Moving on…


Hi everyone — I’ve still been getting a trickle of comments on this blog, which I find a little heart warming, but I wanted to let people know that this blog is now officially closed and there will be no further posts. My adventure in the UK ended in June and I’m now midway through my first year of a PhD in the US. (I’ll be back in the UK in April 2009 to attend the Beyond Part III conference and the SUSY breaking conference in Durham.)

For those who want to replace this blog with a more active RSS feed, might I humbly suggest the following physics-y blogs of similar flavo(u)r:

Take care, everyone!




A few thoughts on my adjustment back to the US…

“There are three things you can’t do in life. You can’tr beat the phone company, you can’t make a waiter see you until he’s ready to see you, and you can’t go home again.” -Bill Bryson, Notes from a Big Country.

  • I’ll never get tired of the dry, dry humo(u)r of passport control. “Cambridge? That’s in Massachusetts.” But believe me, it felt really, really good to hear the passport officer say, “Welcome home.”
  • One of the first things I had when I got back was Hot Dog on a Stick. Most of you have no idea what this is… it’s kind of a corn dog that’s sold at California shopping malls. Delicious and impossible to obtain in the UK.
  • I went to the Tudor House, a British tea shop(pe) in Santa Monica and discovered that the cost of a pack of [imported] McVitties digestives is the same as a gallon of gas.
  • It’s damn near impossible to find an electric kettle in the US. (I finally found one, but it was over priced and not nearly as nice as the £5 kettle I got at Woolies in Durham.)
  • I’m perfectly comfortable with the direction of traffic since two peripatetic years in the UK taught this Los Angelino how to get around without driving, but I’m still not used to the right-hand side being the passenger’s seat.
  • Other well-missed foods: fluffy pancakes with maple syrup, authentic American diner food, oreo cookies
  • I found myself with old lady syndrome… somewhat aimlessly walking the ailes of the supermarket marvelling at all of the new brands. I seriously spent ten minutes looking at all the chewing gum and candy at the checkout-line of my local supermarket. “Did they have sour altoids before I left? Man. What’ll they think of next?”
  • … and don’t even get me started about how much time I spent browsing through the cereal aisle.
  • I found that I didn’t really fit into the usual teenage hang-outs anymore. Two years living in the UK has like-oh-my-god made me like totally unable to like understand the way teenagers like talk to each other in this like country, y’know?
  • I desperately miss watching Doctor Who.
  • I met up with another Marshall Scholar in Santa Monica. He was passing through before returning to Cambridge and insisted that we have proper Mexican food. We were trying to figure out a local taqueria’s nontrivial system of queueing when one of the regulars helped us out. “Not from around these parts, are you guys?” she said, making typically American small talk (I missed small talk). Before I could say anything, my friend interjected, “No… we’re from England.” I couldn’t stop laughing as she suspeciously eyed him and his Cleveland accent.
  • My friends say that my accent hasn’t changed a bit (unsurprising), but I speak with a slightly different cadence and with a few different filler phrases. A bit odd, innit? (I don’t actually say `innit.’)
  • It took me a while to get used to LA smog and traffic again.
  • On another visit to the Tudor House, I saw Prof. Johnson (of USC, formerly of Durham) on his famous Brompton. I was unable to say `hi’ since he was in the bike lane waiting for a traffic light to turn green, but it made me very happy to see a local physics celebrity and Durham transplant. In fact, it was Prof. Johnson who first brought my attention to the Tudor House while I was still getting acclimated to Cambridge in ’06.

This is another post on my “farewell tour” (which will last until I can properly say farewell). I thought it was important to write one more literature guide since my QFT and SUSY guides seemed reasonably popular.

For the first time since the deep inelastic experiments of the ’60s the high energy physics community is approaching an energy frontier where we can expect the unexpected. The hep-ph community is shifting back to focusing on experiment-driven interpretation of collider data as we approach the era of the LHC.

This is all very exciting, but thirty years of top-down model building has left the community somewhat ill-prepared to teach its graduate students how to connect with experiments. Consider, for example, the large number of SUSY books/reviews out there versus the number collider physics books/reviews. It’s even harder to find reviews targeted to theory students rather than our experimental colleagues.

As a side project, I’ve started typing up a set of collider-physics-for-theorists notes for the local hep-ph group. Along the way, I’ve found a few nice sets of references that I think would be useful for any beginning graduate student with an eye on the LHC.


As a properly-trained theory student, you probably have more than enough technical background to navigate the literature. The main adjustment is learning to speak the same language as experimentalists. Before you start, however, you should make sure that you have a solid understanding of quantum field theory, in particular perturbative QCD. You should be familiar with the parton model and deep inelastic scattering at the level of Peskin’s book, though more basic books like Halzen and Martin might be enough to get caught up in a pinch.

Canonical Resources

  • Prof. Han’s Collider Physics Review (hep-ph/0507097, updated version here). This has been the main review for phenomenologists for some time now. It hits all the right topics and is at the right level for hep-ph students. Start here and fill in the details as you need them.
  • Prof. Wittich’s TASI08 lecture, “colliders for theorists.” Unfortunately, the TASI08 audiovisual link appears to be broken at the moment, so you might have to wait for the proceedings to come out.
  • Prof. Arkani-Hamed’s PiTP “LHC Crash Course.” An excellent talk (with excellent recording quality) on why we’re excited about the LHC. A similar talk with awful recording quality can be found at the KITP.
  • Green, High Pt Physics at Hadron Colliders. We’ve set up a local journal club for hep-ph students who want to learn about collider physics and are roughly following a similar strategy as Green’s text (do not confuse it with his experimentalist-oriented Physics of Particle Detectors text). This text was recommended to me by a string theory-trained postdoc at the ICTP who has been getting his hands dirty with collider physics. It integrates event generators into the text, which I think is very important since some computational saavy is required to really do work in collider physics. Green uses CompHEP, though our local journal club uses MadGraph.

Background Reading

For some undergraduate-level background reading, I suggest the relevant chapters in the usual particle physics texts. The latest edition of Perkin’s Introduction to High Energy Physics has a nice chapter on colliders. One might also look at Halzen and Martin or Martin and Shaw for basic references on QCD and kinematics.

You should review rapidity in special relativity. Collider physicists use a quantity called pseudorapidity (which is the rapidity in the massless limit) which you should be comfortable working with. Other kinematic quantities which experimentalists use are things like transverse momentum/energy/mass. It’s worth spending an afternoon working through all of the definitions and learning how to play with these quantities.

Stepping it up to more technical presentations, I recommend the following textbooks:

  • Barger and Phillips, Collider Physics. It’s not immediately obvious that this book is useful since it doesn’t really have the flavor of a text that you can just read cover-to-cover with well-defined goals in each chapter. Rather the book is more helpful as a reference when considering particular processes. I found their presentation of W\rightarrow e\nu and deep inelastic scattering very nice, though you should be prepared to fill in a lot of the calculations as exercises throughout the text.
  • Ellis, Stirling, Webber, Collider QCD. This book is close to my heart since it was written by Englishmen from CERN, Durham, an Cambridge (though Stirling recently moved to Cambridge). It is a text for getting your hands dirty with QCD at hadron colliders—perhaps a little bit overkill for theorists who lean towards Beyond the Standard Model-building, but it’s a fantastic resource.
  • Leo, Techniques for Nuclear and Particle Physics Experiments. This is my preferred reference for experimental nitty-gritty when it’s necessary. For example, how do calorimeters work and why do muons pass right through them even though at high energies they’re practically indistinguishable from electrons?


These are important, you’ll want to have these handy.

  • Particle Data Book. More important than the actual data on particles are the reviews on collider physics.

You’ll also want to have useful information at your fingertips about the detectors on the main stage. The best way to do this is to have the detector’s technical design reports on your hard drive. (Wikipedia works in a pinch as well.)

Additionally, the Journal of Instrumentation has a comprehensive “all you would care to know about the LHC” issue

Continue reading ‘Collider Physics for Theory Students’

Soon I’ll be off the blogosphere. Will I be back? (A question relevant to all of maybe two or three people.) I have mixed feelings about whether it is wise for a PhD student to moonlight as a blogger.

On the one hand, it’s a great way to connect with the physics community. The way that physics bloggers have been able to share news, advice, and commentary has already changed—in a largely positive way—how this generation of physicists approach their craft. On a personal level, blogging has been a tool to help me codify my thoughts. Many of my physics-related posts were exercises in how to present topics effectively and later made their way into my presentations and write-ups. Once in a while someone will comment on something they think is neat, and that always makes me happy.

On the other hand, a prominent blogger once offered the advice that it’s dangerous to blog without tenure. There is a caricatured image of grad students as working 200% of the time. While this is clearly not true in practice, it still doesn’t look great when you hit a ‘rough patch’ in your research but you still manages to make regular blog posts. Further, no matter how many insightful posts you write, you’re always a single bone-headed statement away from offending someone senior with a lot of power over your future. (So when the grown-ups are having blogo-wars with one another, Junior would be wise enough to stay out of it.) [I will note, however, that I’ve heard a few people say that blogging has *helped* their early careers.]

I haven’t complete closed the door to future blogging. Maybe somewhere down the line I’d be interested in joining a group blog of young scientists, but this very-hypothetical situation wouldn’t happen in the near future and would only occur after a long talk with my adviser.

Thank you, however, to all of the kind comments people have left regarding keeping up blogging. I strongly encourage everyone—especially all of my grad student colleagues—to maintian Sidney Coleman’s “fratelli fisici.” A big part of being a physicist is collaboration. We are privileged to live in a time when this can occur at a much earlier stage through resource and information sharing over media such as web forums, wikis, and blogs. So keep an eye on the big picture and look out for each other.

This unfinished draft has been sitting in my blog directory for almost two years now. I think I’ll just leave it as-is and share it as a memory of my first week in the UK. I have similar scraps of paper recounting thoughts while I was on the plane to London, on the train from Cambridge/to Durham, and on the plane home.

After a weeklong whirlwind of an orientation for the Marshall Scholarship, I’ve finally plugged in my ethernet cable into a cozy dormitory in Burrel’s Field of Trinity College, Cambridge University. If you don’t understand what ‘Trinity College’ means relative to Cambridge University, don’t worry, I’ll explain that in a later blog post along with my reflections on the Marshall orientation.

In the meanwhile, at the expense of writting about the past week’s events out of order, I’d like to reflect on my arrival in the UK’s second oldest university.

To set the stage: It is raining in London.

Imagine feeling a little sad, a little anxious, and a little wet. You’re sad because you just spent a week with 44 of the most amazing people you’ve met and now it’s time to go your separate ways. You’re anxious because you’re heading to a new school, a new home, and a new country (presently dismissing London as an international city). You’re wet because… well… it’s raining in London.

Epilogue: I left the above text completely unchanged since I first wrote it in 2006. I have other bits of paper with hand-written thoughts of Durham, the UK, etc… but these are unfortunately tucked away in a scrapbook in LA. On the day that I left Cambridge, however, I remember writing about how the city looked as I took the cab to the train station. It had rained the night before, but the sky was clear. The morning light reflected off of the grass and the colleges have never looked as stately as when they are enveloped in a bit of mist and dew. This is how I will always remember Cambridge: sparkling.

Here are a few totally random snippits that I had hoped to incorporate in some posts. Enjoy!

  • Anybody who has not already done so should play with arXiv Structure. It’s not perfect, but it does a very good job of creating a ‘web’ of interconnections between papers. It’s a great tool for skimming the literature for a given topic and finding review articles.”
  • There’s been a lot of blogosphere buzz about people’s “bets” for new physics at the LHC. All of these bets usually involve some nominal sum of money and are made by people more knowledgeable than me and most of my grad student colleagues. As beyond-the-Standard Model grad students, however, our choice of projects constitutes a sort of bet about what direction the LHC will take our field. Instead of money, however, we’re wagering our academic futures.
  • New math songs. I recently found Tom Lehrer’s song making fun of the 1960s New Math movement. I was completely in stitches, however, after I found Bo Burnham’s much more risque `New Math’ song. (I had to listen to it a few times to catch everything.) Unlike other Math songs, (e.g. The Klein Four Group), Burnham’s song is not politically correct by any stretch of the imagination, but it certainly had its clever moments.
  • For something a little more physics-based, I recently bought a copy of Peter Dong’s Les Phys CD of his Harvard undergraduate Math/Physics honors thesis. A sample song can be found on Professor Georgi’s webpage. (Unfortunately the lyrics to the other songs on the CD are a bit more difficult to hear.) For those who are interested, the CD can be purchased form Jeff Moran’s site.
  • Californians (especially those from San Francisco or LA) like to think of themselves as very worldly people. This is true in the sense of having diverse backgrounds, though most Californians my age thoroughly speak and think in much the same way despite looking very different from each other. At Cambridge, however, it was refreshing to have friends from all over Europe with their own national cultures and perspectives. In Durham, the group of postgraduate students included a much wider range of students from across the European and Asian continents. The ICTP, however, was a thoroughly refreshing experience full of a cacophony of languages and researchers from all over the world.
  • The Marshall Scholar Farewell dinner in London (last May) drove home one piece of advice that has characterized my Marshall experience: surround yourself with amazing people. It will inspire and motivate you in ways that you cannot before-hand imagine. This certainly holds true of all of my Marshall, Cambridge, and Durham colleagues and friends — I sincerely and deepy thank all of them for sharing their passion and vivacity.
  • In a stroke of unexpected synchronity, I was able to meet up in New York City with a group theoretical physics friends from my undergrad years in Stanford and, simultaneously, theoretical physics friends from my Part III year in Cambridge. This was a really, really special event since we are all theorists (from hep-ph, hep-th, astro-ph… unfortunately Steffen couldn’t make it, so no gr-qc) of the same year. The concentration of talent in our group was very impressive — I wish I could have taken a group photo before we all went our separate ways. Another thing that my years abroad have taught me is that a large part of doing physics is maintaining a network of friends and collaborators, and I really hope that our group will stay close as we inevitably bump into each other several times in our academic careers.
  • England seems to have a growing problem with knife violence and “ASBO” thugs beating up people. Urban cities in the US have much less of a problem with this for what appears to be the plain fact that guns are legal. Don’t misinterpret me: gun violence is a big problem in the US and I’m not condoning guns at all. I will offer, however, that the underlying problem in both places appears to not only be the implements of violence, but the culture of violence itself.
  • Even though a place can initially seem very different or even uncomfortable, people have a tremendous ability to not only adapt, but to enjoy it. I wonder, however, how much my experience was colored by my knowledge that it was temporary. I knew that I had a PhD position back in the US and could afford to take the attitude of “holding my breath till I get home” if I ever felt homesick.
  • I’m not an adventurer travelling to a distant foreign land. Britain is about the most US-friendly place one can go outside of North America.
  • If you want to make new friends, be bold and leave the comfort zone of your old friends once in a while. Some of my best friends in Durham were non-physicists whom I got to know because I was hanging out in the graduate bar.
  • For everyone back in the UK: America is very different from you see on TV. I guess the same holds true for Americans’ preconceptions of the UK.
  • One of the most useful conversations you can have with your adviser starts with this line: “How am I doing [as a student]?” Such conversations naturally come up when you’re asking for letters of recommendation, but by then it’s usually too late to modify your behavior. As a PhD student, I hope to be able to have a frank talk with my adviser at least once a year to check up on what my weaknesses are and how I should work on them, how I should fine-tune my approach to my work, etc. This is why you have an adviser, make sure to have these conversations.
  • A sign that I must be doing something worthwhile on this blog: I found a nice article about the proposed SLAC name change in the San Jose Mercury News. It seems to have borrowed quite a bit from a post that I made previously. I contacted the journalist and she said that she couldn’t find a way to reach me… and so she just completely copied part of my blog post and used it without attributing this site. And to top it all off her article referred to me as a “wag.”

Race and ethnicity in the UK is something that I really wanted to write a proper blog post on. Unfortunately, at the end of the day, my experience was just too limited for me to say anything really meaningful.

From the perspective of a Los Angelino, one of the most fascinating (and at times jarring) aspects of UK culture is the interplace of race and society. I am not qualified to make broad statements about the UK, but my very limited experience shed some light on how people in the UK “see” and “interpret” race and ethnicity. Such perceptions are inevitably tied up to class and privilege, for example, I’ll never forget an anecdote by former Trinity Master Amartya Sen where the Nobel laureate was stopped at Heathrow because he listed the Trinity Master’s Lodge as his residence on his UK entry form. Passport control looked at him and incredulously asked, “does the Master know that you’ll be staying with him?”

In Durham I would randomly find people complimenting me on how well I spoke English. Newspapers across Europe are full of editorials about how countries ought to `deal’ with poor, minority immigrants. Less-proper English school-children will ridicule one another with racially-charged language that would be well out-of-bounds for even the most knavish of their American counterparts. Minorities in Europe seem more likely to form ethnic enclaves than American minorities. Alternately, minorities in Europe hold on to a stronger sense of heritage even after the first generation of immigrants. I get the impression that American minorities are faced with less an “either-or” decision between mainstream American culture and their ethnic heritage. Mixed-race marriages seem to be a bit less common in the UK; though I have not looked at the census data.

At the same time, British television seems much more comfortable incorporating `real’ (i.e. non-“token”) minorities into its programming. In this sense I have much more confidence in the UK’s youth to make great progress in approaching a society that can simultaneously embrace the richness different cultures while maintaining a national identity that is inclusive of all its members.

At the end of the day I’m not sure how to really piece together my experiences in the UK in terms of a coherent message about race. They were certainly colo(u)red by my own vantage as an ethnic `minority,’ as an American (where race is a much more overtly sensitive issue), and as a student. One’s experience in a Durham college will vary greatly from a local Durham pub, or a Cambridge college, or a London pub, etc. etc. etc. I would love to hear from other American ex-pats on their thoughts on this topic.

LaTeX Etiquette


Here’s another post that I wished I could flesh out more had time permitted.

A few subtler points of LaTeX etiquette…

  • Quotation marks: use ` and “ instead of ‘ and ” for opening quotations, or else your quotes will look silly.
  • Bras and kets: use \langle, \rangle instead of less-than, greater-than
  • Align your equations! It’s a pain to read a calculation when the equal signs don’t line up. Advanced: if you want to be really proper, use “align” rather than “eqnarray.”
  • Use “\phantom” letters for spacing the indices of giant tensors.
  • Be careful with spaces.  For example, be consistent about how you space your reference numbers: “blah blah[13] .” vs “blah blah [13].” vs “blah blah [13] .”
  • Be careful with capitalization. Do you write “Figure 13” or “figure 13”? Do you write “Equation 7” or “equation 7” or “equation (7)”? Be be consistent.
  • Nothing says “I stole this image off of someone’s conference slides” like a pixellated image. This seems to affect Windows users more since the resolution of an image copied by Adobe Acrobat depends on how zoomed in one is to the pdf. (In Mac a copy-paste of a pdf usually preserves the native resolution.) If you really must, steal the original image from a paper by downloading the paper’s source from the arXiv. Always ask for permission from the authors.
  • Use the “hyperref” package to produce hyperlink-friendly PDFs. This is actually a really, really big help since some PDF viewers like Skim will allow mouse-over previews of an in-document reference. Thus instead of having to go back and forth with the scroll bar whenever I want to look up your references, I can juse put my pointever over “Reference [13]” to get a mini-window that shows the relevant section of your bibliography.

This is an old post that I never got around to fleshing out and finishing. I figured it was worth posting before letting my blog freeze-out (yeah, that was a Boltzmann equation reference).

More than half a decade ago I was sitting in the same course and had a very inspirational TA and now I’ve been toying with the idea of TA’ing the “honors” freshman physics sequence at my new university.

Along those lines, I’ve been thinking about a few ideas that I don’t think are emphasized enough in the typical undergraduate curriculum. These ideas, I think, are important in developing a healthy ‘physics intuition.’

  1. Symmetry. The use of symmetry to solve problems, group theory as the language of symmetry. E.g. how to we `intuitively’ use symmetry to reduce higher-dimensional problems to lower-dimensional problems (e.g. polar/spherical coordinates). Mention symmetry as a `deep physical principle’ in gauge theories, for example.
  2. Geometry. Emphasize the geometric foundation of physics, even in elementary physics. E.g. thinking of cross products as areas with an application to Kepler’s laws and angular momentum. This is a recurring theme that I think needs to be made explicit much more at every level. Lagrangian mechanics courses ought to draw more on the structures of differential geometry.
  3. Dimensional Analysis. Every freshman should understand the power of dimensional analysis and scaling. (I believe there’s a very nice textbook by Barenblatt.) More advanced students should see how dimensional analysis is still a very powerful tool, e.g. Stevenson’s excellent “Dimensional Analysis in Field Theory” review (
  4. “Duality”. E.g. Electromagnetic duality. More loosely, being able to interpret one problem in terms of another problem. e.g. hydrodynamics as E&M.
  5. Back of the Envelope. Learning to make good order of magnitude calculations.

Yeah, I’m supposed to have written my “goodbye” post by now… but things have been really busy. So instead, here’s a link to the PiTP 2008 lectures (recently released):