Category Archives: research

Local Connections

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Well, Thursday’s meeting was a blast! I had decided not to try to get people to RSVP for the meeting this time, and so when it came down to the day before, I had no idea how many were going to show up. This meant that I had to make some guesses about how much coffee and tea and cookies to organize, which was a little bit of a challenge. But just before 9:00am people began to show up, and kept showing up, and by time I was ready to start off the day’s meeting, there was a really good crowd!

In the end it was a great day, with five really good talks and lots of excellent discussion. […] Click to continue reading this post →

Southern California Strings Seminar

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Southern California String Seminar May 2011 in progressThe next Southern California Strings Seminar is on Thursday 13th December! I’ve now made the website for this one and it is here. Come back to it from time to time to see the updates of talk titles as speakers let me know what they are. It is a one-day event filled with five talks and plenty of time for discussion. I’ve snagged a lovely room in the Doheny library again. (Photo left has a shot of the room we used last time it was at USC in May 2011. The most recent one was over at UCLA.)

You are welcome to come and do physics with us! Also, if you’re part of a group in […] Click to continue reading this post →

Talking

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…Again. I’ll be on the road again this morning. Heading to California State University Long Beach. They invited me to give a colloquium a while back and I agreed, and when I returned from New York last week I realized I needed to urgently spend a chunk of time thinking about what I was going to talk about, and designing a set of slides for it. The last couple of days saw me devoting a lot of time to it. Eventually I decided to dig back into ancient times (the 1990s) surveying some of the interesting things we’ve learned about strong coupling phenomena (involving unexpected reorganization of degrees of freedom and the number of spacetime dimensions at times), and then discuss what it all might be good for in view of work going on in the last decade or so.

Come to think of it just this moment, this is a chance to do a tribute to David Olive, who passed away earlier this month. (He was one of my professors when I was at Imperial College in the ’80s.) Ideas of strong/weak coupling dualities and their utility were given a huge boost by his work in this area from decades ago, perhaps the most famous being Montonen-Olive duality… I must remember to mention that in the talk. (See here for an archive of 2004 talks in celebration of his work. I borrowed the image to the right from there. I do not know who took it.)

Here’s the title and abstract: […] Click to continue reading this post →

The Future of Physics

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On Saturday we had another series of celebration events for the 50th Anniversary of the Aspen Center for Physics. It began at 2:00pm with a discussion in Paepke auditorium entitled “The Future of Physics”, and it was introduced by Michael Turner, and moderated by Lisa Randall, with three Nobel Prize winners forming the panel: David Gross, Bob Laughlin, and Adam Riess. (I decided to do a short sketch during some of it, and then quickly splashed on some colour later in the evening*. The result is above. The sketches are meant to give a sense of the stage and people on it, not be representative likenesses, so I refer you to pictures of them for actual portraits…)

There was an excellent turnout, and audience members were treated to a good and wide-ranging discussion. It was a difficult subject to grapple with, and Lisa started out in a good place, by getting each panelist to take turns to describe their way into physics, then around again to talk about the areas they got their Nobel Prizes in. She supplemented their contributions with some of her reflections on her own experiences and points of view, and tried to unpack some of the concepts brought up here and there when she thought it might help the audience.

From there, things became a bit tricky, since there were several directions in which to go and it was not clear what the best structure to follow was, given the time allotted and that they needed to stop and get members of the audience involved. Like I said, it was a difficult assignment for all of them. What emerged was a loosely structured series of interesting reflections from each of them at various points, some healthy disagreements there and here (I think it was good for the public to see that we’re not all cut of the same cloth) – for example between David and Lisa on the meaning of […] Click to continue reading this post →

Strings 2012 Talks

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I did not make it to the annual “Strings xxxx” conference this year (where xxxx = current year), but I heard that it was good. It was held in Munich. See the lovely poster on the right. (I wonder who did the splendid painting?)

The organizers did a great job of rapidly updating the website with slides and video of the talks so that a wider audience can benefit from them. The video page is […] Click to continue reading this post →

Working Group

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It wasn’t all lecture halls, discussion rooms, and cafeterias for the workshop. The organizers arranged for a boat tour last week, and we all sat on one of those splendid long, wide and low tour boats that you often see on the canals in Amsterdam. It was nicely equipped with a bottle of wine at each table, and the crew members handed us each a glass of sparkling wine as we embarked. Very nice. There was a lot of fun chatter from each table for the whole trip around the canals (so much so that they stopped the attempts to inform us over the PA system about some of the sights we were seeing, since the sound was drowned out by the conversations), covering (from what I could hear) a wide range of topics from well beyond physics to matters concerning topics presented in the workshop.

Sometimes pads of paper and pens appeared. Above is a group (David Tong, […] Click to continue reading this post →

The Bridge

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The workshop has been fantastic, overall. In between discussions, the talks, and some thinking about my own projects, I’ve had some time to wander a bit, and look around. Yesterday after lunch I wandered a bit and then found myself settling down and doing a sketch of a bridge at a junction with lots to see. The Amstel is joined by Prinsengracht canal here, and it was fun to sit a while and put down some pencil lines, followed by firmer ink lines. I pulled the result into the iPad and splashed on some colour for good measure.

Having finished the paper last week, it has been fun to field questions about it from various people, as well as think at a more leisurely pace about the next […] Click to continue reading this post →

Slow Writing

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Well, the workshop is going well. I had to miss a talk this morning in order to carry on with this writing of a paper I was doing. Basically, we’re over due in producing our submission to a special volume of some publication or other that is going to be all about magnetic fields and models of strongly coupled matter… As you may have gathered by now, I’ve dabbled in magnetic fields for some several years by now, so it was natural to be asked. My collaborator in a lot of these dabblings, Tameem Albash, and a student, Scott MacDonald, and I have been working on a suitable project for a while, and due to my travels and entanglements with a previous project, I’ve made us all a bit late.

The last few days have been difficult for writing. I’d forgotten […] Click to continue reading this post →

Happy Higgs Day?

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Dont forget that today there will be big announcements of the latest results from the LHC about the search for the Higgs…(and some of us are hoping for news about what might be the beginning of the search for what lies beyond…)

There are so many live blogs, so follow a few… Like Resonances… for an expert view, Matt Strassler, for another expert view, or Quantum Diaries, for a non-expert view.

Exciting!!

(update… Looks like it is a strong enough set of results, statistically, to call the Higgs discovered… Hurrah! And with possible hints of new physics too? Excellent….)

Further update… A CERN press release is to be found here. Also, looks like any deviation from the standard model Higgs, at least for the decay channels examined so far, is very small… So there’s a lot left to do and understand…

-cvj Click to continue reading this post →

Amsterdam!

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20120703-164422.jpgAmsterdam! I’m here for a workshop for a while. It is on string theory – many aspects – and so the mix of people is a good one overall, with conversations ranging from high energy physics, the LHC (including the Higgs announcement at CERN expected tomorrow) and black holes all the way over to condensed matter and various kinds of exotic physics one can do in the laboratory in that context. It should be an excellent time here… It is good to be back in the city after over a decade, and to catch up with a number of friends and colleagues in the field. I also want to properly explore the city this time, not having done that much exploration last time. (Photo above is a snap taken of the lovely moon that came out last night, with the Amstel and accompanying reflections and so forth… Was pretty to see.)

I’ve been trying to read some notes in preparation for working on a draft of a […] Click to continue reading this post →

Has the Fat Lady Sung?

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The OPERA experiment has reported that they may have found the source of the timing discrepancy that produced the result that neutrinos moved apparently faster than light. It seems that there was a faulty connection that affected the timing measurements. Here’s a physics world article on the matter, along with a link to a CERN press release. (Note that there are some doubts related more directly to the GPS timing signals they used, which on their own would make for even faster neutrinos, but clearly there’s cause to really doubt their strong claim from back in the Fall and take a step back.)

You’ll recall the huge press storm about it last Fall, accompanied by all the usual hysteria about the establishment (this time, Einstein) being overturned. I blogged about it here, with the noncommittal title “No, Uh-uh, Nope, Nuh-uh”. They’ll be doing more experiments later in the year, as will a number of other groups, in order to solidify the results one way or another. It’s clear that most people have decided the whole business is over, and will turn away from it to other things. Some will be pleased, some annoyed, some confused, and so forth.

My hope is (as I discussed in the article I wrote back then) that this gets as much […] Click to continue reading this post →

Scribbling about Quantum Gravity

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So I mentioned that I was doing some more material for the Nova people, via their website. (See here for some earlier material about Multiverses.) They’ve a blog called The Nature of Reality with contributions from many interesting people. Well, now they’re featuring those pencasts I think I told you about in an earlier post.

The pencasts are all about Quantum Gravity, a major research topic in physics. I talk about what it is and why we care about it. I speak and write, scribble and draw and […] Click to continue reading this post →

Tune In!

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Later today, there’ll be a joint seminar by physicists from ATLAS and CMS, the two experimental halls at the Large Hadron Collider (LHC) looking for evidence of the Higgs boson. This will be the first official announcement of the physics seen (or not seen) by the combined results from both independent searches. Neither search has enough data to announce a discovery of anything (as far as I’ve heard) and the combined results would not constitute one either, but people are hoping for at least some nice hints of something suggestive that support each other. We shall see! this is an exciting time, as you’ve read me say before, and so I recommend looking out for what will be announced. Even a negative result (e.g., “we’ve found nothing yet”) […] Click to continue reading this post →

Almost at an End

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I’ve had a fun time over the last few lectures with some more mature topics, pointing the students to things that they will see more (I hope) in the advanced class next semester. We covered the large N Gross-Neveu model in some detail, giving me the opportunity to give a glimpse of several important topics and techniques… at large N the 2 dimensional model’s solution is exact, and it shows important phenomena such as spontaneous chiral symmetry breaking, dynamical mass generation for the fermions and dimensional transmutation. These are all important phenomena shared by (the more difficult to study) quantum chromodynamics, the theory of the strong nuclear interactions. (See an earlier post about some of these properties and what they are… there’s also a mention of a new general level book that goes into some detail on the physics and the history.)

The other thing I took some time to explore was the diagrammatics of the model, and the interesting patterns that emerge […] Click to continue reading this post →

Infinity Coincidence

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So here’s an interesting sequence of events. On Tuesday in the QFT class I finished the lecture on Renormalization Group Flow, and the idea of a “beta function”, unpacking the results we’d accumulated from QED and quartic scalar field theory to use as illustration. The key result, for those of you about to scroll away (or the few of you who have not, but are hovering over the scroll bar), is as follows. Never mind what a beta function is right now. The issue at hand concerns whether it is positive or negative for a force of interaction being studied. A positive beta function tells you that the strength of the interaction between constituent things (particles, etc) gets weaker as you work at lower energies… This is an important result in understanding how Nature behaves in a variety of situations… one way of seeing variety is to look at different energy scales, and sometimes what seems familiar takes on different character. The converse is true… that positive beta function tells you that the interaction gets stronger at higher energies… Energy is also rather like the inverse of distance scale too, so high energy is akin to shorter distance scales (higher resolution), and low energy like longer distance scales (grainier resolution). In other words, looking at stuff in really tiny detail means using higher energy… and the nature of that stuff can change when you look at that sort of resolution since the way things interact changes… For electromagnetism, for example, we see that it gets stronger the closer we look, digging more deeply into the structure of the atom, say, probing the charged constituents of the nucleus once we’ve understood electrons. The result is that you see the electromagnetic interaction changes, ultimately turning into something else… (it merges with one of the nuclear forces, in fact…but that’s a story for another day)

So anyway one of the things I ended the class with was the idea that if you had a negative beta […] Click to continue reading this post →