Harmonics Can Make Metals Flux

I’m sitting on the bus, on my way to the LA Times Festival of Books. I’ve opened my notebook to maybe sketch a face or two, but then I spot an algebraic error on a page from a few days ago, so I set about correcting it….(you know, either for those historians who will argue about my intentions while poring over these once-lost manuscripts…. Or more likely for me in a few weeks, likely to get confused by my own blunder-in-haste with a kindergarten level variation.)

20140412-122335.jpgA bearded fellow had boarded the bus and sat next to me while I was doing this. He eventually glances my way, then away, then he does a double take. I’ve been watching him out of the corner of my eye. He starts to speak to me.

Calc or Trig?
Excuse me?
Calc or trig?
Er…. Physics.
What are you studying?
I’m not…studying. It is my research.

Silence from him for a few beats, then:

Into what?
Charged black holes.

I should say at this point that I get this a lot. No matter who I meet out there in the random world, or what they see me writing, the assumption is always that I am taking a class in high school mathematics. Why is that? People, at least guess for some of the time that I might be at least teaching it, even if you can’t imagine people doing research in this area. The grey hairs in my beard are a guide to your assumptions.

Another gripe: if you see someone writing words, and want to engage them in conversation about it, you don’t assume they are practicing the basic structures… Imagine the analogous exchange: Are you practicing joined-up writing madam, or spelling? Neither, I’m writing poetry.

Anyway, back to the conversation. So, as you recall, I said Charged black [...] Click to continue reading this post

Exam Heat

We had a midterm in the undergraduate General Relativity class this week. Midterm II. We’d just come off a batch of lectures on black holes (focussing on Schwarzschild and Kerr), and so it seemed very natural to focus on that as the topic. Schwarzschild is the most basic (vanilla) black hole and Kerr is the case of having rotation for a bit of extra flavour. They are both hugely important in real physics – the former for the basic phenomena and then the latter since most objects out there in the astrophysical realm are actually going to be rotating to some degree (and after gravitational collapse, probably a high degree). So I focussed on those in class.

Screen Shot 2014-04-11 at 14.45.37For the midterm therefore, I got the opportunity to have them discover properties of the (less astrophysically important perhaps) charged black hole – the Reissner-Nordstrøm solution:
 ds^2=-\left(1-\frac{2M}{r}+\frac{Q^2}{r^2}\right)dt^2+\left(1-\frac{2M}{r}+\frac{Q^2}{r^2}\right)^{-1}dr^2+r^2\left(d\theta^2+\sin^2\theta d\phi^2\right)\ ,

…and do a few computations with it analogous to what they did for the other cases in class and in homework. I hope they had fun (like discovering that for a [...] Click to continue reading this post

Wormholes!

“So, you have a choice. We’ve ten minutes of class left. I can either finish early, or…. I can show you that there’s actually a wormhole living in this picture, or can I tell you about Hawking radiation.”

wormhole_sketchThat was the choice I presented the students with after we’d spent some time together exploring the Kruskal-Szekeres extension the the basic black hole solution, in my General Relativity class today. You probably don’t know what all that is, and that’s ok. Suffice to say that you end up with a pretty diagram which looks like two everlasting black holes put together as in a sort of elegant trading card. Or perhaps a neat knot where one black hole is sort of upside down and neatly slots into the other one so that they hug each other into eternity, acting as each others’ past and future. Look it up and see.

Anyway, they went for the wormhole, with a chant “Worm-Hole! Worm-Hole!”. So I constructed the wormhole for them… the Einstein-Rosen bridge, as it is known, ending with the sad news that it is not a real traversable wormhole that [...] Click to continue reading this post

Hawking an Old Idea

On the one hand it is good to get members of the general public excited about scientific research, and so having some new excitement about something Stephen Hawking said, driven by gushingly written articles in the press and online, can be good. On the other hand, it is annoying that the thrust of the articles are largely that he’s stunned the world again with a brilliant and unlooked-for idea. People just lap this stuff up, unquestioningly. It is actually an old idea (and in fact one that is being mis-reported – see below). One’s instinct is to just say “Welcome, Stephen, we’ve been waiting for you to join us”, or “Come on in, the water’s lovely”, and just move on, but it seems so unfair. The thing that’s most puzzling in all of this is Hawking’s own paper (which is all of two pages of words – a transcript of a talk he gave in August), which makes no reference at all to (for example) Samir Mathur’s work, which has been explicitly saying essentially the same thing for well over a decade, with a very definite proposal for how it might work. That work has hardly been buried in obscurity. Samir and many other people who have liked his idea have been working out the consequences of the proposal in numerous papers for over a decade and reporting on their results at all the main conferences, and even talking to him about it (I note that Samir was in the audience during the August talk and even politely asked the speaker to compare and contrast the similar-sounding proposals). So it is puzzling that you get no hint from the paper’s citations that this is a well-considered and ongoing idea, even if (perhaps) in detail it may pan out differently from other suggestions.

light cones in  spacetime with a compact mass - a black holeWhat’s the idea?, you ask. Well, it is not, as you might get from most of the articles (somewhat confusingly), that black holes do not exist. It is that the black hole’s event horizon, thought of as a sharp “point of no return” boundary, may not exist. Instead, it is approximation or shorthand for the complicated physics (of both matter and spacetime) that happens in the vicinity of the black hole. Simply put, the horizon arises in classical solutions to classical (i.e. non-quantum) equations (such as in General Relativity) of gravity. (See an earlier post I did about them here, from which came the illustration [...] Click to continue reading this post

Ten Things…

black_hole_phil_club_talkSo I’ve been a bit quiet as I’ve had a lot going on. This includes preparing ten interesting slides to use as props for a talk I gave this evening to the USC Philosophy Club. It was entitled “Ten Things YOU Should Know About Black Holes”. It started with the original idea by Michell in 1783 (yes, really, that early!) and ended with topics of current research (what is the fate of the singularity? What really happens at a horizon? Etc., etc…) I spoke for a while and then fielded tons of questions, and am now (I am writing a draft of this on the subway train home – uploading later) suffering from a rather broken voice due to too much talking and projection…. Gosh. But it was fun. A really […] Click to continue reading this post

News from the Front, X: Smoother Transition

second_order_transition_1Yesterday I submitted a new paper to the arxiv. This is is my favourite curve from it. Some of you who follow the blog will recognize the blue circle-dots and guess that this is the output of the dot-generation I’ve been tinkering away at (and reporting on somewhat cryptically) since April (see e.g. here, here, and here). Correct. There are many reasons why that is the case. One of them might well be because it looks like a very comfy chair, and by time I’d submitted the paper, I was rather tired. I’d pulled an all-nighter to finish the paper because I wanted to submit it by noon yesterday, and the night before I had to spend several hours at a social event.

So once it was an appropriate time to leave the place I was at, I said my goodbyes, jumped on my bike, pedalled home, all_nighter_things put on some coffee, some Ana Tijoux (through headphones, so as not to wake anyone. Why her? Kinetic energy was what I needed at that moment – her vocal style is full of that. Try “La Bala” or “1977″. It is in Spanish, but that’s just fine.), and from 10:30pm to about 12 hours later, ground out the paper. I had to do this since I took some time away from the research project for a week, and then on Tuesday evening noticed the title and abstract of a new paper on the arxiv that suggested some overlap with what I was doing. So I had no choice but to gather all the results I’d been gathering the last several weeks and write them up and get them out, putting off reading the other paper until afterwards, so as to remain independent. Hence the all-nighter to finish it all. It was a pretty easy paper to write since I’ve had the results for a while, knew what I wanted to say, and it was just a matter of pulling everything together and writing a lot of background to set the scene for the results. A fair amount of the time was spent fiddling with things like how to generate figures from Matlab that embed nicely into the text, and so forth. Technical tedium.

The physics? Another reason I like the above curve is because it examines physics from an old favourite phase transition I co-discovered almost 14 – gosh yes, cvj, fourteen! – years ago. To my knowledge it is perhaps the earliest example of a [...] Click to continue reading this post

TED Youth Talk – Hidden Structures of the Universe

cvj_TED_YouthYou might recall that last year I gave a talk at TED Youth, in their second year of short TED talks aimed at younger audiences. You’ll recall (see e.g. here and here) I made a special set of slides for it, composed from hundreds of my drawings to make it all in graphic novel style, and somehow trying to do (in 7 minutes!!) what the TED people wanted.

They wanted an explanation of string theory, but when I learned that telescopesI was the only person in the event talking about physics, I kind of insisted that (in a year when we’d discovered the Higgs boson especially!) I talk more broadly about the broader quest to understand what the world is made of, leaving a brief mention of string magnifytheory at the end as one of the possible next steps being worked on. Well, they’ve now edited it all together and made it into one of the lessons on the TED Ed site, and so you can look at it. Show it to friends, young and old, and remember that it is ok if you don’t get everything that is said… it is meant to invite you to find out more on your own. Also, as you see fit, use the pause button, scroll back, etc… to get the most out of the narrative.

I’m reasonably pleased with the outcome, except for one thing. WHY am I rocking [...] Click to continue reading this post

Tales from the Industry XXXIX – Magnetic Weather?

Today (Tuesday) saw me up at 6:30am to prepare for an 8:00am call time for a shoot on a special episode of – wait for it – Deadliest Space Weather. It is original programming for the Weather channel, and before you dismiss it because of the title, it turns out that it is not a bad idea for exploring various scientific concepts. The first season ended a few weeks ago. I’d not realized it was airing until recently, and actually those recent demos I told you about were used in examinations of planetary conditions on Venus and on Mars. (Two separate episodes.) The idea seems to be to consider what it would be like on earth if the conditions were like those on Venus, or consider what what happen if you went outdoors on Mars.

So you might think it is silly, but if done well, it is actually an opportunity to
explain some science to an audience who might not have been the usual science audience…in which case I’m happy to be on board! In addition to spectacularly showing what happens when sugar and sulphuric acid meet, I got to show how to boil [...] Click to continue reading this post

Minority Report

This is a quick update on the school. I’ve been trying to give the students some of the core concepts they need to help them understand what string theory is, how it works, and what you can do with it. Here’s the really odd thing about all this (and an explanation of the post title): While this is a school on Quantum Gravity, after talking with the students for a while one learns that in most cases the little they’ve heard about string theory is often essentially over 20 years out of date and almost always totally skewed to the negative, to the extent that many of them are under the impression that string theory has nothing to do with quantum gravity at all! It is totally bizarre, and I suspect it is largely a result of things that are said and passed around within their research community.. So there [...] Click to continue reading this post

News From The Front, VIII: One Down…

work_snap…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

Doomsday Fun and Games

the_universeI’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

Ten Things That Go Boom!

the_universeWell, 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

Oops!

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
From: Beverly
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/”.

Thanks,

My response: [...] Click to continue reading this post

Scenes from Work

cvj_at_workThe 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

Killing the Earth

el_mirage_shootIronically, 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

Waiting for Stephen

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

Hawking Talking, and More

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

So What Is String Theory, Anyway?

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.

polchinski what is string theory

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

Brainstorming

presentation preparation in the sunI 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

Thermodynamics and Gravity

ads_ballI 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

Breakfast Babble

breakfast thingsSome 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

GLAST, Fermi, and Early Results

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.

glast-sky_map-08_24_08

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

Susskind and Cole on C-Span2

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

Quantum Black Holes – Why Worry?

susskind_by_matthew_black for LA TimesWell, 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

Black Hole Battles

lenny susskind, kc coleSomehow, I only learned about this today, and it is already standby tickets only, but you never know. If you’re in LA and interested in a different kind of conversation, consider taking in the event (part of the Aloud series) at the downtown Los Angeles Central Library tomorrow night at 7:00pm. It’s between two friends and colleagues of mine, the science writer K C Cole and the scientist Lenny Susskind! The event is entitled, “The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics”, and presumably will be about Lenny’s reflections on some of the exciting squabbles over various important issues in black hole physics that took place (and still take place) in our field of physics. The above turns out to be (I just learned from a Google search) the title of a book he’s written, so you might be interested in it for your Summer (or other) reading.

Some of you may recall her really great conversation with Alan Alda that took place at USC earlier this year. I reported on it here. K C tends to run these sorts of [...] Click to continue reading this post

At Last – GLAST!

GLAST launch in progressGood news everyone! GLAST has been launched successfully. GLAST stands for Gamma-ray Large Area Space Telescope, and it does exactly what it says on the packet. It is an instrument designed to look more closely at gamma rays from outer space. More here. It will help (alongside other instruments such as SWIFT) get better understanding of a wide range of gamma-ray emitting objects, that pertain to a wide range of issues, astrophysical to cosmological.

“Gamma ray bursters” are obvious super-powerful sources of gamma rays out there, largely due to macroscopic astrophysical objects (collapsed stars or stars in the process of doing so, or merging with each other – see earlier posts) doing violent things, or interacting violently with their surroundings. So are active galactic nuclei, powered by black holes. We’d like to better understand all of the processes that allow these objects to generate gamma rays.

Other sources could include particles and antiparticles annihilating each other and (by [...] Click to continue reading this post

Some Unusual Recipes

Quark  Gluon Plasma RecipesWell, I’ve been quiet here because I got rather swamped with lots of things over the last few days. The biggest thing was yesterday. I gave a colloquium at Caltech entitled “Cooking with Quarks and Gluons: Recipes from the String Theory Kitchen”. The abstract is given below. It is mostly based on what I wrote about last Summer.

With all the other things I had to do (including writing and giving two fun two hour lectures on cosmology in my undergraduate GR class) I still decided that it was time to totally rethink how I tell this exciting physics story, and how I present it. This meant designing and building many new slides. Each slide can take a long time to prepare, so this took two solid days of hiding away while designing and building them, only breaking for the other stuff.

Well, it was fun in the end, and today I am exhausted. I decided that you should not miss out entirely on the treats, so I made a little movie of the first parts of the talk to [...] Click to continue reading this post

So What Are the Odds?

John Howe’s Glorund vs Turin imageWell, I’ve said (and pointed to) enough on the matter, but I could not resist a quote from today’s essay by Dennis Overbye in the New York Times (do have a look at the rest of it):

Besides, the random nature of quantum physics means that there is always a minuscule, but nonzero, chance of anything occurring, including that the new collider could spit out man-eating dragons.

Excellent! Proper flying, armoured, fire-breathing, talking, treasure-hoarding, [...] Click to continue reading this post

All Creatures Great and Small

The previous post was a farewell to black holes in the class, not here on the blog. (And it was not quite a farewell there either, since the midterm yesterday was all about the properties of the Reissner-Nordstrom black hole, representing a black hole with an electric charge, and a nice computation involving cosmic censorship.)

There have been two rather notable discoveries in the black hole astrophysics world this week. The first is the discovery of what seems to be another case of an intermediate mass black hole (there was only one example known before). Not the supermassive ones that live at the centers of galaxies (tens to hundreds of millions of times the mass of our sun), and not stellar mass ones of a few times the mass of our [...] Click to continue reading this post

A Farewell to Black Holes

Yesterday here at USC was my last lecture in the class about black holes (see also here). We’ve got to move on to other topics (Cosmology, Einstein’s equations, etc) and so cannot do any more. It was a fun last lecture though. I pulled together a few scraps of things I did not finish in the previous lecture (such as the extraordinarily high percentage of binding energy per unit rest mass you can extract with rotating black hole orbits – just what you need to power things like quasars) and then finished with:

  1. A taste of Hawking radiation, the Bekenstein-Hawking entropy and the wonderful and beautiful subject of black hole thermodynamics that opens up when you combine gravity with quantum mechanics*, followed by…
  2. A quick discussion of the Penrose process for extracting energy from rotating black holes. (I’m sure that all (past, present or future) super-advanced civilizations must be using them as the ultimate emissions-free means of generating energy for heating their homes and so forth. No, really.)

*Of course, all undergraduates commonly hate it when you dare bring in stuff from other classes, so to [...] Click to continue reading this post

More Trouble for LHC?

[Update:- NB: This was an April Fool joke. -cvj]

CMS detector - New York TimesSome breaking news for a change. I’ve only heard snippets of this and so I’ll update later with more as I get it. That silliness that was in the news about two physicists pursuing a lawsuit against the Large Hadron Collider has suddenly become serious. (Image right: the CMS detector at the LHC, taken by Valerio Mezzanotti – from a NYT article last year.)

Recall that the issue was that there would be the possibility of the experiment creating mini black holes that could gobble up the earth and that the CERN scientists have not done enough to demonstrate that this was not a safety issue. Of course, and has already been said in several places (see e.g., Phil’s general level post about the physics and the case here), this is utterly ill-conceived and in any case certainly not the way to go about things, but it seems that the legal route can be quite damaging for science, in the right hands.

What seems to have happened is this. Since the suit was filed in Hawaii, it falls under US Federal jurisdiction, and has been taken up as an emergency issue before the Supreme Court. Somehow the litigants got a hearing on this with the help of powerful friends who have what can only be thought of as another example of the anti-science agenda we’ve a lot of in various branches of the government in recent years.

The upshot is that the Supreme Court has announced today that they are requiring all [...] Click to continue reading this post

Law Vs Law

A silly lawsuit vs the search for physical law, that is. What’s the story?* An attempt to stop the Large Hadron Collider (LHC) in Geneva from operating over fears that the experiment will destroy the earth by creating a black hole that will swallow it up. Or some other bogeyman. Article by Dennis Overbye here, or here, and there’s a Fox News story by Paul Wagenseilhere.

The lawsuit, filed March 21 in Federal District Court, in Honolulu, seeks a temporary restraining order prohibiting CERN from proceeding with the accelerator until it has produced a safety report and an environmental assessment. It names the federal Department of Energy, the Fermi National Accelerator Laboratory, the National Science Foundation and CERN as defendants.

Quite an entertaining read can also be found at the two plaintiffs’ website. The main [...] Click to continue reading this post

Bigger than the FCC

We’ve been studying rotating black holes in my class this week, which has been fun. We get to apply the techniques we’ve been honing in the context of the Schwarzschild solution (link to recent posts below) to a bit more complicated solution, the Kerr solution, which includes rotation. Some equations follow, although you needn’t be put off by them. Most of this will make sense without really understanding them much. Just so you can see the shape of the things we scribble, I’ll show you the equation that captures this curved spacetime geometry, with no real explanation (sorry):

kerr solution

Here \Delta\equiv r^2-2Mr+a^2 and \rho^2\equiv r^2+a^2\cos^2\theta\ . The parameter a is the ratio of the solution’s spin or angular momentum J to its total mass M, measured in appropriate units. It’s a very important solution to get to grips with, since it’s not just fantasy physics, but highly relevant for astrophysics since black holes that are “out there” are unlikely to be non-rotating, and in fact, one can expect them to be rotating at quite a clip in many cases. A good many black holes – including some of the [...] Click to continue reading this post

Tipping the Light Cone: Black Holes

Black Holes by Tamsin Van Essen: http://www.vanessendesign.com/

Black Holes, by Tamsin Van Essen. Part of a series of lovely ceramics with a physics theme. For more, visit the websites here and here.

As you may recall from the post I did some time ago, the “Light Cone” is a rather important concept in physics, and keeping track of it in a given physical scenario is an extremely important tool and technique for understanding many physical situations. (I urge you to review that post before continuing reading this one.)

One way to understand a most important concept – the event horizon – is by keeping track of lightcones, and so let’s go ahead and explore that here. The outcome is that [...] Click to continue reading this post

Beyond Einstein: Fixing Singularities in Spacetime

Not long ago David Morrison (UCSB) came to the mathematics department here at USC to give a colloquium.

David Morrison Colloquium at USC

This was a treat for me for many reasons. Here are three:

  1. It’s always good to see Dave. He’s one of the people I’ve known in the field was since my very first postdoc when I was learning to survive in the big bad world on my own after graduate school. I mostly could not understand a word he or anyone there else said in those days (IAS Princeton, right in the belly of the

[...] Click to continue reading this post

The Universe Tomorrow

Over on Correlations, I talked a bit about the History Channel’s science show “The Universe” (as I have here), and pointed out that the new season (season two) has already begun being broadcast. Here’s hoping that it’s a good series of programmes that will be enjoyable and informative. The show’s website is here.

Well, I’ve learned that the second episode, tomorrow’s (showing at 9:00pm), is one of those that i did some shooting for over the last two months at a number of places around LA. Rather than repeat, here’s what I said:

The next one, to air on Tuesday the 4th December, is called “Cosmic Holes” (yeah, I know), and the subject matter will be right on the edge of the known and the unknown, talking about black holes, white holes, and wormholes. While we know that the first are out there, the second two, while also solutions of Einstein’s General Relativity, are still theoretical constructs (and not without problems). The show explores some of the ideas and the prospects for the ideas surrounding

[...] Click to continue reading this post

Warped Ambitions?

Just spotted this in the Guardian:

starship enterprizeNext Thursday, the British Interplanetary Society is bringing together physicists for a conference entitled Faster than Light: Breaking the Interstellar Distance Barrier. “The main purpose is to raise awareness of this obscure field of research within general relativity and quantum field theory and attract new and particularly young researchers to work on the technical problems,” said organiser Kelvin Long.

Wow! I had no idea there was such a meeting. Did anyone reading go?! What is the British Interplanetary Society? From their site I found this quote: [...] Click to continue reading this post

Lookin’ For Some Hot Stuff

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Hot, hot, hot, hot stuff
hot, hot, hot
hot, hot, hot, hot stuff
hot, hot, hot

- from “Hot Stuff”, by Donna Summer (1979). I refer to not only the physics but the c. 100 oF temperatures we’ve been having here every day recently.
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On my way back from the conference, I spotted this book (left) last Saturday in Foyles (the booksellers) in London 1. Quark Gluon Plasma book It is a collection of reprints of a lot of the papers forming the foundations of the physics of the quark-gluon plasma (QGP) idea, going back the early to mid 1970s with such papers as Collins and Perry (Gosh, I had no idea Malcolm was one of the early workers on this idea. He’s much more thought of as associated with black holes, gravity, strings and so forth, ideas which – ironically – have recently turned out to be relevant to the discussions of the physics too. See my recent post, and there are also various popular articles to be found2).

Putting aside the usual ridiculous price that Springer Elsevier charges for books, I found myself in two minds about this book, in view of the surprises being uncovered about the properties of this remarkable state of matter at the RHIC experiment. Is this collection of early papers a useful working tool, or is it now just of historical interest, since many of the basic expectations about the properties of the plasma seem now to be incorrect?

rhic collision of gold ionsWell, after a bit of thought, I decided that the latter view would be way too hasty. First and foremost, on a general level, even if some of the computations in some papers were done in the “wrong” light (it’s a strongly coupled liquid that flows, not a weakly coupled gas of quarks and gluons), much of their content will still be useful in many ways – good and correct calculations last for all time, it is the sense of the words decorating them that may crumble over time. More specifically, one can worry about whether there were assumptions (and approximations based on those) that went into the computations that will render [...] Click to continue reading this post

Exploring QCD in Cambridge

exploring qcd sign

So the conference here at the Newton Institute in Cambridge is simply marvellous. I’m so glad I came, and so happy that I was invited to attend and make a contribution to it by giving a talk and having discussions. It’s a rather splendid combination of experimentalists, phenomenologists, and various hardcore theorists of various sorts, and there are ideas just flying around and bouncing off the walls. The title is “Exploring QCD: Deconfinement, Extreme Environments and Holography”, (it’s organized by Nick Evans, Simon Hands, and Mike Teper) and the focus is very much the fascinating nuclear physics of heavy ion collisions at the RHIC experiment at Brookhaven, and the experiments to come on heavy ion collisions at the LHC at CERN. The latter is an aspect of the physics to be done at the LHC that you don’t hear about much because it is sidestepped in favour of discussions about the Higgs, origin of mass, supersymmetry, theories of everything – such as strings, microscopic black holes, extra dimensions and all that other good stuff. (See earlier discussions here, here and here.)

Well, the great thing is that there’s been plenty of discussion of black holes, extra dimensions, strings, and so forth at the conference because of a great deal of promise of its relevance to nuclear physics. It’s been right alongside the discussion of experimental results, and other theoretical approaches such as work on computer simulations of aspects of QCD (“lattice QCD”) and studies involving other techniques. There’s very much a spirit of open-minded exchange among all the various parties [...] Click to continue reading this post