Monday, April 30, 2007

Response to the Response (Smolin vs. Polchinski)

Wow, I'm on fire today: 4 posts. Maybe it's that May 1 deadline, but maybe it's because there's just a lot of fun debate about physics going on, and a lot of it references the physics I do and love. Case in point: Lee Smolin has posted a reply to Joe Polchinski's online (Cosmic Variance guest blog) review of Smolin's The Trouble With Physics (something which I always meant to review online, but somehow lost my way...). I have no idea how I would have found this, except for randomly bumping into it on Peter Woit's webpage.

Anyway, I feel no particular authority to comment on most of Smolin's comments on Polchinski's comments, but just wanted to point out Smolin's comments on the applicability to heavy ion physics:
With regard to heavy ion physics, yes the applications of the AdS/CFT duality to this are interesting and important. But they should not be exaggerated. Polchinski does so when he says, “And so the quantum gravity that is manifesting itself in dual form at Brookhaven is likely to be the same one that operates everywhere else in the universe.” First because there is no quantum gravity here, in this particular application only the correspondence with classical supergravity arises. Second, what is the basis for the “likely” here? I can imagine an aether theorist making the same argument: aether theory must be right because after a lot of work the principle of relativity of inertial frames was shown to be a consequence of the dynamics of the aether, therefore since nature “uses a small number of principles in diverse ways”, the aether must be the right explanation for why this principle is observed in nature. Further, it remains the case that the calculations behind these claims are done with an extended super-symmetric theory, when real QCD has no super-symmetries at all. It may be that they get some things approximately right for reasons that have nothing to do with string theory, such as the use of a scale invariant theory to provide a rough approximation of a non-scale invariant theory, in an experimental regime which has approximate scaling.
I might want to comment that for any approach to "get something approximately right", if it's "merely" scale invariance, this is somewhat of a cause for celebration in heavy ions, considering the non-perturbative regime we seem to have found ourselves. Even if string theory was a mere excuse to get to the "right" ingredients for a useful theory, then it's worth the (continually fascinating) endeavors of the string community.

That said, even I have been somewhat confused about the "ontological" status of AdS/CFT as it related to RHIC physics. I asked Polchinski about this in early 2004 (when he spoke at Quark Matter 2004 in Oakland, CA), trying to see if the applicability of AdS/CFT meant that string theory was somehow "in" the physics we do at RHIC, unification and all. I remember him having no particular difficulty in saying yes to this, as reflected in the sentence Smolin quotes. Would that it were true, but I'm still more comfortable saying that it's a "mathematical" connection between RHIC physics and black holes, leaving the more subtle (i.e. physical) connections for the experts!

LHC Update: No Test Run

What a disaster. I missed this Scientific American piece last Thursday about "Magnet Trouble Likely to Complicate Start of Large Hadron Collider". The disaster isn't missing the article, but what it means for the machine, people, detectors, and even some physics. Naturally, any and every delay creates logistical issues for the machine installation, which is already enormously complicated even when things stick to the plan. But it's also somewhat tricky for all of the people who have already started trying to plan their lives around the potential machine schedules, i.e. when they and their postdocs and students should be at CERN. The detectors will suffer a bit since they won't get to take "test" data while the machine is ramping up. But finally, the physics community will be missing a chance to improve the "energy scan" of collider data. The original test run was supposed to be at "injection energy" (900 GeV), without any acceleration in the LHC itself. While there exists a huge volume of useful collider data from UA1/2/etc on particle multiplicities, spectra, jets, etc, this is all around 20 years old by now. Many measurements at RHIC and the Tevatron have already pointed towards wanting to measure these things much more precisely and in greater experimental detail.

I know this was a major reason for me wanting to get to the LHC early, so I admit that I'm pretty disappointed, but life goes on...

Robot Wars, Geneva - Solved

I blogged about this a bit over a year ago, somewhat baffled by the appearance of this videogame-inspired mosaic above a street sign in downtown geneva. Now today K pointed me to this post on about "space invader in D.U.M.B.O. area", which links to a Paris-based art site that has this interactive map of Geneva. Apparently the invasion has already taken place, and evidence is all over the city. Now I know what I should be doing next time I have a free afternoon on a sunny day during my next trip to CERN...

Light Through a Lens

For those colleagues of mine who don't keep up with the science blogs, even one as enjoyable as Backreaction, be sure to check out Sabine's recent guest blogger in her "Inspirations" series: former spokesman of the PHENIX experiment at RHIC, Bill Zajc. Bill is one of heavy ion physics' more eloquent spokespeople in general (e.g. see the story on RHIC physics he co-wrote for Scientific American last spring), and this latest example is no exception. And only one typo -- pretty good for a long blog piece (sorry, Bill!).

(shameless self-promotion of the day #1: Pertaining to this post, I did a piece for this way back in February.)

(shameless self-promotion #2: I'm going to be getting some official sponsorship starting tomorrow, when I'll be blogging as part of BNL's 60th aniverssary. Nice to have some pressure once in a while!)

UPDATE: Brant suggested I mention Bill's Wikipedia entry, for no other reason than the fact that he has one.

Friday, April 27, 2007

Fact-check of the week: Friedman vs. Einstein vs. Friedman

Nice to see a meditation on Einstein and intellectual freedom discussed in Friedman's op-ed today (OK, so it's Walter Isaacson's meditation -- couldn't a few more non-cliched Einstein quotes have made it in there?) but the Gray Lady's top man and editorial staff has let down its man it seems:

Tom Friedman says:
"If Einstein were alive today and learned science the boring way it is taught in so many U.S. schools, wouldn’t he have ended up at a Wall Street hedge fund rather than developing theories of relativity for a Nobel Prize?" says:
"Albert Einstein: 'for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect'"
I know I sound like splitting hairs here, but this didn't take more than a quick Google check. More importantly, it's always been very noticeable that he didn't get his prize for relativity, which everyone knows is his most important historical achievement (despite the photoelectric effect, requiring quanta of light, being his most self-admittedly "radical"). It's not hard to dig a little, e.g. this Discover piece from this year, based on research from Robert Marc Friedman (ironic -- wonder if he's a relative?) to get the story that the Nobel Committee actively didn't want him to get a prize for relativity, in a cultural context where "his theories were dismissed as 'world-bluffing Jewish physics' by some prominent German physicists, who claimed to practice "true" German science based on observations of the natural world and hypotheses that could be tested in a laboratory." And while his star was rising in the US, and the physics community pressed for him to get the prize, especially after Eddington confirming general relativity,
1921 was not the year, thanks to one stubborn senior member of the prize committee, ophthalmologist Allvar Gullstrand. "Einstein must never receive a Nobel Prize, even if the whole world demands it," said Gullstrand, according to a Swedish mathematician's diary dug up by Friedman. Gullstrand's arguments, however biased, convinced the rest of the committee. In 1921, the Swedish Academy of Sciences awarded no physics prize.
You get the picture. This is a great story about how a politicized culture worked against Einstein at his peak, such that an opthamologist could hold him back. At least one Friedman picked up on this.

Thursday, April 26, 2007

And You May Ask Yourself

How did I get here? Today I had a chance to try and explain my random walk to physics at a Career Panel held at CCNY. I was one of four speakers, the others being Rachel Connolly, Manager of Astrophysics Education at the Rose Center for Earth and Space, American Museum of Natural History, Joshua Spodek, Entrepreneurial Physicist (of linear zoetrope fame -- dig his news coverage), and Christina Tosti, Biomedical Engineer at Columbia. We had a great audience of about 40-50 CCNY students and staff, and about 90 minutes to share our stories, which had more than a few surprising wrinkles (major changes, aborted degrees, stints in the navy...). But I think it was fun for everyone there to see how our various choices got us to places we liked, and jobs we enjoyed.

My slides are online, posted here.

Thursday, April 19, 2007

Circus in the Mist

As New York suffered torrential rainfall, K and I managed to score a few cheap seats for the Ringling Bros. Barnum & Bailey circus down the street at Madison Square Garden. We had hoped to take some younger relatives but we still had an excellent time with just us adults. Clowns, elephants, acrobats, tigers - all there. You can find a few of my photos in a Flickr set.

Pop Quiz

Just poking around Cosmic Variance this morning (as if I have time, given my trip to Chicago this evening for a PHOBOS collaboration meeting...) and stumbled upon this: a cocktail party primer about string theory. Now, love it or hate it, string theory has captured most of the available mindshare for theoretical physics (kind of like the LHC in experimental physics), so it's great to see my people (i.e. RHIC) namechecked at the bottom:
Still, particle physics experiments being performed with collisions of very heavy ions at Brookhaven National Laboratory and with proton collisions at CERN could connect string theory with reality.
And we're already running. Now.

OK, so things aren't so easy when trying to connect experimental data with a theory that doesn't really predict anything yet. But as I've tried to point out where possible, people are clearly trying -- and it's interesting how even something which might be "wrong" (in the ontological sense) might nudge people intellectually in directions they hadn't considered, which may well lead us to something that is "right" (same sense). My money is that a similar story will play out at the LHC. No matter what will be observed, people will certainly try to say 1) it's nothing (e.g. DuRujula, below) 2) it's something out of the standard model so boring, or 3) it's exotic -- soit's proof of string theory! Of course there are worlds of exotica which people don't talk about anymore, and worlds to be discovered until the data is solidified (cf. LSND/MiniBoone).

All of this will prove (once again) that data rarely speaks by itself, and even if it tries, it tends to speak quite slowly...Ok, I really have to finish a few things now.

Tuesday, April 10, 2007


A few weeks ago, I mentioned the new "RHIC News" which
is already on its third issue. And this one is special, since yours truly has contributed a piece on the BNL involvement in the ATLAS heavy ion program. I was hoping to make the case that the LHC will be a natural, and essential, next step for the science we have been doing at RHIC (and at lower-energy facilities at CERN and BNL). Even better, all of the LHC detectors will be able to make contributions to this scientific effort, when the machine collides ions sometime in the next few years.

Now if only they could get those magnets sorted out...

Monday, April 09, 2007

On The Radio

It's becoming clear that the LHC, even with the setbacks of two weeks ago, is starting to gain a lot of mindshare in the media. To keep up with the one-article-per-week-it-seems, NPR's David Kestenbaum (a former physicist himself) has reported a piece from CERN. rapping with Alvaro de Rujula (who I heard give a great set of lectures on gamma ray bursts in Erice a few years back). While I'm not a big fan of the "nothing is interesting" (i.e. finding no Higgs might be more important than finding one) scenario, de Rujula clearly feels no need to hold back. Have a listen!