The Ashes Return

Posted in Cricket with tags on August 23, 2009 by telescoper

Just a short note, for posterity more than anything else. England have won back The Ashes from Australia!!

The final test match at the Oval ended this evening, with England finally knocking over the last Australian wicket, the gallant Mike Hussey who scored a defiant 121 today. Set to make a total of 546 to win in the second innings, Australia got to a creditable 348 all out but it was always going to be too stiff a target on a pitch that has been visibly deteriorating since the first day.

I’ve actually been struggling since last Friday with a nasty stomach bug, otherwise I might have had time to blog a bit more about this match. I have to say the tension as England’s fortunes have ebbed and flowed hasn’t done much for my convalescence either! Earlier this afternoon Australia looked very comfortable, in fact. Two run outs set them back a bit , but even so England were making heavy work of bowling them out. Cue Steve Harmison (who  had a mediocre match until that point) and Graham Swann (who had an excellent game) , both of them weighing in with wickets, as Australia finally keeled over, from 327-5 to 348 all out. Indeed Harmison took two wickets with consecutive balls and could have finished the match and won the Ashes with a hat-trick.

Although the game finished (just) inside four days instead of carrying on into the fifth, I was struck by how much the pattern of this match followed that of the Lord’s Test  that I was lucky enough to see a part of. In particular, both games turned on poor first innings with the bat for the Australians.

As for the series, we now all know just how important that last day at Cardiff was! With England winning at Lord’s, a draw at Edgbaston and Australia trouncing England at Headingley, it was only still 1-1 because of that staunch rearguard with the bat by England’s bowlers, Anderson and Panesar. Without them the series would have been 2-1 to Australia. If the series is tied the Ashes stay with whoever held them before the series started, so  a draw in this match would have meant Australia retaining them,  but England won and took the series 2-1. Although Monty Panesar didn’t play at the Oval, let’s not forget how important his contribution was.

 I don’t think this series produced as much quality cricket as the epic struggle of 2005. In that series the games were closer and on most occasions the game went into the final day with any result possible, which is actually quite a rare occurence in Test cricket.  But the result is the same and the celebrations will be similar.

If England can sort out their batting problems (especially at No. 3) then they could become a really good side. They’ll need to be when they travel to South Africa later this year. How about bringing Monty in at No. 3?

The football season is also under way and that’s the last Test cricket of the summer. Time passes. I enjoy football , especially when Newcastle United are winning – an all too rare experience but one which is happening these days – but I have to say that nothing can match Test cricket for drama and entertainment. If football is like a rock concert, then cricket is grand opera.

10 Comments »

Giant Steps

Posted in Jazz with tags , on August 21, 2009 by telescoper

After all the griping about musical taste  in two of my earlier posts this week (here and here), it’s probably good to put something up which I think is a masterpiece. You may, of course, disagree….

I came across this on Youtube a while ago. It made me think of the hours I spent trying to transcribe a Johnny Dodds clarinet solo from an old record, and that came out as a single page of music!

Here’s what the incredible virtuosity of John Coltrane‘s tenor sax playing looks like when written down. Or not quite. For some reason, the transcription is done as if the instrument is in Concert Pitch (C) whereas the tenor saxophone is a transposing instrument (B-flat). This means when you play what is written as C on the stave what actually comes out as B-flat, etc. Music for such instruments has to be written taking this into account, but this transcription doesn’t do so. There used to be (and probably still are, here and there) C-melody saxophones but they’re not very popular, and John Coltrane certainly wasn’t playing one on this track!

Neverthless, the speed and inventiveness of his playing is just amazing to behold. The tune is a Coltrane original which involves an unusual (and difficult to play) chord progression based on three keys shifted by major thirds.

It’s  called Giant Steps…

3 Comments »

Much Ado About a Null Result

Posted in Science Politics, The Universe and Stuff with tags , , , on August 20, 2009 by telescoper

In today’s Nature there’s an article outlining the current upper limits on the existence of a stochastic cosmological background of gravitational waves. The basis of the analysis presented in the paper is a combination of data from two larger international collaborations, called VIRGO and LIGO. Cardiff University is a member of the latter, so I suppose I should be careful about what I say…

These experiments have achieved incredible sensitivity – they can measure distortions that are a tiny fraction of an atomic nucleus in scale – but because gravity is such a very weak force they still haven’t managed to find direct evidence of gravitational waves. The next generation of these laser interferometers – Advanced LIGO – should get within hailing distance of a detection but in the meantime we have to do with upper limits. Since the sensitivity of the instruments is so well calibrated, the lack of a signal can yield interesting information. The Nature paper is quite interesting in that it summarizes the constraints that can be placed in such a way on some models of the early Universe. Mostly, though, these are “exotic” models that have already been excluded by other means. If I’ve got my sums right the stochastic gravitational wave background expected to be produced within the standard “concordance” cosmology, in which gravitational wave modes are excited by cosmic inflation, is at least three orders of magnitude lower than current experimental sensitivity.

I can’t resist including the following excerpts from a press release, produced by the Media Relations Department at Caltech whose spin doctors have apparently been hard at work.

Pasadena, Calif.—An investigation by the LIGO (Laser Interferometer Gravitational-Wave Observatory) Scientific Collaboration and the Virgo Collaboration has significantly advanced our understanding the early evolution of the universe.

Analysis of data taken over a two-year period, from 2005 to 2007, has set the most stringent limits yet on the amount of gravitational waves that could have come from the Big Bang in the gravitational wave frequency band where LIGO can observe. In doing so, the gravitational-wave scientists have put new constraints on the details of how the universe looked in its earliest moments.

Much like it produced the cosmic microwave background, the Big Bang is believed to have created a flood of gravitational waves—ripples in the fabric of space and time—that still fill the universe and carry information about the universe as it was immediately after the Big Bang. These waves would be observed as the “stochastic background,” analogous to a superposition of many waves of different sizes and directions on the surface of a pond. The amplitude of this background is directly related to the parameters that govern the behavior of the universe during the first minute after the Big Bang.

and

“Since we have not observed the stochastic background, some of these early-universe models that predict a relatively large stochastic background have been ruled out,” says Vuk Mandic, assistant professor at the University of Minnesota.

“We now know a bit more about parameters that describe the evolution of the universe when it was less than one minute old,” Mandic adds. “We also know that if cosmic strings or superstrings exist, their properties must conform with the measurements we made—that is, their properties, such as string tension, are more constrained than before.”

This is interesting, he says, “because such strings could also be so-called fundamental strings, appearing in string-theory models. So our measurement also offers a way of probing string-theory models, which is very rare today.”

“This result was one of the long-lasting milestones that LIGO was designed to achieve,” Mandic says. Once it goes online in 2014, Advanced LIGO, which will utilize the infrastructure of the LIGO observatories and be 10 times more sensitive than the current instrument, will allow scientists to detect cataclysmic events such as black-hole and neutron-star collisions at 10-times-greater distances.

“Advanced LIGO will go a long way in probing early universe models, cosmic-string models, and other models of the stochastic background. We can think of the current result as a hint of what is to come,” he adds.

“With Advanced LIGO, a major upgrade to our instruments, we will be sensitive to sources of extragalactic gravitational waves in a volume of the universe 1,000 times larger than we can see at the present time. This will mean that our sensitivity to gravitational waves from the Big Bang will be improved by orders of magnitude,” says Jay Marx of the California Institute of Technology, LIGO’s executive director.

“Gravitational waves are the only way to directly probe the universe at the moment of its birth; they’re absolutely unique in that regard. We simply can’t get this information from any other type of astronomy. This is what makes this result in particular, and gravitational-wave astronomy in general, so exciting,” says David Reitze, a professor of physics at the University of Florida and spokesperson for the LIGO Scientific Collaboration.

If hyperbole is what you’re looking for, go no further. There’s nothing wrong with presenting even null results in a positive light but, I don’t think this paints a very balanced picture of the field. For examples, early Universe models involving cosmic strings were already severely constrained before these results, so we know that they don’t have a significant effect on the evolution of cosmic structure anyway.

Clearly the political intention was to flag the importance of Advanced LIGO, although even that will probably be unable to detect the cosmological gravitational-wave background.  Overstatements contained in press releases of this type usually prove counterproductive in the long run.

5 Comments »

Beginning Again

Posted in Books, Talks and Reviews, The Universe and Stuff with tags , on August 19, 2009 by telescoper

I keep finding old forgotten bits and pieces – especially book reviews – on my computer. This one is about five years old but I thought I might as well put it on here to save having to think of anything else for today. It’s also a little bit topical because the author, Simon Singh, has recently been the subject of much discussion on this blog (here and here).

This piece was eventually published in an edited form as as Nature 432, 953-954 (23 December 2004) | doi:10.1038/432953b; Published online 22 December 2004.

BOOK REVIEWED–Big Bang: The Most Important Scientific Discovery of All Time and Why You Need to Know About It

by Simon Singh
Fourth Estate: 2004. 544 pp. £20, $27.95

When the British astrophysicist Fred Hoyle coined the phrase ‘Big Bang’ to describe the rival to his beloved ‘steady state’ theory of the Universe, he meant it to be disparaging. It was bad enough for Hoyle that his pet theory turned out to disagree with astronomical observations, but it must have been especially galling that his cosmological adversaries embraced his derisive name. The tag has since spread into the wider cultural domain — nowadays even politicians have heard of the Big Bang.

But what is the Big Bang? In a nutshell, it is the idea that our Universe — space, time and all its matter content — was born in a primordial fireball, from which the whole caboodle has been expanding and cooling ever since. Pioneering theorists such as Aleksander Friedmann and Georges Lemaître derived mathematical solutions of Einstein’s field equations that could be used to describe the evolution of a Big Bang Universe. These models involve a creation event, in which space-time and matter-energy sprang into existence to form our Universe. We are still in the dark about how this happened, but we think it took place about 14 billion years ago.

Edwin Hubble’s discovery of the recession of distant galaxies gave support to the idea that the Universe was expanding, but the notion that it might be evolving from a hot beginning was rejected by many theorists, including Hoyle. He favoured a model in which the origin of matter was not a single event but a continuous process in which atoms were created to fill in the gaps created by cosmic expansion. The battle between these competing views of creation raged until the accidental discovery in 1965 of the cosmic microwave background radiation, which marked the beginning of the end for the steady-state theory.

This conflict between the two theories plays a central role in Simon Singh’s book Big Bang. His previous books, Fermat’s Last Theorem and The Code Book, succeeded admirably in bringing difficult mathematical subjects to a popular readership, using a combination of accessible prose, a liberal sprinkling of jokes and a strong flavouring of biographical anecdotes. The recipe for his new book is similar.

In Big Bang, Singh uses the historical development of modern cosmological theory as a case study for how scientific theories are conceived, and how they win or lose acceptance. He rightly points out that science rarely proceeds in an objective, linear fashion. Correct theories are often favoured for the wrong reasons; observations and experiments are frequently misinterpreted; and sometimes force of personality holds sway over analytic reason. Because cosmology has such ambitious goals — to find a coherent explanation for the entire system of things and how it has evolved — these peculiarities are often exaggerated. In particular, cosmology has more than its fair share of eccentric characters, providing ample illustration of the role of personal creativity in scientific progress.

This very well written book conveys the ideas underpinning cosmological theory with great clarity. Taking nothing for granted of his readership, Singh delves into the background of every key scientific idea he discusses. This involves going into the history of astronomical observation, as well as explaining in non-technical language the principles of basic nuclear physics and relativity. The numerous snippets of biographical information are illuminating as well as amusing, and the narrative is driven along by the author’s own engaging personality.

However, even as a fan of Singh’s previous books, I have to admit that, although this one has many strengths, I found it ultimately rather disappointing. For one thing, there isn’t anything in this book that could be described as new. The book follows a roughly historical thread from pre-classical mythology to the middle of the twentieth century. This is a well-worn path for popular cosmology, and the whole thing is rather formulaic. Each chapter I read gave me the impression that I had read most of it somewhere before. It certainly lacks the ground-breaking character of Fermat’s Last Theorem.

The past ten years in cosmology have witnessed a revolution in observation that has, among many other things, convinced us of the existence of dark energy in the Universe. Theory has also changed radically over this period, largely through the introduction of ideas from high-energy physics, such as superstring theory. Indeed, some contemporary Big Bang models bear a remarkable resemblance to the steady-state universe, involving the continuous creation not of mere atoms, but of entire universes.

Frustratingly, virtually all the exciting recent developments are missing from this book, which leaves off just when things started to get interesting, with the COBE satellite in 1992. Readers who want to know what is going on now in this field should definitely look elsewhere. The processes of cosmic discovery and controversy are ongoing, not just relics of the past.

3 Comments »

Critical Theory

Posted in Art, Music, Science Politics with tags , , , , , on August 18, 2009 by telescoper

Critics say the stangest things.

How about this, from James William Davidson, music critic of The Times from 1846:

He has certainly written a few good songs, but what then? Has not every composer that ever composed written a few good songs? And out of the thousand and one with which he deluged the musical world, it would, indeed, be hard if some half-dozen were not tolerable. And when that is said, all is said that can justly be said of Schubert.

Or this, by Louis Spohr, written in 1860 about Beethoven’s Ninth (“Choral”) Symphony

The fourth movement is, in my opinion, so monstrous and tasteless and, in it’s grasp of Schiller’s Ode, so trivial that I cannot understand how a genius like Beethoven could have written it.

No less an authority than  Grove’s Dictionary of Music and Musicians (Fifth Edition) had this to say about Rachmaninov

Technically he was highly gifted, but also severely limited. His music is well constructed and effective, but monotonous in texture, which consists in essence mainly of artificial and gushing tunes…The enormous popular success some few of Rachmaninov’s works had in his lifetime is not likely to last and musicians regarded it with much favour.

And finally, Lawrence Gillman wrote this in the New York Tribune of February 13 1924 concerning George Gershwin’s Rhapsody in Blue:

How trite and feeble and conventional the tunes are; how sentimental and vapid the harmonic treatment, under its disguise of fussy and futile counterpoint! Weep over the lifelessness of the melody and harmony, so derivative, so stale, so inexpressive.

I think I’ve made my point. We all make errors of judgement and music critics are certainly no exception. The same no doubt goes for literary and art critics too. In fact,  I’m sure it would be quite easy to dig up laughably inappropriate comments made by reviewers across the entire spectrum of artistic endeavour. Who’s to say these comments are wrong anyway? They’re just opinions. I can’t understand anyone who thinks so little  of Schubert, but then an awful lot of people like to listen what sounds to me to be complete dross. There even appear to be some people who disagree with the opinions I expressed yesterday!

What puzzles me most about the critics is not that they make “mistakes” like these – they’re only human after all – but why they exist in the first place. It seems extraordinary to me that there is a class of people who don’t do anything creative themselves  but devote their working lives to criticising what is done by others. Who should care what they think? Everyone is entitled to an opinion, of course, but what is it about a critic that implies we should listen to their opinion more than anyone else?

(Actually, to be precise, Louis Spohr was also a composer but I defy you to recall any of his works…)

Part of the idea is that by reading the notices produced by a critic the paying public can decide whether to go to the performance, read the book or listen to the record. However, the correlation between what is critically acclaimed and what is actually good (or even popular) is tenuous at best. It seems to me that, especially nowadays with so much opinion available on the internet, word of mouth (or web) is a much better guide than what some geezer writes in The Times. Indeed, the   Opera reviews published in the papers are so frustratingly contrary to my own opinion that I don’t  bother to read them until after the performance, perhaps even after I’ve written my own little review on here.  Not that I would mind being a newspaper critic myself. The chance not only to get into the Opera for free but also to get paid for spouting on about afterwards sounds like a cushy number to me. Not that I’m likely to be asked.

In science,  we don’t have legions of professional critics, but reviews of various kinds are nevertheless essential to the way science moves forward. Applications for funding are usually reviewed by others working in the field and only those graded at the very highest level are awarded money.  The powers-that-be are increasingly trying to impose political criteria on this process, but it remains a fact that peer review is the crucial part of the process. It’s not just the input that is assessed either. Papers submitted to learned journals are reviewed by (usually anonymous)  referees, who often require substantial changes to be made the work can be accepted for publication.

We have no choice but to react to these critics if we want to function as scientists. Indeed, we probably pay much more attention to them than artists do of critics in their particular fields. That’s not to say that these referees don’t make mistakes either. I’ve certainly made bad decisions myself in that role,  although they were all made in good faith. I’ve also received comments that I thought were unfair or unjustifiable, but at least I knew they were coming from someone who was a working scientist.

I suspect that the use of peer review in assessing grant applications will remain in place for a some considerable time. I can’t think of an alternative, anyway. I’d much rather have a rich patron so I didn’t have to bother writing proposals all the time, but that’s not the way it works in either art or science these days.

However, it does seem to me that the role of referees in the publication process is bound to become redundant in the very near future. Technology now makes it easy to place electronic publications on an archive where they can be accessed freely. Good papers will attract attention anyway, just as they would if they were in refereed journals. Errors will be found. Results will be debated. Papers will be revised. The quality mark of a journal’s endorsement is no longer needed if the scientific community can form its own judgement, and neither are the monstrously expensive fees charged to institutes for journal subscriptions.

26 Comments »

Music 101

Posted in Biographical, Music with tags , , , , , , , , , , on August 17, 2009 by telescoper

Regular readers of this blog will know that I’m a very laid-back kind of guy, unlikely to take an irrational dislike to anything or anyone and in possession of an easy-going and tolerant nature not disposed to any form of grumpiness.

However, I’ve decided to celebrate the fact that I’ve finished marking all my resit examinations by letting my hair down a bit and giving you a list of my musical pet hates. The title is an allusion to  George Orwell’s 1984, wherein Room 101 was a personalised torture chamber containing a prisoner’s own worst nightmare. Here I’ve confined myself to music. I was going to include rap but, as I said, I’ve decided to confine myself to music.

Brass Bands. I don’t mind brass bands – particularly colliery bands and the Salvation Army band – at Christmas or for singing hymns to, but I’ve put them on my list for the excruciating brass-band arrangements of classical or jazz that make my skin crawl. You wouldn’t want to play Jimi Hendrix on the banjo, and you shouldn’t let a brass band play Wagner.

Elvis Presley. His music was largely nicked from much more talented black musicians, and his inferior versions became popular simply because he was white and (when he was young) good-looking. He wasn’t even average as a singer. During his later years he became a monument to extreme self-indulgence and dreadful Las Vegas Kitsch, a bloated laughing-stock in a sequinned jumpsuit. I like a lot of Rock’n’Roll, but Elvis was the pits.

Brahms & Liszt . Where the majestic journey of the Germanic romantic tradition veered off into a tedious cul-de-sac. Turgid and impenetrable on the one hand, flowery and overwrought on the other. But what about Brahms’ German Requiem? I’m with George Bernard Shaw, who said that it was a work to be “patiently borne only by a corpse”. When invited to hear the work for a second time, he declined. “There are are some sacrifices which should not be demanded twice from any man; and one of them is listening to Brahms’ Reqiuem.” I could have added Schumann to this too, but then I would have lost the reference to Cockney rhyming slang.

Period Instruments My heart always sinks when I pick up a CD of a much-loved piece only to read the dreaded words “played on period instruments”. Read “played on inferior instruments (and probably out of tune too)”. Why on Earth would anyone prefer the buttock-clenchingly awful scraping sound made by a baroque cello or viola da gamba to a proper instrument? And as for the so-called “natural trumpet”, words fail me.

I’ve added this from Anton, which makes the point better than I could!

periodinstruments

Barbershop Quartets Close-harmony singing can be wonderful to listen to – I’m a great admirer of Welsh male voice choirs, for example. However, the whining fake joviality of a Barbershop quartet is quite unendurable. Cut my throat with a razor rather than make me listen to one!

The Four Seasons I’m prepared to accept that Antonio Vivaldi might have written a reasonably competent piece of music in The Four Seasons. After all, he wrote so many little concerti that he’d be expected to come up with one half-decent one just by chance. The problem is that I’ve heard it so many times, in lifts, shops and, worst of all, at the other end of a telephone call centre line – and usually in very badly played versions – that I think I’ll commit murder the next time I hear it. And don’t get me started on Nigel Kennedy either.

Pan Pipes I dream of the day when it is possible to walk along a British high street without my ears being assaulted by faux Andean tootling to the accompaniment of overamplified muzak. Those guys may dress like Incas but they’ve probably never been closer to South America than Weston-super-mare. And do they think people can’t tell they’re miming?

Hector Berlioz Revoltingly overblown bombastic nonsense from a man whose ego exceeded his talent by as large a factor as you can find. My music teacher at School loved Berlioz, with the result that his vacuous splurgy ramblings were inflicted on me and my classmates lesson after lesson. The normally generous Giuseppe Verdi said that Berlioz “was a poor, sick fellow, full of fury against the world at large, bitter and spiteful.” Perhaps he couldn’t come to terms with his own mediocrity.

Folk Singers I like a lot of folk music, but don’t like English folk singers,  especially those that sing in a made-up west country accent and stick their fingers in their ears as they do so. If we have to listen to their irritating nasal droning, then at least they should have the courtesy to unblock their ears and suffer with the rest of us.

Harpsichords I could have included these under “period instruments”, but I think they deserve to be singled out for special mention. There might have been an excuse for playing a harpsichord in the days before the pianoforte was invented, but they should now all be destroyed to save us from the hideous plinky-plonky jingly-jangly noise they make. “Like two skeletons copulating on a tin roof” was how Sir Thomas Beecham described them, and who am I to disagree? Nothing was ever written for the harpsichord that didn’t sound better when played on the piano.

So there you are. That’s my list. If you feel like relieving a bit of stress feel free to add your own via the comments box. But please keep your contributions as measured and reasonable as mine.

26 Comments »

The Cold Spot

Posted in Cosmic Anomalies, The Universe and Stuff with tags , , , , on August 16, 2009 by telescoper

Musing yesterday about the rapidly approaching restart of the academic year reminded me that I really ought to get on and finish the bunch of papers sitting on my desk and on various computers. I’ve also got a book to finish before October so I’d better get cracking with that too.

More importantly, however, it reminded me to congratulate my PhD student Rockhee Sung who has just had her first paper published (in the journal Classical and Quantum Gravity). The paper is available online here and it’s free to download for a month even if you don’t have a personal or institutional subscription to the journal.

The idea of this paper came a while ago but it has taken us a long time to get everything in place to start writing it up. In the meantime other papers have been written on the subject, but Rockhee and I have done this our own way – or rather she has, as she put most of the hard work into actually doing the calculations.

About four years ago, during the course of careful statistical analysis of data from the Wilkinson Microwave Anisotropy Probe (WMAP), a group based in Santander (Spain) published a paper drawing attention to the existence of an anomalous “Cold Spot” in the data. This phenomenon has now acquired its own Wikipedia entry (here), so I won’t repeat all the details except to say that it is about 5° across and that it is colder than one would expect if the temperature fluctuations are Gaussian, as is predicted in the simplest models of the early Universe involving cosmological inflation. The spot is to the bottom right, and is marked with an arrow on the picture below.

It’s worth digressing a little here to explain that a fluctuating field of course contains both hot spots and cold spots. Because there CMB temperature fluctuations comprise a wide range of wavelengths there are also spots on different scales. Assessing the statistical significance of a single isolated feature like the cold spot is not particularly easy. Based on the brute force method of simulating skies according to the Gaussian hypothesis and then repeating the approach that led to the original discovery, the result is that around 1% of Gaussian CMB skies have a cold spot as cold as that observed in the real data. Before the non-Bayesians among you get too excited, I’ll remind you that this means that the probability of a Cold spot given the standard model is about 1%, i.e. P(Cold Spot | Standard Model)=0.01. This is NOT the same as saying that the probability of the standard model being correct is 0.01…

A probability of 1% is an in-between kind of level: not too small to be decisive, and not too large to be instantly dismissed as just being a chance fluctuation. My personal opinion is that the Cold Spot is an interesting feature that deserves to be investigated further, but is not something that in itself should cause anyone to doubt the standard model. I include it among the list of cosmological anomalies that I’ve blogged about before (for example, here, here and here). I find them interesting but don’t lose sleep worrying that the standard model is about to fall to pieces. Not yet, anyway.

Not all theorists are as level-headed as me, however, and within weeks of the discovery of the cold spot suggestions were already being put forward as to how it could be “explained” theoretically. Some of these are described in the Wikipedia entry, so I won’t rehash the list. However, one suggestion not included there was the idea that the anomalous cold spot might be there because the Universe were not isotropic, i.e. if the Cosmological Principle were violated.

Way back when I was a lad doing my own PhD, my supervisor John Barrow had been interested in globally anisotropic (but nevertheless homogeneous) cosmologies. These are models in which any observer sees different things in different directions, but the pattern seen by observers in different places is always the same. I never worked on these at the time – they seemed a bit too esoteric even for me – but I remembered bits and pieces about them from conversations.

A complete classification of all the space-times  possessing this property was completed over a hundred years ago (before General Relativity was invented) by the Italian mathematician Luigi Bianchi, and cosmological models based on them are called the Bianchi models.

This isn’t the place to go into detail about the Bianchi models: the classification is based on the mathematical properties of Lie groups, which would take me ages to explain. However, it is worth pointing out that only five Bianchi types actually contain the cosmologically principled Friedmann-Lemaître-Robertson-Walker universe as a special case: I, V, VII0 ,VIIh and IX. If you really want to know what the classes are you’ll have to look them up! Since we know our Universe is very close to being homogeneous and isotropic, it seems reasonable to look at those models capable of describing small departures from that case so the above list provides a useful subset of the models to explore.

Rockhee’s PhD project was to explore  the patterns of cosmic microwave background  fluctuations that can arise in that set of Bianchi cosmologies, not just in the temperature (which had been done before) but also in polarization (which hadn’t). I’ve already posted some of the temperature patterns Rockhee computed here.

The reason for extending wanting to extend this work to include polarization was the following. The microwave background radiation is partly linearly polarized because of the way radiation is scattered by electrons. If an electron is immersed in a radiation bath which is isotropic there is no net polarization, but if the radiation field is anisotrpic – in particular if it varies on an angular scale of 90º (i.e. a quadrupole) – then the scattered radiation will be partly polarized. In the standard cosmology the variations in the radiation field are random fluctuations so each electron “sees” a different quadupole. The net polarization field is therefore produced incoherently, by adding stochastic contributions. In  a  Bianchi model the situation is different. Each electron in this case sees the same quadupole. The polarization pattern produced is therefore coherent. Not only do anisotropic universes produce characteristic radiation patterns, they also produce a corresponding pattern in polarization.

So what does this all have to do with the Cold Spot? Well, in anisotropic spaces that are also curved, it is possible for light rays to get focussed in such a way that the entire pattern of flucuations present at least-scattering winds up concentrated in a small patch of the sky as seen by a late-time observer. for this to happen the space has to be negatively curved. Only two of the Bianchi types can do this, as there are only two that are both near-FLRW and negatively curved: V and VIIh. Both of these models could, in principle, therefore produce a cold spot by geometrical, rather than stochastic means. In the little figure below, taken from our paper, you can see examples of Bianchi VIIh (top) and Bianchi V (bottom) showing the temperature (left) and polarization (right) in each case. We’ve oriented the model to put the cold spot in approximately the right location as the observed one.

 

cold

 

The point is that there is a pretty heavy price to be paid for producing the cold spot in this way: an enormous, coherent signal in the polarized radiation field.

As often happens in such situations, somebody else had the idea to investigate these models and we were scooped to a large extent by Andrew Pontzen and Anthony Challinor from Cambridge, who recently published a paper showing that the polarization produced in these models is already excluded by experimental upper limits. They concentrated on the Bianchi VIIh case, as this appears to have a more general structure than V and it was the model first advocated as an explanation of the cold spot. In this model the combined effect of vorticity and shear introduces a swirly pattern into the radiation field that you can see clearly in the top two panels of the figure as well as focussing it into a small patch. Bianchi V doesn’t produce the same kind of pattern either in temperature or polarization: it looks more like a simple quadrupole squeezed into a small part of the sky. A particularly interesting aspect of this is that the Bianchi VIIh case clearly has a definite “handedness” while the Bianchi V one doesn’t.

The moral of all this is that the polarization of the cosmic microwave background provides key additional information that could prove decisive in eliminating (or perhaps even confirming) models of the Universe more exotic than the standard one. That’s one of the areas in which  we expect Planck to produce the goods!

In the meantime Rockhee and I will be submitting a couple of much larger papers in due course, one containing a wider discussion of the possible pattern morphologies that can be produced in these models, and another about their detailed statistical properties.

4 Comments »

Da Capo

Posted in Biographical with tags , , on August 15, 2009 by telescoper

Last week was a most momentous week, a milestone in the continuing advance of my professional career. I have tasted power. Capo di Tutti Capi!

But only for three days.

Actually it wasn’t that great. All I had to do one sign one form, with the costings for a search grant for one of our physics professors. There was nothing to it. I didn’t even have to read it, and a pen was provided too.

The point is that almost everyone was away last week and, although I was off Monday and Tuesday touring with my folks, for the latter part of the week I was designated Head of School (in the absence of the actual Head, the Deputy Head, the Director of Undergraduate Studies, and the School Manager..). I’m clearly quite a long way down the line of inheritance.

One of the reasons everyone is taking their leave now is that the A-level results are due in next week and quite a few folks will have to be back for that, to deal with next academic year’s undergraduate admissions procedures. I’m not involved directly in this process but it’s very important for the School of course.

I always think the admissions system for Universities (UCAS) is very strange. If you were going to set up a system from scratch you certainly wouldn’t have made it the way it is. Universities are given quotas of students by the government (via the funding Councils) and this is passed on to each department as a recruitment target. The departments organize interviews, open days, and all the rest of the paraphernalia of admissions practice. They then make offers to selected students in terms of A-level grades. The students, for their part, do this for several universities, getting several offers, from which they accept one as their first-choice “Firm” offer and another, usually lower, as a second-choice  “Insurance”  offer. The students then wait for their A-level results to see if they get into either of their selected departments.

Although each department has a fixed target number to recruit, it is impossible to know exactly how many will make the grades that are offered. Departments generally make more offers than they have places because some will not make the grades. However, if the success rate is higher than expected (or, as the government would put it,  if educational standards continue to rise) the department has to take too many students in. If not enough students make their grades, near- misses might be accepted but generally it’s difficult to make up a shortfall at this late stage except by going into Clearing, a pool of applicants who didn’t make it into either of their two choices.

According to today’s Guardian, the government’s recent decision to put the brakes on university expansion, combined with an increased number of applicants for university places generated by the economic recession, means that many students are unlikely to get a place at all this year.

In physics nationally there has been a substantial increase in the number of applicants over the past few years, and my own department at Cardiff University is set to meet its quota quite comfortably and is unlikely to take any students from clearing. Applications are buoyant here, at least partly because Cardiff is such an interesting place to live and offers such a vibrant social scene for students. We’re also in a special position because we get many applications from prospective students inside Wales who want to remain here to study. Cardiff University is one of only three insitutions in Wales that offer physics degrees (Aberystwyth and Swansea being the other two).

We would like to be able to increase the number of students we recruit in order to finance expansion of our staff numbers, but given the freeze on funded places from the government we would have to take quota from other departments to do so. Whether the University will allow us to do this is not at all clear, although there are departments that struggle to fill their existing quotas. Whatever happens in future years, I hope there aren’t too many disappointments in store for prospective students next week when their A-level results land on their doormat.

Anyway, the fact that we’ve reached this time of year reminds me that the start of the new academic year is not far off, and the cycle of academic life is soon to start again.  Once more, from the top!

Leave a comment »

Upon Nothing

Posted in Poetry, The Universe and Stuff with tags , , on August 15, 2009 by telescoper

I used to live in Wilmot Street in Bethnal Green, in the East End of London. I’d been resident there quite a while before I realised that the street was named after John Wilmot, Earl of Rochester, one of the great metaphysical poets, who lived from 1647 to 1680 (although I doubt he ever lived in Bethnal Green).

John Wilmot was a lifelong atheist, bon viveur and generally dissolute individual who famously converted to Christianity on his deathbed, causing much debate about whether he actually meant it.

Much of Wilmot’s literary output is actually quite crude (and often pornographic). However, first published in 1679, Upon Nothing is  certainly among the cleverest of his works and is possibly the most important poem he wrote. It’s clearly a satire  on John Milton‘s Paradise Lost (especially Book II). Starting out with a dig at the vanity of man’s attempts to solve the problem of existence, it moves into a more general lampoon of fashion victims, pompous politicians and self-important persons generally.

Updated by a few hundred years, this poem could equally be applied to the programme of quantum cosmology advocated by, e.g. Alexander Vilenkin which tries to explain the existence of the Universe by quantum tunneling  ex nihilo.  I always have a problem understanding how the equations of quantum mechanics could exist, as it were, in advance of the material they try to describe. I suppose the point is that there’s really no such thing as nothing, but then I’m no metaphysicist…

Upon Nothing

Nothing, thou elder brother even to shade,
That hadst a being ere the world was made,
And (well fixed) art alone of ending not afraid.

Ere time and place were, time and place were not,
When primitive Nothing Something straight begot,
Then all proceeded from the great united—What?

Something, the general attribute of all,
Severed from thee, its sole original,
Into thy boundless self must undistinguished fall.

Yet Something did thy mighty power command,
And from thy fruitful emptiness’s hand,
Snatched men, beasts, birds, fire, air, and land.

Matter, the wickedest offspring of thy race,
By Form assisted, flew from thy embrace,
And rebel Light obscured thy reverend dusky face.

With Form and Matter, Time and Place did join,
Body, thy foe, with these did leagues combine
To spoil thy peaceful realm, and ruin all thy line.

But turncoat Time assists the foe in vain,
And, bribed by thee, assists thy short-lived reign,
And to thy hungry womb drives back thy slaves again.

Though mysteries are barred from laic eyes,
And the Divine alone with warrant pries
Into thy bosom, where thy truth in private lies,

Yet this of thee the wise may freely say,
Thou from the virtuous nothing takest away,
And to be part of thee the wicked wisely pray.

Great Negative, how vainly would the wise
Inquire, define, distinguish, teach, devise?
Didst thou not stand to point their dull philosophies.

Is, or is not, the two great ends of Fate,
And true or false, the subject of debate,
That perfects, or destroys, the vast designs of Fate,

When they have racked the politician’s breast,
Within thy bosom most securely rest,
And, when reduced to thee, are least unsafe and best.

But Nothing, why does Something still permit
That sacred monarchs should at council sit
With persons highly thought at best for nothing fit?

Whist weighty Something modestly abstains
From princes’ coffers, and from statesmen’s brains,
And Nothing there like stately Nothing reigns,

Nothing, who dwellest with fools in grave disguise,
For whom they reverend shapes and forms devise,
Lawn sleeves, and furs, and gowns, when they like thee look wise.

French truth, Dutch prowess, British policy,
Hibernian learning, Scotch civility,
Spaniard’s dispatch, Dane’s wit are mainly seen in thee.

The great man’s gratitude to his best friend,
King’s promises, whore’s vows, towards thee they bend,
Flow swiftly to thee, and in thee never end.

Incidentally, the first use of the word metaphysical to describe the particular “poetic style, characterized by wit, syntactic complexity, and the use of elaborate and intricate schemes of imagery to express abstract ideas and emotional states” was in 1693, by John Dryden who clearly meant it to be pejorative. Those whose philosophical inclination is in the direction of positivism would look down on the more orthodox meaning of the word metaphysical, i.e. meaning “of or relating to the  branch of philosophy that deals with the first principles of things or reality, including questions about being, substance, time and space, causation, change, and identity”. Dryden, however, was alluding to another meaning, now quite rare but prevalent in the 17th Century, that has something to do with magical or supernatural things beyond the bounds of respectable thought. Thomas More used the word “metaphysical” to attack William Tyndale for translating the Bible into English, for example.

You can find other examples of  metaphysical poetry in the collection I blogged about here.

7 Comments »

Along the bent and Devon-facing seashore

Posted in Biographical with tags , , , , on August 14, 2009 by telescoper

I’ve been off for a few days because my folks have been visiting from Newcastle. The good weather (on Tuesday, at least) gave us the opportunity to go for a drive around the Gower peninsula to the west of Swansea, seeing  some of the sights. I don’t think I’m very good at travelogues, but here are a few memories of the trip.

Along the north coast first: Penclawdd, Crofty and Llanrhidian. Weobley Castle stands decaying and forlorn, overlooking a salt marsh grazed by sheep and horses. In the distance, over the estuary, a nondescript town. Through binoculars I see they’re building a new Asda. What was there 700 years ago when they built the Castle?

Rossili Bay, at the western end of the peninsula. Beaches and dunes under cliffs. Caravans as far as the eye can see. Impatient surfers waiting in wet-suits for the tide to come in. Don’t they check the tide tables? The smell of Fish and Chips fails to lure us.

We drive south. White cottages shining bright in the sunshine, then down steep hills into cool dark tunnels formed by trees either side of the narrow roads, their leaves meeting overhead. I wonder what it’s like down here when it’s raining: the road must turn into a torrent. Then up on top again. Bright sunshine, a small airport and more caravans.

Driving south we come again to the jagged coast and see  Devon  along the horizon in front of us. I’m surprised it is so clear, as it must be at least 30 miles away. It’s dark and solid, a featureless granite wall. It reminds me of Dylan Thomas Reminiscences of Childhood ..

There was another world where with my friends I used to dawdle on half holidays along the bent and Devon-facing seashore…

I had always thought he just knew that Devon was there, not that he had actually seen it. I decide I like the word “dawdle”.

Port Eynon, at the southernmost tip of the Gower. A small beach between two headlands with a larger beach to one side. Fish and Chips and hot tea offer themselves. This time we accept. Inside the café (“The Captain’s Table”) an old newspaper in a frame on the wall tells stories of smuggling and wreck sales. Another, dated 1916, says that three lifeboat men had drowned while trying to rescue a ship that had foundered off the headland where the derelict oyster pans lie.

The sand dunes behind the beach are covered in wild flowers and they are covered in turn with vividly coloured beetles and butterflies. The tide is still out and it’s too far to walk over the rocks to get to the sea to have a paddle.  It’s not difficult to imagine a boat coming to grief in this place. There are flags all over warning about the dangers of the current. It must be a desolate place in the winter.

I think about retirement.

We pass a church with a memorial to the brave men who lost their lives that day in 1916. The lifeboat station was moved in 1919 because the place was too dangerous. Stopping to read the inscription, I’m almost run over on the narrow road by a big van carrying surfers and their gear. I wonder why they’re in such a hurry when the tide is out.

We try to avoid getting snarled up in traffic in Swansea on the way home. We fail.

As an afterthought, we head for The Mumbles, park the car and walk. Ambling along the curved promenade in the evening sunshine, a large and lumpy lady waddles towards us with sweat running down  pale pink arms;  her voluminous black dress conceals a hefty bosom that makes me think of two sacks of Tyne coal. It turns out The Mumbles is named after the French Mamelles – meaning breasts – although it takes its name from the shape of two small islands off Mumbles Head rather than from some distant ancestor of the lady I’ve just seen.

The long promenade sweeps along the side of Swansea bay to the pier and a lighthouse. The tide is still out. It seems miles to the sea, over nasty rocks that look like cinder. No beach. On the esplanade dozens of boats lie stranded, like befuddled whales that have run aground to their doom.

Dogs carry sticks and people carry ice-creams.

It’s evening now and I wonder why the tide seems to have been out everywhere we’ve been since morning.

On the inland side of the Mumbles there is a hotch-potch of closed-down pubs  and up-market bistros, next door to one another, an amusement hall and, next to it, tennis courts. The inevitable Fish and Chips. Nearer the pier  there’s an open-air Café called Verdi’s. It’s packed and doing a roaring trade in ice-creams. The waiters are very handsome but I’m not convinced they are Italian. A man sings “Just one Cornetto” and laughs loudly, but nobody else does.

Back to the car, through the centre of Swansea, and then home in less than an hour. Pimms and Lemonade in the garden before going to the pub for dinner.

Leave a comment »

« Older Entries
Newer Entries »