…more to go. I’ve finished one of the papers I’ve been writing (this one co-authored with my student, Tameem) after delaying on it for months. I’m not sure how things got quite this backed up in terms of things I have to do, but they have. I meant to start on a new, long project last week, and all my efforts these days have been toward clearing away all those things I want to get done and dusted before focusing on that. It is taking time, but gradually the clearing is happening. Two more manuscripts to complete.
This paper reports on the continuation of the work we’ve been doing over the years in understanding the physics of various model systems in an applied magnetic field. This is in the context of holographic models of important strongly coupled phenomena that are of considerable interest in lots of fields of physics (particle physics, nuclear physics, condensed matter physics, atomic physics). (Since I don’t want to explain holography and so forth every time I talk about it, see a post I did about some of that here, and related posts in the list at the bottom of this one, if not sure what I’m talking about.) (Hmmmm, I see from my SPIRES listing that I’ve got seven papers mentioning magnetic field explicitly in the title in the last three years, and three or four more of the rest are occupied in large part with the issue too. No, really, I’m not obsessed.)
The issue here is the study of structures that suggest themselves as earmarks of Fermi surfaces in strongly coupled systems. It has been a goal for a long time in the context of gauge/gravity duals to understand what the signals of a Fermi surface would be. Would it be some geometrical object in the dual gravity theory, perhaps? Access to a computationally tractable description of such an object would be rather […] Click to continue reading this post
I’ve been wondering why over the last day or two I’ve been getting email about various apocalyptic scenarios. I’ve now figured out why, I think. On Tuesday, several scientists, myself included, played with the idea of how to destroy the earth! Well, it was on the History Channel in an episode of the show the Universe, (it was recorded back in June and July) entitled “Ten Ways to Destroy the Earth”. Of course, these are not scenarios we envision happening any time soon, but rather an excuse to talk about various kinds of science (from spontaneous symmetry breaking and the early universe, through planetary science, solar physics, and of course black holes and more). We list various favourite ways that were chosen to be discussed, and each physicist (although they called me an astrophysicist) picks a favourite. Fun stuff.
I chose putting a huge amount of antimatter at the core of the earth and letting it […] Click to continue reading this post
Well, ok… Boom is not quite accurate, but the idea is that there will be ten kinds of blasts/explosions/major_energetic_events discussed tonight on the History Channel’s The Universe:
The Universe is full of explosions that both create and destroy. The Chicxulub impact on the Yucatan peninsula, which may have wiped out the dinosaurs 65 million years ago, was two million times more powerful than the largest nuclear bomb ever detonated on Earth. But guess what? That’s only good enough for the very bottom of the Biggest Blasts top ten list. This episode works its way up through supernova explosions and gamma ray bursts all the way to the blast that started it all–the Big Bang.
Sounds good doesn’t it? There’s a lot of good people contributing again, so I know it’ll have some good material and explanations.
In addition, I’m reasonably confident I play a role in this one…This one was a blast (sorry) to film. You saw some posts earlier reporting on some of the filming. Assuming they used the material I did with them, you’ll get to see why I was at the […] Click to continue reading this post
Forgot to report on this email exchange from last semester:
From one of the staff in the physics office:
Subject: 499 Syllabus
Date: Thu, 09 Jul 2009 14:01:38 -0700
To: Clifford V. Johnson
I was reading the syllabus you sent over for the 499 class. I am not sure if this is a type-o but in the Extra Books section it reads “/Black *_hoes_* and Time Warps: Einstein’s outrageous Legacy/” should it read
“/Black *_holes_* and Time Warps: Einstein’s outrageous Legacy/”.
My response: […] Click to continue reading this post
The College of Letters, Arts, and Sciences here at USC has built a new website, and gone quite far in including extra media, and links and portals on YouTube, Facebook and so on. One of the things they did was have a filmmaker make lots of videos. Lots. Things about faculty, research, teaching, learning, etc. All very exciting. Have a look, here, if interested. Mira Zimet, who makes the films, gave me a call and asked me if I’d like to contribute, and I agreed. I chatted on and on for about 45 minutes to an hour and she cut two short films out of it. The shorter one is on the site and has me saying some general things about research, teaching, science, and USC. Mira made the second because she thought it might be a nice extra video for the College’s YouTube portal. It has me talking a bit more about what string theory is and does, […] Click to continue reading this post
Ironically, the day after earth day, a TV program (part of the Naked Science series) entitled ‘How to Kill a Planet’ will air tonight (Thursday 23rd April) at 10pm on National Geographic Channel. It explores various scenarios for how the entire planet could be destroyed. Sensational, yes, but maybe an interesting way of exploring some interesting physics topics in an unusual way, assuming they don’t scare people unduly. I appear in it somewhere, I’m told. I’ll be talking about black holes, and may in fact be shown being swallowed by one, if I recall correctly what was planned. Some may rather enjoy that aspect! [Update: Phil’s on it too!]
You may recall me mentioning a shoot I did up near a dry lake (El Mirage) in the […] Click to continue reading this post
Well, the last couple of days events were tiring, but good overall. The Hawking event was a bit like a rock concert. I made a video of some of the long line for you, and also take you into Bovard Auditorium with me to see the rather nicely packed crowd (well the downstairs part) of about 1200 excited audience members. At the end of the video are a few stills, showing Dean Howard Gillman during his welcoming remarks to the College Commons event, Nick Warner introducing Stephen Hawking, the man himself, and some of the high school students and the undergraduate student, who won the prize to get to ask Stephen questions. (The high school students had all asked similar questions, and so were all asked up to ask one question.)
Here’s the video: […] Click to continue reading this post
Gosh, time flies!
I almost did not get to announce this before it was upon us. Tomorrow and the day after combine into a notable event in the College Commons series here at USC. Some of us have been working on this for quite a while. On Tuesday we have Stephen Hawking giving a big public lecture entitled “Out of a Black Hole”. Here’s the announcement. Note that general tickets for seats in Bovard Auditorium all went within hours of us releasing the tickets several weeks ago, but there is room in the two spill rooms that we have set up where there will be screens relaying the talk. Make a bit of an event of it and go with friends! [Update: I forgot to mention that we had a competition in local high schools and also at USC where the prize was to ask Stephen Hawking a question. People submitted questions over the last few weeks and we selected some of the best. There will be three undergraduates and three high school students coming up from the audience (we’ve a lot of high school students visiting us for the talk) to ask him a question each at the end. Should be fun.]
The day after, there will be a related event. Some of us from the physics department […] Click to continue reading this post
The usual answer you’ll get from the person on the street (as it were) includes lots of nice words about wiggling strings that look like particles, and so forth, and that’s fine. However, the [
informed] next level answer, when you’ve worked enough in the field, is that we don’t know. I’ve told you why (at least in part) in previous posts and so I’ll let you read them. We’re still working on it.
While we work, we’ve learned that it is a quite marvellous thing (from the bits of it we’ve come to grips with) that is teaching us a lot about all kinds of physics, and mathematics too. Some of this may be good for describing things about Nature, and we’re still working out lots of that (although see some of the exciting things I’ve been talking about in my previous post and the links therein).
So what do we put on the T-shirt? (You know, the analogue of Maxwell’s equations for electromagnetism – light, etc – that every physics undergrad likes to have on their T-shirt). Well, we don’t know yet.
But that’s all my opinion. Every now and again it is good to hear from one of the masters about what they think of string theory*, and what it is and so forth. Happily, Joe Polchinski has been known to agree to stand up and give an exposition on this […] Click to continue reading this post
I had quite a marvellous brainstorming session today. You’ll recall I was preparing a presentation for the February 15th symposium at the AAAS meeting the other day. Well, all of us concerned (the four of us presenting as well as various Brookhaven staff who will take part in the symposium discussion as well) got together over the phone for a teleconference today. It took almost three hours (but happily I was sitting in the sunshine while doing it, as you can see). We wanted to chat about the distribution of ideas and results that will be presented.
There are four of us presenting at the event, with only a short time each to get across some of the key ideas and so we need to make sure that we don’t do too much […] Click to continue reading this post
I noticed that Robert Helling shared some thoughts about thermodynamics and gravity today on his blog. He is understandably confused about several aspects of the issue, especially when applied to cosmological issues. (What is the entropy of our universe? Does the Second Law really apply? Does equilibrium thermodynamics even apply here?)
I’ve nothing remarkable to add to the discussion at this time except to note that a blanket statement that thermodynamics and gravity don’t seem to go together (which I don’t think he’s strongly saying) is not one I’d make, since we have a major class of working counterexamples.
The context is the gauge/gravity duals I’ve talked about here a lot, starting with AdS/CFT and beyond. There we know that the gravitational systems are essentially able to display the more garden variety thermodynamics by being immersed in the (regulating-box-like) anti-De Sitter type backgrounds. Then we see that black holes […] Click to continue reading this post
Some reflections over breakfast – at least breakfast part II. Well, elevenses, really. Today is, I hope, a day to spend mostly on thinking about research issues. There’s a project I’m still unhappy with, in terms of where I’d like it to be, and I want to try to move things on. I had a new idea on the bus yesterday that I’ll be testing out today. Since I’m giving a seminar about this project on Friday, I’d also rather like to get it all uploaded back into the more active buffers of my brain, as it were.
Tuesday is a welcome day, being between my two biggest teaching days of the week, days that usually completely drain me. I try to use it to remind myself that I’ve a ton of other activities besides teaching that I should be getting on with. Research is one of them.
This morning began with something else, however, and I thought I’d update you on […] Click to continue reading this post
Well, the new orbiting instrument, GLAST (Gamma-ray Large Area Space Telescope – launched June 11th this year) has passed all its tests with flying colours, apparently, and is working well. NASA has now renamed the craft the Fermi Gamma-ray Space Telescope, after Enrico Fermi. There’s a press release here.
The craft is a wonderful combination of the fields of particle physics, astrophysics and cosmology, and will teach us so much about the universe (such as the nature of dark matter), and so it is exciting to hear that it all on track.
Excitingly, they’ve also released images of the early results of the observations, and you can read more about them in the press release too. Here’s a sky map made from the observations.
This all-sky view from GLAST reveals bright emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes. Credit: NASA/DOE/International LAT Team.
Some words from the release: […] Click to continue reading this post
I just happened (while flicking channels to try to avoid the
naked mud-wrestling, oops, women’s beach volleyball*) to run into a broadcast of the Los Angeles Public Library conversation between KC Cole and Lenny Susskind about the amusingly titled “Black Hole War” between him and Stephen Hawking and the circle of ideas and theories connected with all of that wonderful area of physics. (I blogged about it here and here.) It looks like it was really good (I just caught some of the questions and answer […] Click to continue reading this post
Well, you may not have gone to the chat between K C Cole and Leonard Susskind that I mentioned a while ago at the LA Central Library downtown. I couldn’t make it either, being away at the Aspen Center for Physics. I expect it was good. Anyway, I found a little bit of a report on the conversation, done by reporter John Johnson for the LA Times. It is here. (Clickable image of Susskind to the right is by Matthew Black, for the LA Times.)
It gives you some of the simply-stated reasons as to why there was a big argument between Stephen Hawking and Leonard Susskind in the first place (and between several other physicists too… there are hosts of people working on these things, and it took hosts of people to sort it out to where we are now, not just those two, giants though they are). I recommend having a look, as it is especially for the lay-person, and will give you a good idea of what the fuss is about.
You can also see a little bit about his new book on the subject and a link to a video interview with Brian Cox (the physicist, not the actor) at the LA Times blogs here. There are also links to his Stanford continuing education course on quantum mechanics, including the online lectures you can view at your convenience. What a resource!
You might wonder why we care about all this, since currently the only way we know for sure to make black holes in the universe (astrophysical processes making stellar black […] Click to continue reading this post