Andrew Jaffe: Leaves on the Line

A quick pointer to Initiative for Cosmology (iCosmo). The website brings together a bunch of useful calculations for physical cosmology — relatively simple quantities like the relationship between redshift and distance, and also more complicated ones like the power spectrum of density perturbations (which tells us the distribution of galaxies on the largest scales in the Universe) and quantities derived from that like the distortions in the shapes of galaxies due to gravitational lensing, when the path of light from galaxies is perturbed by intervening mass in the Universe. Combined with good documentation and tutorials (and downloadable source), it makes a good companion to sites such as LAMBDA’s CMB toolbox, which provides similar services targeted specifically at Cosmic Microwave Background science. iCosmo looks like it will be useful for researchers in the field as well as students, so thanks and congratulations to its creators (I’d like to point directly at the page listing them, but that doesn’t seem to be possible… instead, there’s a discussion forum at CosmoCoffee.).

The Wakeham Review on the state of UK Physics has been released. Andy Lawrence has a good executive summary and The Guardian an overview. It seems to be positive about the state of physics overall, but perhaps lacks the rage and invective the community was hoping for. I am travelling but will try to digest it; let this serve as a placeholder until then.

So, apologies for taking so long between posts. For now, I’ll blame twitter and its ADD version of blogging, because that at least lets me point to an interesting meeting that went on last week: the .Astronomy Conference on Networked Astronomy and the New Media. the conference brought together several related strands of astronomical computing, from the grid (the Virtual Observatory), to “citizen astronomy” (Galaxy Zoo, which is apparently being upgraded to “Universe Zoo”, Google Sky, and blogs and podcasts), to hacks and mashups built on top of current bits of distributed infrastructure, not to mention twitter itself. (Connectivity is terrible here, but much of the material from the conference is available from the conference site.)

Unfortunately, I spent that time in a meeting room doing my part on STFC committees to keep the UK physics funding process moving along as well as possible during these still-troubled times.

Now, I’m in the Macedonian Greek city of Thessalonika, lucky enough to have been invited to give a talk at From the Antikythera Mechanism to Herschel and Planck: 2500 Years of Observational Astronomy, organized by one of Imperial’s postdocs. I won’t let it go to my head, but it’s nice being treated as someone vaguely important: lunch with the vice-mayor, nice hotel, and amusing Thessaloniki swag to cart home (although when Ute Lemper came to sing she had lunch with the Mayor himself…). My talk is this evening, but the rain outside is precluding much local exploration, but at least I have some time to finish my talk (and write this).

For me, home for about 12 hours tomorrow night, and then off to a Planck meeting in Rome and then Palermo.

Finally let me also welcome Peter Coles to the astro blogosphere. His current prolixity is putting me to shame.

I’m at a meeting in Cambridge this week, discussing details of the way matter is arranged in the Universe, and the insight that gives us into the fundamental physics of the Universe. Many of us have got up a bit early to watch the BBC coverage of the first beams at the LHC, since CERN’s own coverage is overloaded. (It so happens that I’m at DAMTP, Stephen Hawking’s home base, but he has probably wisely decided to stay in bed.)

So far they’ve got the beam half-way around.

We cosmologists are always pleased that almost all of the PR descriptions are about the kind of work that we do: recreating the conditions of the early Universe and finding dark matter.

First mention of the Higgs Boson… but very quickly followed by more cosmology: how will the Universe end?

Pointing out that we’ll have to wait for December or so until we actually get two-beam collisions at full energy.

But now it’s time to go back to my meeting…

And now they’ve apparently had beams going both directions…

PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) is a Russian-Italian satellite measuring the composition of cosmic rays. One of the motivations for the measurements is the indirect detection of dark matter — the very-weakly-interacting particles that make up about 25% of the matter in the Universe (with, as I’m sure you all know by now) normal matter about 5% and the so-called Dark Energy the remaining 70%. By observing the decay products of the dark matter — with more decay occurring in the densest locations — we can probe the properties of the dark particles. So far, these decays haven’t yet been unequivocally observed. Recently, however, members of the PAMELA collaboration have been out giving talks, carefully labelled “preliminary”, showing the kind of excess cosmic ray flux that dark matter might be expected to produce.

But preliminary data is just that, and there’s a (usually) unwritten rule that the audience certainly shouldn’t rely on the numerical details in talks like these. Cirelli & Strumia have written a paper based on those numbers, “Minimal Dark Matter predictions and the PAMELA positron excess” (arXiv:0808.3867), arguing that the data fits their pet dark-matter model, so-called minimal dark matter (MDM). MDM adds just a single type of particle to those we know about, compared to the generally-favored supersymmetric (SUSY) dark matter model which doubles the number of particle types in the Universe (but has other motivations as well). What do the authors base their results on? As they say in a footnote, “the preliminary data points for positron and antiproton fluxes plotted in our figures have been extracted from a photo of the slides taken during the talk, and can thereby slightly differ from the data that the PAMELA collaboration will officially publish” (originally pointed out to me in the physics arXiv blog).

This makes me very uncomfortable. It would be one thing to write a paper saying that recent presentations from the PAMELA team have hinted at an excess — that’s public knowledge. But a photograph of the slides sounds more like amateur spycraft than legitimate scientific data-sharing.

Indeed, it’s to avoid such inadvertent data-sharing (which has happened in the CMB community in the past) that the Planck Satellite team has come up with its rather draconian communication policy (which is itself located in a password-protected site): essentially, the first rule of Planck is you do not talk about Planck. The second rule of Planck is you do not talk about Planck. And you don’t leave paper in the printer, or plots on your screen. Not always easy in our hot-house academic environments.

Update: Bergstrom, Bringmann, & Edsjo, “New Positron Spectral Features from Supersymmetric Dark Matter - a Way to Explain the PAMELA Data?” (arXiv: 0808.3725) also refers to the unpublished data, but presents a blue swathe in a plot rather than individual points. This seems a slightly more legitimate way to discuss unpublished data. Or am I just quibbling?

Update 2: One of the authors of the MDM paper comments below. He makes one very important point, which I didn’t know about: “Before doing anything with those points we asked the spokeperson of the collaboration at the Conference, who agreed and said that there was no problem”. Essentially, I think that absolves them of any “wrongdoing” — if the owners of the data don’t have a problem with it, then we shouldn’t, either (although absent that I think the situation would still be dicey, despite the arguments below and elsewhere). And so now we should get onto the really interesting question: is this evidence for dark matter, and, if so, for this particular model. (An opportunity for Bayesian model comparison!?)

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It’s making the science-blogging rounds today that Obama has answered the questions posed as Science Debate 2008, questions on education, health care, stem cells and, of course, climate. He supports all the right scientific positions, and says several times that he will increase funding for basic research overall, but most importantly acknowledges and condemns the ideological and political interference that has plagued US research during the Bush administration.

McCain will, apparently, follow with his answers soon.

Meanwhile, here in the UK, the lengthily-named Department for Innovation, University and Skills (DIUS) is holding a consultation on Science and Society where you can answer questions like “How should scientists be rewarded for their efforts to communicate science to the public?” (I’m thinking big wads of cash.)

NASA’s latest space-based telescope has, until now, been known as the Gamma-Ray Large Area Space Telescope (GLAST). Today, they announced the very first results, and renamed it the Fermi Space Telescope, after physicist Enrico Fermi. Fermi was one of the pioneers of modern particle physics, part of the Manhattan Project generation that created the fundamental theories and techniques that we still use today, although he died sadly young before he could see the fruition of his work in today’s standard model of particle physics. He also thought hard about a number of more speculative issues, including wondering why, if life is common in the Universe, we haven’t met any other sentient creatures yet (a question known in fact as the Fermi Paradox) — and worried that the answer might be that civilizations tend to blow themselves up.

Today’s results came in the form of an all-sky map. The band in the center is gamma-ray emission from the Milky Way galaxy, and three of the four bright spots are pulsars — fast-spinning, magnetized neutron stars, and the fourth is a kind of distant active galaxy known as a “Blazar”.

I wonder how long before someone will compare the GLAST (Fermi) maps with the microwave-band maps from WMAP like this one:

The way gamma rays are created is very different from the emission microwaves, but any soup of gas, dust, stars and magnetic fields is likely to produce both.

Just as exciting as these maps is GLAST’s ability to find Gamma-Ray Bursts, some of the most energetic objects in the Universe, whose mechanisms are still poorly understood, and which may let us peer to the epoch of the formation of the very first objects.

(All images courtesy NASA.)

For some reason a lot of music books have percolated to the top of my bedstand pile recently. I just finished Alex Ross’ magisterial and definitive The Rest is Noise, a history of 20th Century “Western Classical” music. (Let’s pause for a moment and praise the genius of that title, by the way.) The book starts with Strauss, Mahler and Debussy and ends with John Adams and some of my recent obsessions: Arvo Pärt, Steve Reich and Olivier Messiaen, whose Quartet for the End of the Time is at the Proms next week. (For me, really a neophyte with this kind of music, the book was an ideal companion to Paul Morley’s Words and Music, which turned me onto this music by reimagining the history of rock’n’roll as if driven not by the blues but by the resolutely white-boy classical tradition: it starts and ends with Alvin Lucier’s minimalist “I am Sitting in a Room” and Kylie’s “Can’t Get You Out of My Head”.)

But the centerpiece of Ross’s book is three chapters on the way politics drove the musical agenda (or at least tried to) in mid-century Germany, America and the Soviet Union. The unspoken but eventually obvious point comes through, that the music can’t help be of its place and time, a product of the world around it, but that our duty is just to listen, not forgetting the history, but not paying it too much attention, either.

I’ve also been reading Love is a Mix Tape, Rob Sheffield’s music-tinged memoir, concentrating on the loss of his first wife, Renée, far too young. I’m lucky enough to have known Rob for more than 20 years, and that made the book both hard to put down and, when the going got tough, recalling for me the day when Rob phoned to tell me the terrible news about Renée, hard to pick up. But it’s a lovely, moving, book, managing to set down the emotional pull of music’s private meaning and the way it connects to the people listening with us, even on an iPod hundreds or thousands of miles away. (You can hear Rob reading some excerpts at the book’s site.; there’s a wonderful NPR interview with Rob, too.)

Now, I’m on to Simon Armitage’s Gig, also a memoir, this time by a music-obsessed British poet.

(By the way, does anyone have a definitive attribution for “Writing about music is like dancing about architecture”? I’ve mostly heard Elvis Costello, but also Steve Martin.)

There’s a new Google-competing search engine called Cuil (which I guess is meant to be pronounced as slacker-speak “kewl” or something). If I search for myself on it, my Imperial homepage comes up first, but for some reason accompanied by this picture. I promise that’s not me. Just as strange, a picture that is of me comes up next to a blurb for a book written by another Andrew Jaffe who happens to be the director of the Clio Awards for advertising (there are a few of us Andrew Jaffes out there, but I’m egotistically happy to tell you that I’m top in most search engines). But I’m happiest about the cover shot from Muscle Magazine (not me either).