Higgs animations

The news recently from the LHC experiments hasn't been very exciting for my colleagues on the particle theory side of things (see for instance here for summaries and discussion). But via the clever chaps at ATLAS we do have a series of very nice gif animations showing how the evidence for the existence of the Higgs changed with time, as they collected more and more data.

This example shows the development of one plot, for the Higgs-to-gamma-gamma channel:

That's pretty cool. Also nice to see the gif format being put to better use than endless animations of cats doing silly things! (Though if you are a PhD student, you might find this use of gifs amusing ... )

Here's another one, this time for the decay channel to 4 leptons:

Note that in this case the scale on the y axis is also changing with time! There's a version of this animation with a fixed axis here, and one of the gamma-gamma channel with a floating axis here.

A real puzzle in cosmology: part I

In a previous post, I wrote about recent updates to the evidence from the cosmic microwave background for extra neutrino species. This was something that a lot of people in cosmology were prepared to get excited about, but I argued that reality turned out to be really rather boring. This is because the new data neither showed anything wrong with the current model of what the universe is made of, nor managed to rule out any competing models.

Today I'd like to write about something else, which currently is a really exciting puzzle. Measurements have been made of a particular cosmological effect, known as the integrated Sachs-Wolfe or ISW effect, and the data show a measured value that is five times larger than it should be if our understanding of gravitational physics, our model of the universe, and our analysis of the experimental method are correct. No one yet knows why this should be so. The point of this post is to try to explain what is going on, and to speculate on how we might hope to solve the puzzle. It has been written in a conversational format with the lay reader in mind, but there should be some useful information even for experts.

Before beginning, I should point out that this what a lot of my own research is about at the moment. In fact, this was the topic of a seminar I gave at the University of Helsinki last week (and much of this post is taken from the seminar). My host in Helsinki, Shaun Hotchkiss, with whom I have written two papers on this "ISW mystery", has also put up several posts about it at The Trenches of Discovery blog over the last year (see here for parts I, II, III, IV, V, and VI). I will be more concise and limit myself to just two!

Obviously you could view this as a bit of an effort at self-publicity. But at a time when, both in particle physics and cosmology, many experiments are disappointingly failing to provide much guidance on new directions for theorists to follow, this is one of the few results that could do so. (Unlike a lot of the rubbish you might read in other popular science reports, it also has a pretty good chance of being true.) So I won't apologise for it!

What is the integrated Sachs-Wolfe effect?

The entire universe is filled with very cold photons. These photons weren't always very cold; on the contrary, they are leftovers from the time soon after the Big Bang when the universe was still very young and very small and very hot, so hot that all the protons and electrons (and a few helium nuclei) formed a single hot plasma, the photons and electrons bouncing off each so often that they all had the same temperature. And as the universe was expanding, this plasma was also cooling, until suddenly it was cool enough for the electrons and protons to come together to form hydrogen atoms, without immediately getting swept apart again. And when this happened, the photons stopped bouncing off the electrons, and instead just continued travelling straight through space minding their own business, cooling as the universe continued to expand. (The neutrinos, which only interact weakly with other stuff, had stopped bouncing and started minding their own business some time before this.)

What I've just told you is a cartoon picture of the history of the early universe. These cooling photons streaming through space form the cosmic microwave background radiation, or CMB for short. They fill the universe, and they arrive at Earth from all directions – they even make up about 1% of the 'snow' you see on an (old-school) untuned TV set. 

The most important property of the CMB photons is that, to a very great degree of accuracy, they are all at the same temperature, whichever direction they come from. This is how we know that the universe used to be very hot, and how we learned that it has been expanding since then. It is also why we think it is probably very uniform. The second important property of CMB photons is that they are not all at the same temperature – by looking carefully enough with an extremely sensitive instrument, we can see tiny anisotropies in temperature across the sky. These differences in temperature are the signs of the very small inhomogeneities in the early matter-radiation plasma which are responsible for all the structure we see around us in the night sky today. When the photons decoupled from the primordial plasma, they kept the traces of the tiny inhomogeneities as they streamed across the universe. The matter, on the other hand, was subject to gravity, which took the small initial lumpiness and over billions of years caused it to become bigger and lumpier, forming stars, galaxies, clusters of galaxies and vast clusters of clusters.

The CMB sky as seen by the WMAP satellite. The colours represent deviations of the measured CMB temperature from the mean value – the CMB anisotropies (red is hot and blue is cold). This map uses the Mollweide projection to display a sphere in two dimensions. Image credit: NASA / WMAP Science team. 

Yes I knew that, but what is the integrated Sachs-Wolfe effect?

The nature of publications

A paper in the journal of Genome Biology and Evolution has been doing the rounds on the internet recently and was shown to me by a friend. It is titled "On the immortality of television sets: “function” in the human genome according to the evolution-free gospel of ENCODE", by Graur et al. The title is blunt enough, but the abstract is extraordinarily so. Let me quote the entire thing here:

A recent slew of ENCODE Consortium publications, specifically the article signed by all Consortium members, put forward the idea that more than 80% of the human genome is functional. This claim flies in the face of current estimates according to which the fraction of the genome that is evolutionarily conserved through purifying selection is under 10%. Thus, according to the ENCODE Consortium, a biological function can be maintained indefinitely without selection, which implies that at least 80 – 10 = 70% of the genome is perfectly invulnerable to deleterious mutations, either because no mutation can ever occur in these “functional” regions, or because no mutation in these regions can ever be deleterious. This absurd conclusion was reached through various means, chiefly (1) by employing the seldom used “causal role” definition of biological function and then applying it inconsistently to different biochemical properties, (2) by committing a logical fallacy known as “affirming the consequent,” (3) by failing to appreciate the crucial difference between “junk DNA” and “garbage DNA,” (4) by using analytical methods that yield biased errors and inflate estimates of functionality, (5) by favoring statistical sensitivity over specificity, and (6) by emphasizing statistical significance rather than the magnitude of the effect. Here, we detail the many logical and methodological transgressions involved in assigning functionality to almost every nucleotide in the human genome. The ENCODE results were predicted by one of its authors to necessitate the rewriting of textbooks. We agree, many textbooks dealing with marketing, mass-media hype, and public relations may well have to be rewritten.

Ouch.

The paper that Graur et al. implicitly deride as "marketing, mass-media hype and public relations" is one of series of publications in Nature (link here for those interested) by the ENCODE consortium. I'm not going to claim any expertise in genetics, though the arguments put forward by Graur appear sensible and convincing.¹ But I do think it is interesting that the ENCODE papers were published in Nature.

Nature is of course a very prestigious journal to publish in. In some fields, the presence or lack of a Nature article on a young researcher's CV can make or break their career chances. It is very selective in accepting articles: not only must contributions meet all the usual requirements of peer-review, they should also be judged to be in "the five most significant papers" published in that discipline that year. It has a very high Impact Factor rating, probably one of the highest of all science journals. In fact it is apparently one of the very few journals that does better on citation counts than the arXiv, which accepts everything.

But among some cosmologists, Nature has a reputation for often publishing claims that are over-exaggerated, describe dramatic results that turn out to be less dramatic in subsequent experiments, or are just plain wrong.² One professor even once told me – and he was only half-joking – that he wouldn't believe a particular result because it had been published in Nature.

It is easy to see how such things can happen. The immense benefit of a high-profile Nature publication to a scientist's career leads to a pressure to find results that are dramatic enough to pass the "significance test" imposed by the journal, or to exaggerate the interpretation of results that are not quite dramatic enough. On the other hand, if a particular result does start to look interesting enough for Nature, the authors may be – perhaps unwittingly – less likely to subject it to the same level of close scrutiny they would otherwise give it. The journal then is more reliant on its referee's to provide the scrutiny to weed out the hype from the substance, but even with the most efficient refereeing system in the world given enough submitted papers full of earth-shattering results, some amount of rubbish will always slip through.

I was thinking along these lines after seeing Graur et al.'s paper, and I was reminded of a post by Sabine Hossenfelder at the Backreaction blog, which linked to this recent pre-print on the arXiv titled "Deep Impact: Unintended Consequences of Journal Rank". As Sabine discusses, the authors point to quite a few undesirable aspects of the ranking of journals according to "impact factor", and the consequent rush to try to publish in the top-ranked journals. The publication bias effect (and in some cases, the subsequent retractions that follow) appear to be influenced to a degree by the impact factor of the journal in which the study is published. Another thing that might be interesting (though probably hard to check) is the link between the likelihood of scientists holding a press conference or issuing a press release to announce a result, and the likelihood of that result being wrong. I'd guess the correlation is quite high!

Of course the only real reason that the impact factor of the journal in which your paper is published matters is that it can be used a proxy indication of the quality of your work for the benefit of people who can't be bothered, or are unable, to read the original work and judge it on merit.

The other yardstick by which researchers are often judged is the number of citations their papers receive, which at least has the (relative) merit of being based on those papers alone, rather than other people's papers. Combining impact factor and citation count is even sillier – unless they are counted in opposition, so that a paper that is highly cited despite being in a low-impact journal gets more credit, and a moderately cited one in a high-impact journal gets less!

Anyway, bear these things in mind if you ever find yourself making a reflexive judgement about the quality of a paper you haven't read based on where it was published.

¹The paper includes a quote which pretty well sums up the problem for ENCODE:

"The onion test is a simple reality check for anyone who thinks they can assign a function to every nucleotide in the human genome. Whatever your proposed functions are, ask yourself this question: Why does an onion need a genome that is about five times larger than ours?"

²Cosmologists (the theoretical ones, at any rate) actually hardly ever publish in Nature. Even observational cosmology is rarely included. So you might regard this as a bit a of a case of sour grapes. I don't think that is the case, simply because it isn't really relevant to us. Not having a Nature publication is not a career-defining gap for a cosmologist: it's just normal.

Things to Read, 19th February

I have just arrived in Helsinki, where I am visiting current collaborators and future colleagues at the Helsinki Institute of Physics for a few days. I will give a talk next Wednesday, about which more later. In the meantime though, a quick selection of interesting things I have read recently:

• Did you know that about 6 million years ago, the Mediterranean sea is believed to have basically evaporated, leaving a dry seabed? This is called the Messinian Salinity Crisis, which I first learned about from this blog. There's also an animated video showing a hypothesised course of events leading to the drying up:
  
  
  
  
  Very soon after, the Atlantic probably came flooding back in over the straits of Gibraltar – an event known as the Zanclean Flood – and, according to some models, could have refilled the whole basin back up in a very short time. Spare a thought for the poor hippopotamuses that got stuck on the seabed ...

• A long feature in next month's issue of National Geographic Magazine is called The Drones Come Home, by John Horgan. Horgan has written a blog piece about this at Scientific American, which he has titled 'Why Drones Should Make You Afraid'. In the blog piece he has a bullet-point summary of the most disturbing facts about unmanned aircraft (military or otherwise) taken from the main piece. Some of these include:
  
  - "The Air Force has produced [a video showing] possible applications of Micro Air Vehicles [...] swarming out of the belly of a plane and descending on a city, where [they] stalk and kill a suspect."
  - "The Obama regime has quietly compiled legal arguments for assassinations of American citizens without a trial"
  - "The enthusiasm of the U.S. for drones has triggered an international arms race. More than 50 other nations now possess drones, as well as non-governmental militant groups such as Hezbollah."
  
  Scary stuff; worth reading the whole thing.

• I wrote some time ago about Niall Ferguson's argument about economics with Paul Krugman (this was in the context of a lot of nonsense Ferguson was coming up with at the time, both in his Reith lectures for the BBC, and in other publications). I just learned (via a post by Krugman, who also just learned) that Ferguson had already apparently admitted that he got it wrong, about a year ago. Krugman's response to that is here; I'd add that I notice this admission didn't seem to stop Ferguson continuing the same economic reasoning in his Reith lectures a few months later!

• A review of John Lanchester's new novel Capital, by Michael Lewis in the New York Review of Books. Quite often Almost always with the NYRB, I read reviews of books before I have read the actual book. In this case the result was to make me resolve to buy a copy.
  

Oxford Greenland Expedition

I sometimes wonder about the mix of topics I mention on this blog – is there too much physics, or not enough? Well, today's post is about something completely different: it is a straight-up publicity plug for the Oxford Greenland Expedition. This is a sea-faring and rock-climbing expedition organised by a group of students, and is exactly the kind of exciting exploratory adventure to which the title of this blog refers, so I'd like to support it as best I can. They have a fundraising page here. As I'll try to explain, I think it is a great plan, and they deserve all the support they can get!

The climbing members of the expedition team are all current or former students of Oxford University, and members of the Oxford University Mountaineering Club, whom I have known for a varying number of years (I've climbed on the same rope as many but not all of them). Between them, they have dreamt up an outrageously bold and brilliant plan for a climbing expedition in the Arctic – as the 'Objectives' page of their website puts it, their goals are:

1. Sail to Greenland!
2. Climb the Horn of Upernavik!
3. Sail north! Find an 800 m pillar! Climb it!
4. Explore for new climbs!
5. Sail back!

(The rest of the website is quite amusing too, if you poke around it.) The Horn of Upernavik appears to be a very dramatic 1000-metre-high piece of rock rising straight out of the sea near Uummannaq:

The Horn of Upernavik.

It has apparently also been the objective of several previous expeditions to climb the Horn, but none of them have succeeded. So if this team succeeds, they will be making (a small amount of) history ...

Although all are very good climbers and mountaineers, they are definitely firmly within the ranks of the enthusiastic amateurs rather than elite professionals. I think this makes the audacity of the undertaking all the more wonderful, and appealing to romantic ideals.

Incidentally, two of the members of this team (Ian Faulkner and Tom Codrington) were last year part of a different and equally inspiring expedition to Krygyzstan, during which they, along with Ian Cooper, made only the second ever free ascent of the Mirror Route or Rusyaev Route on Peak 4810, after Alex Lowe and Lynn Hill. A report of this climb and some other stuff they did was published here. So they've definitely got a track record with achieving amazing things!

Anyway, best of luck to the team in their efforts this summer!

Seeing neutrinos in the CMB

One of the really cool things about cosmology is the fact that you can look at the sky and use the cosmic microwave background to determine that there must be at least three generations of neutrinos, without having directly observed them in any ground-based experiments.

Well, actually we already knew that there were at least three neutrino generations from ground-based experiments before we had anywhere near the technological capability to determine this from the CMB, but it's arguably still pretty cool. What would inarguably be pretty amazing is if we could use CMB observations to prove that there were further, yet-undiscovered, generations of neutrinos that we could then go and look for elsewhere. Or, for a particular type of person, it might be quite satisfying to use the CMB to prove that there definitely weren't any more than the three generations we already know about, thus killing a lot of other people's pet theories stone dead.

All this is (somewhat) topical because of the release of new data from three experiments measuring the CMB: the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), that could in principle do something like this. Given my various recent blogging delays, however, I haven't been particularly quick about writing about this, and there are other good discussions elsewhere on the web, especially at Résonaances, that many readers will already have seen. I'm also afraid I don't have time for a layperson-level introduction to the topic right now. But there's a bit of a jumble of information from the different collaborations, some of it mildly contradictory, and in this post I'd like to – partly simply as a note for myself – summarise it all and sort it into a logical order.

In case you'd like to just see the executive summary, it is that – in my opinion – the new data doesn't tell us anything very interesting. For a fuller justification of this statement, keep reading.

Type Ia single degenerate survivors must be overluminous

I noticed a paper on the arXiv today with exactly this title (well, except that I removed the superfluous capitalisation of words), that is due to be published in the Astrophysical Journal. The abstract of the paper says:

In the single-degenerate (SD) channel of a Type Ia supernovae (SN Ia) explosion, a main-sequence (MS) donor star survives the explosion but it is stripped of mass and shock heated. An essentially unavoidable consequence of mass loss during the explosion is that the companion must have an overextended envelope after the explosion. While this has been noted previously, it has not been strongly emphasized as an inevitable consequence. We calculate the future evolution of the companion by injecting $2$-$6\times10^{47}$ ergs into the stellar evolution model of a $1\,M_\odot$ donor star based on the post-explosion progenitors seen in simulations. We find that, due to the Kelvin-Helmholtz collapse of the envelope, the companion must become significantly more luminous ($10$-$10^3\, L_\odot$) for a long period of time ($10^3$-$10^4$ years). The lack of such a luminous "leftover" star in the LMC supernova remnant SNR 0609-67.5 provides another piece of evidence against the SD scenario. We also show that none of the stars proposed as the survivors of the Tycho supernova, including Tycho G, could plausibly be the donor star. Additionally, luminous donors closer than $\sim10$ Mpc should be observable with the Hubble Space Telescope starting $\sim2$ years post-peak. Such systems include SN 1937C, SN 1972E, SN 1986G, and SN 2011fe. Thus, the SD channel is already ruled out for at least two nearby SNe Ia and can be easily tested for a number of additional ones. We also discuss similar implications for the companions of core-collapse SNe.

Now, technical scientific papers are full of jargon and maybe the meaning of that paragraph isn't immediately clear to everyone (there's an accompanying Youtube video purporting to explain the content of the paper, but I didn't think it quite achieved that aim!). But I think this result is really quite interesting and probably important in a broader cosmological sense.

New directions in a new year

Although we are already more than half-way through January, I'd like to say happy 2013 to all readers of this blog! Better late than never.

It won't have escaped the attention of regular visitors that the rate of posting new items here has significantly declined over the last few months, as exemplified by the belated new year's greetings. There is a good reason for this. It isn't that I haven't thought of any things to write about; on the contrary, I have had lots of ideas, but not enough time to write them up. Instead the hiatus has primarily been because I have been applying for a new postdoctoral job starting this coming October, and writing tailored job applications is an incredibly time-consuming process — much the same as in non-academic jobs, I suppose, though with the added annoyance that all the time spent writing in detail about what wonderful research you would do if hired is time not spent actually doing any research. Between those two competing claims for my attention and all the rest of real life, there was no time at all left for blogging.

However, the result of all this time spent applying is that I have now been offered, and accepted, a 2-year postdoc position to start in October at the University of Helsinki, in the group of Kari Enqvist. I have to say, I am very pleased about this, and not only because it means I needn't spend any further time on applications! In fact from a previous visit there, I know that the atmosphere in the Helsinki research group is one that I will enjoy very much.

I understand that to people outside academic physics circles, applying in about November (in fact some deadlines this year were even slightly earlier) for a job due to start fully 11 months later might seem a little odd. But that is the way the system works, and it probably isn't the only odd thing about physicists anyway. On the bright side though, it does mean that — as in this case — the question of where in the world one is moving to can all be settled by January, leaving plenty of time to plan the move, both in academic and purely logistical terms.

Anyway, now that this business is over, you can expect to see a slightly improved rate of posting here.

More new physics prizes

The news today in physics, reported by the New York Times and Peter Woit, is that Yuri Milner, the Russian billionaire physics enthusiast, has announced a new set of prizes for fundamental physics. I wrote a little about the previous award of prizes here. These prizes are somewhat less generous than those announced over the summer (which were worth \$3 million each); this time only Stephen Hawking receives that amount, and the others get a smaller share. Woit typically notes that almost all the non-experimental recipients have some connection to string theory.

But the other interesting thing about the new prizes is that in this round, some experimentalists have actually been included. Of course all of them are involved with the LHC at CERN: no surprise there, given Milner's personal interests in physics.

What I do find rather noteworthy, however, is the way in which the prizes have been divided. $1 million is to be divided between the current and former ATLAS spokespersons Fabiola Gianotti and Peter Jenni, and another million between CMS current and ex-spokepersons Joe Incandela, Michel Della Negra and Tejinder Virdee. Now I'm not very knowledgeable about the organisational structure or the division of labour in these experiments, but each experiment has roughly 3000 scientists working on it and everything I had read about them in relation to speculation about a possible Nobel award suggested that there was no real way to single out the contribution of any individuals out of these thousands as being especially more worthy than any other.

It does appear that Milner has found a way to do this though: pick the spokesperson elected by the experiment. Now I wonder what the reaction to this is at ATLAS and CMS. Is this regarded as fair? Do the spokespersons really make a bigger contribution to the discovery of the Higgs? I really don't know but I'd be interested to learn what people think. I know some of the readers of this blog are part of the ATLAS and CMS collaborations — if any of you have an opinion, please do share it through the comment box!

Update: Via Shaun in the comments, there is interesting news about what the current spokespersons intend to do with their money. Also, Tommaso Dorigo gives his opinion on the matter here; I have to say my views are rather more in line with those expressed in the comment by Bernhard on that blog.

Less serious update: An anonymous friend in the ATLAS group says "I can't believe Fabiola has had her choice of font vindicated in this way."

Things to Read, 2nd December

Time for another collection of worthwhile links from elsewhere on the internet.

Science links:

• Jester at Résonaances has been producing a series of very good informative posts from the frontlines of particle physics: particularly worth reading are this summary of the state of play with the "detection" of dark matter by the Fermi telescope, this explanation on what is and isn't contained in the new Higgs analyses from the LHC, including intriguing information on why some data hasn't yet been updated, and this take on the relevance of the LHCb measurements of Bs meson decay for supersymmetry (which has been the subject of a lot of hype in the popular press).
• Speaking of the popular press, Time magazine has seen fit to nominate the Higgs boson as one of the candidates for "person of the year" (you can vote for it if you like). As if that weren't ridiculous enough, the accompanying description must surely qualify as one of the worst pieces of science journalism ever: literally every single sentence is wrong. Worth a look — even if you're not a physicist, you might be able to spot the mistakes.
• I've recently discovered a series of super-slow-motion videos of lightning strikes knocking around on the internet. These are shot at several thousand frames per second, and really show the details of how the charge leaders meander towards the ground before the main secondary stroke follows. Even more interesting are some videos showing lightning travelling upwards, from ground to cloud. Here's a video:
  
  
  and here's a popular-level description of the phenomenon.
• Another particularly cool video I saw some time ago was this one, showing the synchronisation of 32 metronomes placed on a flexible platform:
  
  

Other links:

• This one is part science, part history and part politics. Have you ever wondered what the connection is between prehistoric plankton from the Cretaceous era, and the distribution of votes for Obama? Of course you haven't, but now you can find out anyway. 
• On a more serious note: one of the striking things about the US election was how completely wrong Republicans and the right-wing were in their predictions of the outcome. Especially so since there were so many people who were able, by simple analysis of the available facts, to arrive at predictions that were much better (Nate Silver, for one). There is lots to be said about this, I suppose. One striking observation, which maybe hasn't been made enough of, is the hope that people realise that if the right-wing media can spout such rubbish (not to say lies) about the polls, perhaps the rest of what they say is rubbish too. 
• And following on from that, an interesting article from someone on the right of American politics: The Revenge of the Reality-Based Community.
• It's not just in the US that facts have a well-known anti-right-wing bias of course. And it's not just US right-wing politicians who dislike them. When economist Jonathan Portes of the National Institute for Economic and Social Research appeared before the UK parliament and explained some fairly elementary economics that happens to contradict the ideology of the Conservative Party, he received thinly veiled threats from MP Jesse Norman (watch; transcript). This drives other economists to express their equally thinly veiled contempt. Norman responds, and Wren-Lewis dismisses him again.
• And finally, something more cheery: some time ago I posted the story about the dog who climbed a mountain with me in the Himalayas. I thought that dog was pretty awesome, but then I saw this dog, who seems to have done an even harder climb!
  
  
  
  (She does seem to have a protective harness though, which probably gives her an unfair advantage ...)