Worth a read: This is ‘t Hooft’s summary (link is a pdf) of a very interesting idea/suggestion about scale invariance and its possible role in finding an answer to a number of puzzles in physics. (It is quite short, but think I’ll need to read it several times and mull over it a lot.) It won the top Gravity Research foundation essay prize this year, and there were several other interesting essays in the final list too. See here.
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.
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
…Or at least, not always the fire you’re looking for. So, as suspected for several months now, the signal seen by BICEP2 experiment and dubbed “a smoking gun” type of direct evidence for cosmic inflation (for which we have lots of strongly suggestive indirect evidence, by the way) is likely an artefact of the effects of galactic dust. I spoke about this in a post a while back, so I won’t repeat myself here. What everyone has been waiting for has been the results of a joint analysis between the BICEP2 people and the ESA’s Planck mission. The Planck satellite, you may recall from reading here or elsewhere, is also designed to
carefully study the polarisation of the cosmic microwave background (the earliest light to shine in the universe), and so can (through thorough analysis of the effects of dust that it has measured independently) help rule in or out whether there is a signal. Planck studies essentially the whole sky, not just the patch that BICEP2 was carefully looking at, and 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
Happy New Year! So, it is the second of January. You’ve spent all of the day yesterday recovering from the euphoria (and perhaps revelry) of New Year’s Eve, and so today it is time for the traditional next thing on the new calendar: Planning what you’ll do next New Year’s Eve, of course!
Before doing that however, if you are a research physicist, I’d like to invite you to consider doing something else: Plan your Summer research travel. What I am really trying to do is to make you aware that the end of this month is the deadline for applying to attend the Aspen Center for Physics during some period inside the Summer operating dates Memorial Day (in May) to around Labor Day (September). Now, a lot of people (too many, in my and the opinion of others who care about the ACP) just assume that the place is not for them, for a number of reasons that are really not good ones. So let me address one or two quickly right now.
First, it is not an old boy’s country club. It is for everyone, working in all* fields of physics. Don’t apply and you have zero chance of getting in. Apply and there is […] 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
The UCLA group is hosting the next Southern California String Seminar, the long running once a semester (mostly) regional event that roves around the various high energy groups in the region (more here). It is on Friday!
There’s schedule and other information here. The schedule goes something like this: […] Click to continue reading this post
I’m a fan of Chris Nolan’s work so I’ve been looking forward to Interstellar. I’ve also been fascinated by the McConaussance – the transformation of Matthew McConaughey into an actor of considerable stature in a series of excellent films (Mud, Dallas Buyers Club, etc…), so I’ve been doubly interested in seeing how he works in a film under Nolan’s direction. Same for the always amazing Casey Affleck. All quite exciting to see.
But then to my surprise it turns out there’s another reason to be interested. Kip Thorne. Some years ago, at a party when I last saw him, Kip told me that he had been working on some film or other with a major studio, but I did not know of the details. Then I ran into a mutual friend a couple of months ago who said something a long the lines of “Kip’s movie is coming out soon…”, and I learned that it was something to do with Interstellar! But I did not know any details.
Then I got sent* this Wired story, and then** this story, and I finally got around to looking. The Wired story has a lot of interesting detail, including a special film (that I ought to look at at) with interviews and behind the scenes material (the still to the right is a screen shot from it). 
The film will apparently feature a black hole and a wormhole in some way (I don’t want to know more – I like films to unfold in front of me in the theatre). Kip has been working with the visual effects people to get right exactly how such objects really look, an issue that has not really been fully addressed, it seems. He, like a number of us interested in science and film, is keen to help filmmakers really do a good job of representing some of these fascinating objects as accurately as possible. (Not, in my view, in order to stifle filmmakers’ imagination, as it so often seems when you hear scientists out there pontificating about what’s wrong in one film or another, but because the actual science is so very often far more interesting and full of delights and possibility than a visual effects kluge can be…) So apparently he wrote down […] Click to continue reading this post
I’m on the road. I gave a seminar at the University of Michigan yesterday, and spent the working day chatting with various physicists at the department there, exchanging ideas, catching up on what people are up to, etc. The seminar itself went ok. I’ve been talking about extended gravitational thermodynamics, the subject of all my papers so far this year. I think I paced things a bit poorly (trying to squeeze in results from two papers while at the same time being pedagogical about the basic material since it is not familiar to most), so had to rush at the end, but I got the main points in. Lots of good questions.
At the end of the day, I was pleasantly surprised by the offer of whiskey in the break room. Apparently it is a Friday tradition. I began to wonder, and made some inquiries and found out to my delight that it is a direct decendant of a tradition that I (co-) started back in the mid-90s in Santa Barbara!
It was a long time ago, so I am hazy on who the core people were who regularly kept […] Click to continue reading this post
There has been quite a bit of discussion of the realisation that the exciting announcement made by the BICEP2 experiment back in March (see my post here) was based on erroneous analysis. (In brief, various people began to realise that most, if not all, of what they observed could be explained in terms of something more mundane than quantum spacetime fluctuations in the ultra-early universe – the subtle effects of galactic dust. A recent announcement by another experiment, the Planck team, have quantified that a lot.)
While there has been a bit of press coverage of the more sober realisations (see a nice June post on NPR’s blog here), it is (as with previous such cases) nowhere near as high profile as the initial media blitz of March, for better or worse. I think that “worse” might be the case here, since it is important to communicate to the public (in a healthy way) that science is an ongoing process of discovery, verification, and checking and re-checking by various independent teams and individuals. It is a collective effort, with many voices and the decentralised ever-sceptical scientific process itself, however long it takes, ultimately building and broadening the knowledge base. This self-checking by the community, this reliance on independent confirmation of […] Click to continue reading this post
So while at a hotel somewhere down South for a few days (pen and watercolour pencil sketch on the right), I finally found time to sit and read Graham Farmelo’s book “The Strangest Man”, a biography of Dirac. (It has a longer subtitle as well, but the book is way over in the next room far from my cosy spot…) You may know from reading here (or maybe even have guessed) that if I were to list a few of my favourite 20th century physicists, in terms of the work they did and their approach and temperament, Dirac would be a strong contender for being at the top of the list. I am not a fan of the loudmouth and limelight-seeking school of doing physics that seems all so popular, and I much prefer the approach of quietly chipping away at interesting (not always fashionable) problems to see what might turn up, guided by a mixture of physical intuition, aesthetics, and a bit of pattern-spotting. It works, as Dirac showed time and again.
I’ve read a lot about Dirac over the years, and was, especially in view of the title of the book, a little wary of reading the book when I got it four years ago, as I am not a fan of going for the “weren’t they weird?” approach to biographies of scientists since they serve too […] Click to continue reading this post
I thought I’d mentioned this already, but I could not find anything after a search on the blog so somehow I think I must have forgotten to. It is a cute thing about a certain favourite solution (or class of solutions) of Einstein’s equations that I’ve talked about here before. I’m talking about the Taub-NUT solution (and its cousin, Taub-Bolt). Taub-NUT is sort of interesting for lots of reasons. Many, in fact. One of them concerns it having both mass [tex]M[/tex] and another parameter called “nut charge”, [tex]N[/tex]. There are several ways to think about what nut charge is, but one curious way is that is is sort of a “magnetic” counterpart to the ordinary mass, which can be thought of as an “electric” quantity.
The language is based on analogy with electromagnetism, where, in the usual […] 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
As you may know from three previous recent posts on research (here, here, and here), I’ve been thinking and calculating a lot in the area of dynamical cosmological constant – concerning mostly (but not entirely) thermodynamics and quantum gravity. Specifically, the cosmological constant becomes the pressure variable in the thermodynamics. I think it is important, and will teach us something about things like gauge/gravity duality, string theory, black holes, and perhaps even cosmology, but I am not sure what yet. I’ve made some suggestions in recent papers, and computed some interesting things along the way.
Anyway, the larger community has not been following this story much, since: (1) It means a break with some powerful and still very fruitful frameworks where the cosmological constant being fixed is a given – like AdS/CFT – and it is not clear what that means yet, so the motivation is not super-strong; and (2) Let’s be honest, there’s no superstar working on it, so it is not going to get anyone any points. So I’ve been trying to shout about it in my little way from the periphery, as I think it might be useful, and since several people have been doing really good and interesting work on this issue for many years and it is worth more people seeing what they’ve been up to.
So imagine my pleasant surprise when I looked on the listing of new papers on the arXiv for today and saw three (!) papers on the subject, moving things forward in various ways. (They all seem to have noticed some of what I’ve […] Click to continue reading this post
