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Peter Steinberg | USLHC | USA

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Dimensions of String Theory

Wednesday, November 21st, 2007

Just as a follow up to my post on the string theory & RHIC workshop Columbia, the cover article of this week’s Science News is about the “duality” between gravity and gauge theories which has turned out to be one of the hottest topics for RHIC physics. The idea is that theorists can use gravity models to do things with strongly-coupled systems of quarks and gluons that they thought would require heroicially complicated quantum field theory calculations. One particular calculation from 2001 found that there is a lower bound on the viscosity of a strongly interacting system, and RHIC physicists have been putting enormous efforts into proving or disproving the bound in a real physical system. That this could be the first application of string theory in the real world has made both experimentalists and theorists excited, and given a lot of focus to the LHC heavy ion program (of which I am a part — an embattled part, but a part nonetheless!)

In any case, this is a nice human-readable article summarizing the state of the field, with only a factual errors that I noticed on first glance. Have a look!


Michael Schmidt 1954-2007

Tuesday, November 20th, 2007

This has been percolating around the community the last few days, but some sad news just came in via the ATLAS Secretariat:

Dear Colleagues,

We are saddened by the passing of Prof. Michael P. Schmidt, 53 years old, from Yale University who worked on the ATLAS TRT since 2003. He brought the Yale group into ATLAS with Colin Gay who is now at U British Columbia. The Yale group took on successfully a very critical item with the design, layout and prototyping of the TRT Read Out Drivers. Michael authored and co-authored numerous papers in physics and his advice was sought for many critical national committees. He was a Fellow of the American Physical Society and was honoured by his colleagues at a reception at Yale on Oct. 18, 2007. He is survived by his children Daniel and Julia, and by his parents.

We send our sympathy to all his family and friends.

Michael Tuts and Howard Gordon, U.S. ATLAS
Michael Zeller, Yale University
Fido Dittus, ATLAS TRT Project Leader
Peter Jenni, ATLAS Collaboration Spokesperson

A memorial page can be found online.

I took Michael Schmidt’s first-year course as a somewhat-unprepared Yale sophomore. Of course, the first few months were pretty tough for me, as I had not yet gotten used to the physicist’s way of seeing the world. Luckily for me, he was always straightforward and clear — and generous with his time to go over exams etc. But most important, he conveyed to me a real sense of the physicist’s lifestyle, e.g. when he explained why he was missing various lectures, to jet off to conferences or labs — which I found very exciting. Thus, my interaction with him was a non-trivial part of my eventual decision to become a physicist. So while I never interacted with him much after that, his too-early passing has a particular poignancy for me.


Branes Has A Flavor?

Sunday, October 28th, 2007

Naturally, many people are interested in the LHC physics program because of its promise to give a glimpse into whole new realms of physics: SUSY, extra dimensions, etc. A much smaller group is excited about the prospects of testing string theory in a completely different regime, via the proposed (and theoretically well-explored) duality between gauge theories and gravity. Leonard Susskind (everyone calls him Lenny, but I haven’t earned my stripes yet) has even been so bold as to call the physics which drives collisions at RHIC quantum gravity that is “blown up and slowed down by a factor of 10^20“. Lisa Randall was quoted in Seed last February saying that after her excitement about the LHC coming online in 2007 (ah, memories), exciting thing #2 was RHIC physics:

Also of interest is the recent application of string theory to the physics being done at the Relativistic Heavy Ion Collider (RHIC), where string theory permits some calculations that would otherwise be intractable. The idea at RHIC is to better understand the strong force that binds together the elements of a nucleon, and 2007 may see the theoretical advances of string theory inform the experimental results from RHIC.

From that perspective, it’s always boggled my mind why everyone hasn’t just dropped everything to understand both RHIC physics and string theory from this perspective. If the analogy really holds, then everyone wins: 1) heavy ion physics finally has a theoretical framework which is in principle better applicable than perturbative QCD (pQCD), which is only thought to work for asymptotically large momentum transfers between quarks and gluons (e.g. jets), and 2) string theory (although not necessarily a full “theory of everything” version) finally gets an experimental playground to propose and test observables. Even better, anything discussed at RHIC will have an immediate chance to be tested at 30x the energy at the LHC. People usually have to wait a generation for this kind of thing!

But reality is what it is and two factors work against this (what I thought would be inevitable) revolution. One, RHIC physics is still in its relative infancy and there is still lots of interesting debate about the meaning of various observables (although we all seem to agree that the “perfect fluid” we observe is deeply connected to the quark gluon plasma), and two, no-one is sure how to make a precise correspondence between the QCD we know, love, and use in real life, and the gravity dual that many thing should exist.

To catch up on things, members of both camps met up on Friday in one of the big lecture halls at Pupin Hall at Columbia University for what was called “AdS Strings Intersect with Nuclear Beams at Columbia“. It was unsurprisingly well attended by about 50 physicists, most from the NY-area institutions (Columbia, BNL, Stony Brook, Princeton, Yale) but a few from farther afield (e.g. MIT). The topics ranged widely, from overviews of the RHIC and LHC experimental programs (by Bill Zajc and John Harris), a discussion of QCD energy loss from a string theory perspective (by Steve Gubser, working from the blackboard and handwritten notes), applications of string theory to energy loss phenomenology (Will Horowitz, Hong Liu, and Derek Teaney) and an interesting discussion of bulk viscosity in QCD, which controls the transition to scale invariance (conformal symmetry) by Dima Kharzeev of BNL. A marathon afternoon to be sure, and not without its share of excitement and frustration, but everyone I chatted with agreed that the cross-currents between the nuclear physics at RHIC and the LHC and the string theory communities can only be a good thing, pushing both sides in directions they never expected.

Afterwards, about 20 of us ventured via NYC subway to a Turkish place in midtown for a post-workshop dinner. Good fun to let people finally hang out and discuss the open issues of the day (which had multiplied since that morning…you know what they say about the more you know…). We all certainly appreciated the Columbia Physics Department’s hospitality and Will Horowitz’ tireless work to pull the day together.

And, yes, the photos are up on my Flickr page. And as a bonus, I tried to write down a few of the good lines from the day:

  1. On the choice of r vs z for the 5th dimension (which are, duh, inversely proportional to each other making the “real” world sit near zero in one variable, and infinity in the other), Hong Liu suggested “always ask”
  2. “Wherever there’s tickling, there’s dragging” – Derek
  3. And while it’s not a “line” per se, the idea of branes carrying a “flavor” (i.e. using them to implement SU(N) symmetries) put me in mind of Return of the Living Dead and Halloween.

OK, so not that funny out of context, but it was that kind of afternoon.


Weddings and Proposals

Wednesday, October 24th, 2007

And boom — I’m back. I’ve been telling myself not to use this excuse for my disappearance (not just from this blog, but from everything), but just this One Last Time: since I last wrote, I’ve gotten married, gone on honeymoon, and returned. And while no stranger to jet lag, this last round was a doozy, and I’m only crawling out of it now. Still, no complaints here: both wedding and honeymoon were spectacular and I can’t begin to express how great people have been about giving me the space and time to do both.

That said, my future at the LHC beckons. So while I’ve managed to make good on one proposal (to my wife Kate), another is already in the pipeline. Those of you who read biographies carefully may have noticed that I never quite say that I’m part of the ATLAS collaboration. In fact, while I have been going to CERN fairly regularly for the last three years, have given ATLAS talks at major international conferences, and feel fully invested in the experiment and collaboration, it’s still not a fully fledged marriage yet (although with 1500+ collaborators, maybe I should drop this marriage analogy now…). While all signs have been quite encouraging, the Department of Energy has not fully committed to supporting all three big LHC experiments for Heavy Ion research. Thus, my bio lists that I am current working on a “proposal” to do this work at the LHC, and this is the thing taking up most of my energy and time in the last few months, and will do so for the next few. More on this later: just wanted to pipe up after my few weeks of silence!


36 Hours in Geneva

Saturday, September 15th, 2007

Oh, now the Grey Lady tells us what we should be doing in Geneva — and how long we should stay there? 36 hours? That’s a day and a half (3/2). Unfortunately, someone seems to have titled the web page “16hours.html” — or two thirds of a day (2/3). I’m detecting some mixed messages, or maybe just a typo.

Many of those who have spent essentially any time at CERN will have covered most of the writer’s suggestions. I visited LEP when I was a prospective grad student, and most of these things (Jardin Anglaise, Paquis, Les Armures, St. Pierre) were on the itinerary. Geneva has never felt like a fast-changing city. But then again, I missed the, um, Platinum Glam Club. So maybe I’m less surprised they don’t mention CERN anywhere in the article. Too bad — maybe I’m biased but I can’t recall a single visitor who wasn’t impressed, if not somewhat moved, by a visit to the lab.

That said, that I didn’t find Geneva to be a particularly stimulating place to be when I was there as a student in the 90’s. Lack of sufficient funds notwithstanding(the 25 CHF drinks aren’t that new of a phenomenon), the austerity of the Genevois was quite daunting to me, and I ultimately found myself really living in the French countryside, moving between various friends’ houses and the famous “farms”. Since then, sounds like the Genevois have moved to the country, and now some colleagues are choosing to settle in for the LHC era in town. Not too shocking, since I can barely keep up now with the new bars/restaurants/etc. popping up and disappearing all over the city. So times change, even if the Times may not be catching up so fast.



Friday, September 14th, 2007

I really intended to get another post up yesterday, and it might have been a good one: there are a few isolated musings on the LHC schedule by some anonymous bloggers out there. But I held my fire.

It’s so tempting when writing for a blog to start really keeping up with and responding to the blogosphere. I mean, it will be great to get all meta on everyone and even discuss Chad Orzel’s recent post about this website (and not just because he was/wasn’t complimenting me on my “veteran” status in the physiblogosphere…) But I checked with my more senior colleagues who couldn’t verify the rumors, and after a lot of soul searching, I’ve come up with a new principle: no gossip from unverified or anonymous sources. As much as I feel that “gossip” in general is actually good for science in general, reminding people that the decisions that are made, even about huge projects like the LHC and its experiments, are made by people interacting with other people, it doesn’t make sense to me at this point to let every quiver of good or bad news propagate outward under its own power, a la light in vacuum. There’s a lot of great journalism out there, fact checked, vetted, edited, etc. And there are lots of great physics blogs out there from different subfields with real named individuals on them who can take responsibility for the information they disseminate. While it would be fun to inspire debate, I think I’ll be conservative for the moment.

Am I wrong? I know I’m setting myself up to violate my own rules, but you have to start somewhere!  The LHC is getting to be such a big deal, both in its importance to science as well as its sheer bulk in terms of resources and mindshare, that the gossip is inevitable.  So maybe this is a warning to readers to take what they hear “around” with a grain of salt.  Fortunately, CERN hasn’t seemed to shy away from bad news when unavoidable.  Here’s hoping there’s not much to report until the spring!

(And super interesting that the Greek god of gossip is “Pheme”, the root of the word “fame”…)


The Divided Self & The Examined Life: LHC Style

Tuesday, September 11th, 2007

I mean, life’s tough enough when three experiments have a piece of you, but now I’ve committed myself to two physics blogs (that’s the “divided self” part — and William James looking at you from the right). As I did when I started working on Quantum Diaries (now defunct, but oddly still present — I just had dinner with Caolionn yesterday out here at BNL), I have tried to come up with a few rules:

  • Anything to do with ATLAS, US-ATLAS (the US component of the ATLAS experiment, for those arriving directly), CERN, trips to CERN, Europe, trips to Europe, and why the heavy ion program at the LHC will be an excellent complement to the continuing program at RHIC, will go here.
  • Everything else (New York, culture, amusing, frightening, quasi-personal, etc.) will land in my normal blog Entropy Bound.

That said, as life continues to speed up (all this and I’m getting married in 3 weeks), the conservation rules I discovered for myself years ago continue to hold. The obvious one is based on the Principle of Finite Time:

Life + Blogging = Const.

    Then again, the quality and quantity of well-remembered, fully-internalized time increases proportionally to the quantity and quality of blogging (no functional form, yet, though, although I do have Socrates glaring at you from the left, EXAMININ UR LIFE). So I have competing incentives. So it goes.

    Anyway, this should be an exciting year leading up to the May 2008 startup of the LHC. My personal angle will be slightly different than the others, with physics interests anchored in nuclear physics and the understanding of the quark-gluon plasma, pioneered by the RHIC program at BNL. So there’s a lot of LHC physics to ponder, even beyond the exciting discussions of the Higgs, Supersymmetry and extra dimensions. Heck, some of us have been wondering about how extra dimensions apply to existing experimental data for a few years now! How lucky we are to have a huge jump in energy to keep testing these ideas on even more data.
    In any case, glad to have you with us.