I learned* that over on the Huffington Post, Christian Ott (Caltech) wrote a piece describing research on modelling stellar explosions using supercomputers. When a star goes supernova, what exactly happens? Capturing the physics that goes on is a very difficult problem to do, and in the article he explains some of the difficulties, and some of the recent progress.
There’s a slide show showing some of the […] Click to continue reading this post
This diagram is the cycle for another heat engine (using a black hole as the working substance) that I studied in the recent paper. It is a path made of two constant pressure legs (isobars) and two constant volume legs (isochores) that happen (due to the properties of static black holes) to also be adiabats. See the post.
It got included in the paper as another example where one could compactly write down something useful about the efficiency, since, as it turns out, you can write closed form expressions […] Click to continue reading this post
As a contrast to yesterday’s quick caricature effort, I went back to one of the pictures in the magazine and did a more careful pencil sketch. Very different kind of exercise and technique needed to coax out the things I wanted to bring forward. It is a scan of pencils, so beware that it is not as representative of what’s on the page in some ways. To add to that I really should do a lot more finish work on this one (rendering of shadows on […] Click to continue reading this post
This is a good one from the Onion. (I’ve not looked in on them for a while, so this was a funny thing to return to see…*) The title says it all: “Top Theoretical Physicists, R&B Singers Meet To Debate Meaning Of Forever”. Extract:
[…] at the four-day symposium, where they grappled with extant questions regarding the concept of forever that remained unresolved, such as whether forever is better conceived as an infinite, four-dimensional expanse of space-time or, rather, what one second feels like when you’re away from your girl.
“For many years, the R&B community has posited the classic notion that forever is presumed to go on and on like our love,” said Edward Witten, a string theorist at the Institute for Advanced Study, who acknowledged that while time appears to extend unendingly, it is paradoxically composed of discrete moments such as a tender embrace or a single perfect kiss. “This assertion then raises a problem of even greater […]
Lovely bit of sitting in the sun for a short while after breakfast this morning relaxing by doing some quick freehand sketches from pictures in a magazine. I was experimenting with a pen I love but don’t use much at all – One of those nice inky brush pens by Pentel. Gives some interesting lines that take some getting used to since it is quite a different mark-making tool than the pens I […] Click to continue reading this post
On Monday 28th April at 8 PM Eastern time (5 PM Pacific) I’ll take part in a live radio interview that you might want to listen to, on a show called Alpha Centauri and Beyond. I guess I’m in the “Beyond” bit? I don’t really know anything about the show except that they like to bring people on to discuss ideas, and when I get a call to come and help sprinkle a bit of science, you know I’m likely to say yes if I can spare the time.
You can see a link to the details here, and you can listen online. As you can see it is advertised as being about me explaining string theory. Well of course that billing is nothing to do with me – I can’t hope to explain any complicated subject like that in the time available – but if asked I will do my best to try and motivate some of the ideas behind the subject. I hope it will be a fun interview and that […] Click to continue reading this post
Yes, you heard me right. Holographic Heat Engines. I was thinking recently about black holes in universes with a cosmological constant and their thermodynamics. I had an idea, it led to another, then another, then some calculations, and then a couple of days of writing, calculating, and thinking… then a day to cool off and think about other things. Then I came back to it, decided it was still exciting as an idea and so tidied it all up as a paper, made some diagrams, tidied some more, and voila! A paper submitted to the arxiv.
I’m sort of pleased with all of it since it allowed me to combine a subject I think is really fun (although often so bleakly dull when presented at undergraduate level) – heat engines – with contemporary research ideas in quantum gravity and high energy physics. So I get to draw some of the cycles in the p-V plane (graph of pressure vs volume) representing the inner workings of engines of particular designs (just like you might have seen long ago in a physics class yourself) and compute their efficiency for doing mechanical work in exchange for some heat you supply. It is fundamental that you can’t 
do that with 100% efficiency otherwise you’d violate the second law of thermodynamics – that’s why all engines have to have some exhaust in the form of heat, giving an efficiency represented by a quantity [tex]\eta[/tex] that is less than one, where one is 100% efficient. The diagram on the left illustrates the key pieces all engines must have, no matter what working substance you’re using. The details of the design of the engine are what kind of cycle you taking it through and what the properties (“equation of state”) your working substance has. In the case of a car, for example, the working substance is cleverly mixed up with the source of heat – the air/gasoline mix forms a “working substance” that gets expanded and compressed in various ways (in the green bit of the diagram), but the fact that it also burns releasing heat means it is also the source of the heat that comes into the engine (the flow from the red bit) to be (in part) turned to work, and the remainder flowing out to the blue (exhaust). Very clever.
The cool thing here is that I’m using black holes as the working substance for […] Click to continue reading this post
Did you catch the eclipse last Monday? It was wonderful. Here’s a little snap I took of the progress (taken with an iPad camera precariously through the lens of a telescope, pointing out of a bedroom window, so not the best arrangement). One of the striking things about looking at the progress of it is just how extra three-dimensional the moon seems as the earth’s shadow slowly covers it. It really makes one’s whole mind and body latch on to the three dimensional reality of the sky – you really feel it, as opposed to just knowing it in your head. That’s sort of hard to explain – and you’re not going to see it in any photo anyone can show – so I imagine you are not really sure what I’m getting at if […] Click to continue reading this post
Eventually, although a bit over-priced in the Hollywood farmer’s market, I do fall for these at least once in the season. As someone whose job and pastimes involve seeing patterns everywhere, how can I not love the romanesco? It’s a fractal! There are structures that repeat themselves on different scales again and again, which is the root of the term “self-similar”. Fractals are wonderful structures in mathematics (that have self-similarity) that I urge you to find out more about if you don’t already know (just google and follow your nose). And […] Click to continue reading this post
Spotted in the hills while out walking. Three chairs left out to be taken, making for an enigmatic gathering at the end of a warm Los Angeles Spring day…
I love this city.
There is a total eclipse of the moon tonight! It is also at not too inconvenient a time (relatively speaking) if you’re on the West Coast. The eclipse begins at 10:58pm (Pacific) and gets to totality by 12:46am. This is good timing for me since I’d been meaning to set up the telescope and look at the moon recently anyway, and a full moon can be rather bright. Now there’ll be a natural filter in the way, indirectly – the earth!
There’s a special event up at the Griffith Observatory if you are interested in making a party out of it. It starts at 7:00pm and you can see more about the […] Click to continue reading this post
As you know I am a big fan of sketching, and tire easily of the remark people make that they “can’t draw” – an almost meaningless thing society trains most people to think and say, with the result that they miss out on a most wonderful part of life. Sketching is a wonderful way of slowing down and really looking at the world around you and recording your impressions. If you can write you certainly can draw. It is a learned skill, and the most important part of it is learning to look*. But anyway, I was pleased to see this nice way of getting people of all ages involved in sketching for fun at the book festival! So I reached in and grabbed a photo for you.
It is nice to see the variety of authors at a book fair event like this one, and it’s great to see people’s enthusiasm about meeting people who’ve written works they’ve spent a lot of time with. The long lines for signings are remarkable! As you might guess, I’m very much a supporter of the unsung authors doing good work in their own small way, not anywhere near the spotlight. An interesting booth caught my notice as I was wandering… The word “science” caught my eye. Seems that a mother and daughter team wrote a science book to engage children to become involved in science… Hurrah! So Jalen Langie (the daughter, amusingly wearing a lab coat) gets to be […] Click to continue reading this post
I looked for D-Branes, by Clifford V. Johnson… But somehow must have missed it…
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.)
A 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
