Cooper and Gouranga Nayak) some nice papers on TeV scale black hole signatures at LHC (See e.g. here and here.). I don’t at all remember how my talk went – I was effectively giving it at 3:00am (according to my body clock). A good sign is that I finished on time. When I am truly out of sorts due to jetlag, my perception of time goes awry, and I can look at the time, see that it is over, and that i’ve only got about 2/3 of the way through the talk. I did this for a job talk once. One of the perils of selling your wares on an international market.

Roberto Emparan was up next, talking (with title “Einstein in Mordor: Black Rings in Higher-Dimensional Gravity”) about higher dimensional black hole and black ring solutions. Andrew had made some early observations in this area in unpublished work and conversations with Roberto and Harvey Reall, and he went from talking about that to giving an update of the state of that area. It is actually quite a fascinating topic, with several curious results that I have a feeling are answers waiting for a question (besides the interesting one of classification).

We then broke for lunch and went wandering around Cambridge looking for somewhere nice to eat. This was a good chance to chat with some of my friends and colleagues who are not based in the UK, and generally hear some things about the field in general, and various research ideas in particular.

Up next was Robert Caldwell, with a talk entitled “Some Observational Consequences of Dynamical Dark Energy”. I missed the beginning, so cannot let you know if there was a direct connection to work in collaboraton with Andrew, but it was a very interesting talk. He was followed by Raphael Bousso, (“Predictions in the String Landscape”) who told us about some of his new ideas in the area of inflationary cosmology, focusing on what’s often called eternal inflation, and issues of predictability within such scenarios. I think that there’s a preprint out recently with similar content to that of the talk.

Stephen Hawking, after some nice remarks about Andrew and his work (including their ground-breaking paper together with Harvel Reall on black holes in the context of brane worlds), told us (“The Universe on the Brane”) about some ideas in brane-world cosmology in an AdS/CFT-like setting. I confess that I did not understand it very much, and so cannot tell you anything coherent. I imagine that there will be a paper about it, if the idea comes to fruition.

After the day of talks, we met again shortly after for the pre-banquet drinks and the banquet itself. This was held near the old kitchens in the heart of Trinity College itself (the talks were at Trinity too, but in newer facilities outside the main grounds). This gave everyone a chance to mill around and chat about all sorts of things, including sharing stories about Andrew, reminiscing about the old days, etc. There were plenty of new physics thoughts had as well. Recalling some of the seven and eight year old work I did with Andrew was fruitful, spurred by two main reasons. The first is that people asked me questions about it. These were often questions I once knew the answer to, and this forced me to either re-construct the answers, or work them out again, sometimes arriving at a new way of thinking about something. This usually led to new ideas for projects. The second reason is that a lot has happened in the field since those papers were written, and I certainly don’t keep up with everything that has happened. So people told me about things that got me thinking about new ideas. In some cases, I remembered that I’d intended to do a project on one area or another, and simply never got around to it. I suspect that there were similar conversations had by lots of other people, so the scientific value of such memorial conferences can be extremely high, especially since it can bring together people from so many different approaches and topics, as was the case here.

The banquet was excellent, of course. Trinity’s kitchens were in good form, as were the serving staff, who were a pleasure to watch. They have some nice touches to their performance that are worth looking out for. As an example, when serving a course, they burst forth from the side doors all smartly turned out, and walk crisply to various points all around the tables (which were gathered into a single table in the shape of the head a three-tined fork, or a giant “M” or “W” if you prefer). Only when they are all in position does one of them give a nod, and then they start serving. So everyone gets their course, and begins eating, at the same time. Nice professional touch that you usually only see at banquets at the finer restaurants. Here’s a portion of the table:

There were speeches afterward, over port. Harvey Reall led off, and gave a very touching series of remarks, reminiscences, and anecdotes.

He then opened the floor to others to stand up and say some remarks, tell stories, etc. Someone whispered in my ear that I should talk about the hike I recalled from near Aspen (mentioned in an earlier post). I must admit that here I was really lost. At Louisville, I was able to stand up at the memorial service and speak at length about Andrew, his work, his friendship, his influence, and how much I’d miss him. I could not do this at Cambridge. I think that the reason was two-fold. The lesser part of it was my jetlag. The greater part was that I could not shake the feeling that at any minute Andrew would walk in through the door with a big smile on his face. Being in Cambridge, at table in college, is one of the things Andrew loved so much, and where I saw him at his most happy, and at ease. So that whole day it just seemed utterly unreal that he was not really coming back. I could not make a speech of any sort under those conditions. I said a few words, mumbled that I missed him, and sat back down after maybe a minute. I hope I did not confuse or disappoint anyone, especially Andrew’s brother Jonathan, who was there representing the family. I just could not do it, and I still feel awful about it today.

In scenes reminiscent of Andrew’s favourite practice, many groups of us sat at table in relaxed fashion long after many had left, sitting around talking about everything under the sun (and beyond) until the wee hours of the morning. And then afterwards a few of us (Raphael Bousso, Neil Lambert, (both fellow students with Andrew in Cambridge), John Whelan, and myself) stood in the street at the entrance to Trinity and talked even more, for at least another hour. This was the most sad part of the evening for me. Neil was one of the organisers of the day’s events and I think that with us standing outside Trinity, with the event over, he was able to focus on really missing Andrew for the first time that evening. He was so upset over missing his buddy -they’d known each other since their student days at Cambridge and remained close all the way through- and it showed.

Well, I think I’ll stop here, ending on what I hope is a lighter note with a strange occurrence. I still don’t fully understand the backstory here. Toward the end of the four of us standing in front of Trinity talking about the field now, the field back in the good old days of the Revolution in 1995, and about working with and spending time with Andrew. We were pondering the wisdom of yelling in unison (a suggestion from Neil) “God damn it mother f**king piece of shit!” at the top of our voices, as a sort of venting to cap off the day, and get past the loss of our friend. It would have meant something to us, of course, and the porters just inside the gate and anyone walking by would just have thought we were another bunch of drunken yobs, tourists or students, who should be home in their beds.

Well, we did not get to the point of the aforementioned yelling. Two genuine yobs came along and introduced themselves drunkenly, asking us if we could get them into Trinity’s grounds (the locked gates at this time of night luckily prevent this from happening unsupervised). Of course, we said no, and hoped they would wander off. One of them, English I think, said that he was in the military (not sure why that’s relevant) and that his companion was visiting him (from the USA, I think) and that he wanted to show him the inside of Trinity. We again politely declined to help, claiming -correctly- that it was not in our power to do so.

Anyway, they were turning to leave when one of them asked us who were were and what we do. Were we students at Cambridge? So we said we were not students, but faculty from various places. What field? Physics, we said, a lot of us work on something called string theory. The English guy immediately said, gesturing in a dismissive way, “String Theory?! Oh… That’s so 1995!”. They walked away. We looked at each other in a state of incredulity for a moment, saw the irony and humour in the whole thing, and soon went our separate ways to sleep off the long day.

-cvj