Archive for July, 2015

Exciting Opportunity in Experimental Physics at the University of Sussex!

Posted in Education, The Universe and Stuff with tags , , , , on July 23, 2015 by telescoper

Just a quick update on the news that Department of Physics & Astronomy at the University of Sussex has an exciting opportunity in the form of a brand new Chair position in Experimental Physics. The advertisement appeared on the University of Sussex website somedays ago. But it has now appeared on Nature Jobs and the Times Higher websites. It is also in today’s print edition of the Times Higher. At least I think it is. I couldn’t find a copy in W.H. Smith’s when I went there today. Obviously it has sold out because word has got out about this job!

I’m taking the liberty of reposting a description of the new position here, but for fuller details please visit the formal advertisement.

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The School of Mathematical and Physical Sciences seeks to appoint a Professor in Experimental Physics in the Department of Physics & Astronomy to lead the next phase of expansion and diversification of the research portfolio within the School by establishing an entirely new research activity in laboratory-based physics.

Sufficient resources will be made available to the selected candidate to establish a new group at Sussex in their field of experimental physics including, for example, condensed matter (interpreted widely), materials science, nanophysics or biophysics. Applicants in research areas with scope for interdisciplinary collaborations with other Schools at the University of Sussex (e.g. Life Sciences, Engineering & Informatics or Brighton and Sussex Medical School) are encouraged, especially  those in areas with potential for generating research impact, as defined in the context of the UK Research Excellence Framework.

The successful applicant will have a proven track-record of success in obtaining substantial external funding through research grants and/or industrial sponsorship.

The appointee will be supported with substantial (seven-figure) sum for start-up funding and an extensive newly-refurbished laboratory space. The financial package on offer will also support the appointment of at least two further experimental lectureships; the appointed professor is expected to be strongly involved in recruitment to these positions.

Informal (and confidential) enquiries may be addressed in the first instance to the Head of School, Professor Peter Coles (P.Coles@sussex.ac.uk).

The Curious Case of the 3.5 keV “Line” in Cluster Spectra

Posted in Bad Statistics, The Universe and Stuff with tags , , , , , , on July 22, 2015 by telescoper

Earlier this week I went to a seminar. That’s a rare enough event these days given all the other things I have to do. The talk concerned was by Katie Mack, who was visiting the Astronomy Centre and it contained a nice review of the general situation regarding the constraints on astrophysical dark matter from direct and indirect detection experiments. I’m not an expert on experiments – I’m banned from most laboratories on safety grounds – so it was nice to get a review from someone who knows what they’re talking about.

One of the pieces of evidence discussed in the talk was something I’ve never really looked at in detail myself, namely the claimed evidence of an  emission “line” in the spectrum of X-rays emitted by the hot gas in galaxy clusters. I put the word “line” in inverted commas for reasons which will soon become obvious. The primary reference for the claim is a paper by Bulbul et al which is, of course, freely available on the arXiv.

The key graph from that paper is this:

XMMspectrum

The claimed feature – it stretches the imagination considerably to call it a “line” – is shown in red. No, I’m not particularly impressed either, but this is what passes for high-quality data in X-ray astronomy!

There’s a nice review of this from about a year ago here which says this feature

 is very significant, at 4-5 astrophysical sigma.

I’m not sure how to convert astrophysical sigma into actual sigma, but then I don’t really like sigma anyway. A proper Bayesian model comparison is really needed here. If it is a real feature then a plausible explanation is that it is produced by the decay of some sort of dark matter particle in a manner that involves the radiation of an energetic photon. An example is the decay of a massive sterile neutrino – a hypothetical particle that does not participate in weak interactions –  into a lighter standard model neutrino and a photon, as discussed here. In this scenario the parent particle would have a mass of about 7keV so that the resulting photon has an energy of half that. Such a particle would constitute warm dark matter.

On the other hand, that all depends on you being convinced that there is anything there at all other than a combination of noise and systematics. I urge you to read the paper and decide. Then perhaps you can try to persuade me, because I’m not at all sure. The X-ray spectrum of hot gas does have a number of known emission features in it that needed to be subtracted before any anomalous emission can be isolated. I will remark however that there is a known recombination line of Argon that lies at 3.6 keV, and you have to be convinced that this has been subtracted correctly if the red bump is to be interpreted as something extra. Also note that all the spectra that show this feature are obtained using the same instrument – on the XMM/Newton spacecraft which makes it harder to eliminate the possibility that it is an instrumental artefact.

I’d be interested in comments from X-ray folk about how confident we should be that the 3.5 keV “anomaly” is real…

Software Use in Astronomy

Posted in Education, The Universe and Stuff with tags , , , , on July 21, 2015 by telescoper

I just saw an interesting paper which hit the arXiv last week and thought I would share it here. It’s called Software Use in Astronomy: An Informal Survey and the abstract is here:

softwareA couple of things are worth remarking upon. One concerns Python. Although I’m not surprised that Python is Top of the Pops amongst astronomers – like many Physics & Astronomy departments we actually teach it to undergraduates here at the University of Sussex – it is notable that its popularity is a relatively recent phenomenon and it’s quite impressive how rapidly it has caught on.

Another interesting thingis the continuing quite heavy use of Fortran. Most computer scientists would consider this to be an obsolete language, and is presumably mainly used because of inertia: some important and well established codes are written in it and presumably it’s too much effort to rewrite them from scratch in something more modern. I would have thought that Fortran would have been used primarily by older academics, i.e. old dogs who can’t learn new programming tricks. However, that doesn’t really seem to be the case based on the last sentence of the abstract.

Finally, it’s quite surprising that over 40% of astronomers claim to have had no training in software development. We do try to embed that particular skill in graduate programmes nowadays, but it seems that doesn’t always work!

Anyway, do read the paper yourself. It’s very interesting. Any further comments through the box below please, but please ensure they compile before submitting them…

 

The England Cricket Team – An Apology

Posted in Cricket with tags , on July 21, 2015 by telescoper

Some days ago I wrote a post on this blog about the 1st Ashes Test between England and Australia at Cardiff which resulted in an England victory. In that piece I celebrated the team spirit of England’s cricketers and some memorable performances with both bat and ball. I also suggested that England had a realistic prospect of regaining the Ashes.

However, in the light of Australia’s comprehensive victory in the 2nd Ashes Test at Lord’s during which the England bowlers were ineffectual, their batsmen inept and the team spirit non-existent, I now realize that my earlier post was misleading and that they actually have absolutely no chance of regaining the Ashes. I apologize for any inconvenience caused by my ealier error.

I hope this clarifies the situation.

P.S. Kevin Pietersen is 35.

Raincheck

Posted in Jazz with tags , , , , on July 20, 2015 by telescoper

Well, the British Summer has arrived at last. It’s raining. The weather reminded me of little number I posted some time ago by Tommy Flanagan, one of the most consistently enjoyable but underrated Jazz pianists of all time. So naturally I decided to post it again. Tommy Flanagan (who died in 2001) was probably best known as the long-time accompanist of Ella Fitzgerald but he also played on a number of really important Jazz albums with Sonny Rollins and John Coltrane, to name just two. He also loved to play within the classic Jazz piano trio format with George Mraz (bass) and Kenny Washington (drums). Here they are playing a nice tune by the great Billy Strayhorn, called Raincheck

Astronomy: One of the Seven Liberal Arts

Posted in Art, Education, History, The Universe and Stuff with tags , , , on July 20, 2015 by telescoper

This morning I came across this picture (via @hist_astro on Twitter):

Seven Liberal ArtsIt is by Giovanni dal Ponte and was painted in or around 1435; the original is in the Museo Nacional del Prado in Madrid. It depicts the Seven Liberal Arts which, in antiquity were considered the essential elements of the education system. The Arts concerned are: Grammar, Rhetoric, Dialectic, Astronomy, Arithmetic, Geometry and Music. Appropriately enough, Astronomy is in the middle.

I suspect some of you may have noticed that there are more than seven figures in the painting. That’s because each of the Liberal Arts is itself represented by a (female) figure, presumably a Goddess, and also a famous character associated with the particular discipline. Second from the right, for example, you can see Arithmetic accompanied by Pythagoras, who seems to be trying to copy from her notebook. Astronomy. In the centre, kneeling at the feet of Urania (the muse of Astronomy) is Ptolemy..

It’s quite interesting to look at the structure of a Liberal Arts education as it would be in classical antiquity. The first three subjects (Grammar, Rhetoric and Dialectics) formed the Trivium (from which we get the English word “trivial”). “Grammar” means the science of the correct usage of language, knowledge and understanding of which helps a person to speak and write correctly; “Dialectic” basically means “logic”, the science of rational thinking as a means of arriving at the truth; and “Rhetoric” the science of expression, especially persuasion, which includes ways of organizing and presenting an argument so that people will understand and hopefully believe it. These may have been considered trivial in ancient times, but I can’t help thinking that we could do with a lot more emphasis on such fundamental skills in the modern curriculum.

After the Trivium came the Quadrivium: Arithmetic, Geometry, Astronomy and Music all of which were considered to be disciplines connected with Mathematics. Presumably these are the non-trivial subjects. We might nowadays consider Astronomy to be a mathematical subject – indeed in the United Kingdom astronomy was until relatively recently generally taught in mathematics departments, even after the rise of astrophysics in the 19th Century. On the other hand, fewer would nowadays would recognize music as being essentially mathematical in nature. Historically, however the connections between music, mathematics and natural philosophy were many and profound.

Of course there are now many other disciplines and it would be impossible for any education to encompass all fields of study, but I do think that it’s a shame that modern education systems are so lacking in breadth, as they tend to emphasize the differences between subjects rather than what they all have in common.

Gowns, Grammar and Graduation

Posted in Biographical with tags , on July 19, 2015 by telescoper

After yesterday’s post about the fascinating story of the recipient of an honorary degree, I thought I’d add a few personal comments about last week’s graduation ceremony for the School of Mathematical and Physical Sciences at the University of Sussex, at which I had the pleasure of presenting the graduands. Graduation ceremonies are funny things. With all their costumes and weird traditions, they do seem a bit absurd. On the other hand, even in these modern times, we live with all kinds of  rituals and I don’t see why we shouldn’t celebrate academic achievement in this way. I love graduation ceremonies, actually. As the graduands go across the stage you realize that every one of them has a unique story to tell and a whole universe of possibilities in front of them. How their lives will unfold no-one can tell, but it’s a privilege to be there for one important milestone on their journey. Getting to read their names out is quite stressful – it may not seem like it, but I do spend quite a lot of time fretting about the correct pronunciation of the names.  It’s also a bit strange in some cases finally to put a name to a face that I’ve seen around the place regularly, just before they leave the University for good.

Anyway, here are the obligatory “mortar boards in the air” pictures of graduates and academic staff from  Physics & Astronomy and Mathematics, respectively, taken just outside the Brighton Dome shortly after the ceremony. I am actually in both of these pictures. Somewhere. I also got hit on the head twice by descending hats.

Hatshats_2

Graduation is a grammatical phenomenon too. The word “graduation” is derived from the latin word gradus meaning a step, from which was eventually made the mediaeval latin verb graduare, meaning “to take a degree”. The past participle  of this is formed via the supine graduatus, hence the English noun “graduate” (i.e. one who has taken a degree). The word graduand, on the other hand, which is used before and during the ceremony to describe those about to graduate, is from the  gerundive form graduandus meaning “to be graduated”. What really happens grammatically speaking, therefore, is that students swap their gerundives for participles, although I suspect most participants don’t think of it in quite those terms.

Graduation ceremonies are quite colourful because staff wear the gown appropriate to their highest degree. Colours and styles vary greatly from one University to another even within the United Kingdom, and there are even more variations on show when schools contain staff who got their degrees abroad. Since I got my doctorate from the University of Sussex, which was created in the 1960s, the academic garb I used to wear on these occasions  is actually quite modern-looking. With its raised collar, red ribbons and capped shoulders it’s also more than a little bit camp. It often brought  a few comments when I participated in the academic procession prior to graduation, but I usually replied by saying I bought the outfit at Ann Summers. Here is a picture of me wearing the old-style Sussex doctoral gown just after I received my DPhil in 1989 at a ceremony at the Brighton Centre:

Graduation

Unfortunately the University decided to change the style recently to something a bit more standard, as demonstrated in this picture from yesterday’s post:

John Francis receiving his Honorary Doctorate from the Chancellor, Sanjeev Bhaskar.

John Francis receiving his Honorary Doctorate from the Chancellor, Sanjeev Bhaskar.

That’s me on the far left, in case you didn’t realise. I still feel a bit uncomfortable wearing academic dress that’s different from what I wore for my graduation. I did mention this once to the Vice Chancellor and he said that it would be perfectly alright if I wore the old style instead. The problem is that I never actually bought the gown and Ede & Ravescroft, who supply the gear for such occasions, no longer provide it. Perhaps I should try to find a second-hand one somewhere?

Graduation of course isn’t just about dressing up. Nor is it only about recognising academic achievement. It’s also a rite of passage on the way to adulthood and independence, so the presence of the parents at the ceremony adds another emotional dimension to the goings-on. Although everyone is rightly proud of the achievement – either their own in the case of the graduands or that of others in the case of the guests – there’s also a bit of sadness to go with the goodbyes. It always seems that as a lecturer you are only just getting to know students by the time they graduate, but that’s enough to miss them when they go.

I’ve also been through two graduations on the other side of the fence, as it were. My first degree came from Cambridge so I had to participate in the even more archaic ceremony for that institution. The whole thing is done in Latin there (or was when I graduated) and involves each graduand holding a finger held out by their College’s Praelector and then kneeling down in front of the presiding dignitary, who is either the Vice-Chancellor ot the Chancellor. I can’t remember which. It’s also worth mentioning that although I did Natural Sciences (specialising in Theoretical Physics), the degree I got was Bachelor of Arts. Other than that, and the fact that the graduands walk to the Senate House from their College through the streets of Cambridge,  I don’t remember much about the actual ceremony.

I was very nervous for that first graduation. The reason was that my parents had divorced some years before and my Mum had re-married. My Dad wouldn’t speak to her or her second husband. Immediately after the ceremony there was a garden party at my college, Magdalene, at which the two parts of my family occupied positions at opposite corners of the lawn and I scuttled between them trying to keep everyone happy. It was like that for the rest of the day and I have to say it was very stressful. A few years later I got my doctorate (actually DPhil) from the University of Sussex, at the Brighton Centre on the seafront. It was pretty much the same deal again with the warring family factions, but I enjoyed the whole day a lot more that time. And I got to wear the funny gown.

Anyway, apologies for going all biographical. My main purpose for writing this post was to thank Thursday’s graduands graduates for the many kind comments and to offer my heartiest congratulations to those I didn’t get to talk to in person. If you are a recent graduate from the School of Mathematical and Physical Sciences then please do stay in touch and let us know how you get on in the big wide world!

Honoris Causa: John Francis, Inventor of the QR Algorithm

Posted in The Universe and Stuff with tags , , , , , , on July 18, 2015 by telescoper

It’s been yet another busy week, trying to catch up on things I missed last week as well as preparing for Thursday’s graduation ceremony for students from the School of Mathematical and Physical Sciences. At this year’s ceremony, as well as reading out the names of graduands from the School of which I am Head, I also had the pleasant duty of presenting mathematician John G.F. Francis for an Honorary Doctorate of Science.

The story of John Francis is a remarkable one which I hope you will agree if you read the following brief account which is adapted from the oration I delivered at the ceremony. It was a special pleasure to asked to present this award because you could never wish to meet a more modest or self-effacing individual. Indeed, when I asked him at the lunch following the ceremony, what he thought of the work for which he had been awarded a degree honoris causa he shrugged it off, and said that he thought it was an obvious thing to do and anyone else could have done it had they thought of it. Maybe that’s true in hindsight, but the point is that “they” didn’t and “he” did. The fact that it has taken over fifty years for him to be recognized for something so important is regrettable to say the least, but I am glad to have been there to see him justifiably honoured. Great thanks are due to Drs Omar Lakkis and Anotida Madzvamuse of the Department of Mathematics at the University of Sussex for bringing his case to the attention of the University as eminently suitable for such an honour. So impressed were the graduating students that a number shook his hand as they passed him on the stage during their own part of the ceremony. I’ve never seen that happen before!

John Francis receiving his Honorary Doctorate from the Chancellor, Sanjeev Bhaskar.

John Francis receiving his Honorary Doctorate from the Chancellor, Sanjeev Bhaskar.

John Francis is a pioneer in the field of mathematical computation where his name is more-or-less synonymous with the so-called “QR algorithm”, an ingenious factorization procedure used to calculate the eigenvalues and eigenvectors of linear operators (represented as matrices).

Before I go on it’s probably worth explaining that the letters ‘QR’ don’t stand for any words in particular. The algorithm involves decomposing the matrix whose eigenvalues are required into the product of an orthogonal matrix (which Francis happened to call Q) and an upper-triangular matrix (which Francis happened to call R). In fact in his original manuscript, the orthogonal matrix was called O but it was subsequently changed to avoid confusion with ‘O’. At any rate, certainly has nothing to do with research funding!

The mathematics and physics graduates in the audience were probably well aware of the importance of eigenvalue problems, which crop up in a huge variety of contexts in these and other scientific disciplines, from geometry to graph theory to quantum mechanics to geology to molecular structure to statistics to engineering; the list is almost endless. Indeed here can be few people working in such fields who haven’t at one time or another turned to the QR algorithm in the course of their calculations. I know I have, in my own field of astrophysics! It has become a standard component of any theoretician’s mathematical toolkit because of its numerical stability.

The algorithm was first derived by John Francis in two papers published in 1959 and, independently a couple of years later, by the Russian mathematician Vera Kublanovskaya (who passed away in 2012). You can find both the papers online: here and here. Interestingly, the problem that John Francis was trying to solve when he devised the QR algorithm concerned the “flutter” or vibrations of aircraft wings.

But it is in the world of the World Wide Web that the QR algorithm has had perhaps its greatest impact. Many of us who were using the internet in 1998 were astonished when Google arrived on the scene because it was so much faster and more effective than all the other search engines available at the time. The secret of this success was the PageRank algorithm (named after Larry Page, one of the founders of Google) which involved applying the QR decomposition to calculate numerical factors expressing the relative “importance” of elements within a linked set (such as pages on the World Wide Web) measured by the nature of their links to other elements. The QR algorithm is not the only technique exploited by Google, but it is safe to say that it is what gave Google its edge.

The achievements of John Francis are indeed impressive, even more so when you read his biography, for he did all this pioneering work in numerical analysis without even having an undergraduate degree in Mathematics.

John Francis actually left school in 1952 and obtained a place at Christ’s College, Cambridge for entry in 1955, after two years of National Service during which he served in Germany and Korea with the Royal Artillery. On leaving the army in 1954 he worked for a time at the National Research Development Corporation which was set up in 1948 by the Attlee government in order to facilitate the transfer of new technologies developed during World War 2 into the private sector in an effort to boost British commerce and industry. Among the priority areas covered by the NRDC was computing, and it was there that John Francis cut his teeth in the field of numerical analysis. He went to University as planned but did not complete his degree, instead returning to the NRDC in 1956 after less than a year of study. It was while working there in 1958 and 1959 that he devised the QR algorithm.

He left the NRDC in 1961 to work at Ferranti Ltd after which, in 1967, he moved to Brighton and took up a position at the University of Sussex in the Laboratory of Experimental Psychology, helping to devise a new computer language for running experiments. He left the University in 1972 to work in various private sector computer service companies in Sussex. He has now retired but still lives locally, in Hove.

Having left the field of numerical analysis in the 1960s, John Francis had absolutely no idea of the impact his work on the QR algorithm had had, nor was he aware that it was widely recognized as one of the Top Ten Algorithms of the Twentieth Century, until he was traced and contacted in 2007 by the organizers of a mini-symposium that was being planned to celebrate 50 years of the QR algorithm; he was the opening speaker at that meeting in Glasgow when it took place in 2009.

More recently still, in 2011, after what he describes as “sporadic” study over many years, John Francis was awarded an undergraduate degree from the Open University, 56 years after he started one at Cambridge.  I am very glad that there was no similar delay in him proceeding to a Doctorate!

Physics is more than applied mathematics

Posted in Education, The Universe and Stuff with tags , , , on July 15, 2015 by telescoper

I thought rather hard before reblogging this, as I do not wish to cause any conflict between the different parts of my School – the Department of Mathematics and the Department of Physics and Astronomy!

I don’t think I really agree that Physics is “more” than Applied Mathematics, or at least I would put it rather differently. Physics and Mathematics intersect, but there are parts of mathematics that are not physical and parts of physics that are not mathematical.

Discuss.

Protons for Breakfast

A problem set for potential applicants in the foyer of the Cavendish Laboratory. Despite appearances - this is not physics! A problem set for potential applicants in the foyer of the Physics department of a premier UK university. It looks like physics, but it is in fact maths. The reason is that in the context of this problem, the string cannot pull a particle along at all unless it stretches slightly. Click the image for a larger diagram.

While accompanying my son on an Open Day in the Physics Department of a premier UK university, I was surprised and appalled to be told that Physics ‘was applied mathematics‘.

I would just like to state here for the record that Physics is notapplied mathematics.

So what’s the difference exactly?

I think there are two linked, but subtly distinct, differences.

1. Physics is a science and mathematics is not.

This means that physics has an experimental aspect. In physics, it is possible to disprove a hypothesis by experiment: this cannot be done in maths.

2. Physics is about…

View original post 256 more words

An Exciting Opportunity in Experimental Physics at the University of Sussex!

Posted in Education, The Universe and Stuff with tags , , , , on July 14, 2015 by telescoper

After much planning and preparatory work, I’m pleased that I am now in a position to announce that the Department of Physics & Astronomy at the University of Sussex has an exciting opportunity in the form of a brand new Chair position in Experimental Physics. The advertisement will shortly appear in both Nature and the Times Higher but it has already appeared on the University of Sussex website. I’m taking the liberty of posting a description of the new position here, but for fuller details please visit the formal advertisement.

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The School of Mathematical and Physical Sciences seeks to appoint a Professor in Experimental Physics in the Department of Physics & Astronomy to lead the next phase of expansion and diversification of the research portfolio within the School by establishing an entirely new research activity in laboratory-based physics.

Sufficient resources will be made available to the selected candidate to establish a new group at Sussex in their field of experimental physics including, for example, condensed matter (interpreted widely), materials science, nanophysics or biophysics. Applicants in research areas with scope for interdisciplinary collaborations with other Schools at the University of Sussex (e.g. Life Sciences, Engineering & Informatics or Brighton and Sussex Medical School) are encouraged, especially  those in areas with potential for generating research impact, as defined in the context of the UK Research Excellence Framework.

The successful applicant will have a proven track-record of success in obtaining substantial external funding through research grants and/or industrial sponsorship.

The appointee will be supported with substantial (seven-figure) sum for start-up funding and an extensive newly-refurbished laboratory space. The financial package on offer will also support the appointment of at least two further experimental lectureships; the appointed professor is expected to be strongly involved in recruitment to these positions.

Informal (and confidential) enquiries may be addressed in the first instance to the Head of School, Professor Peter Coles (P.Coles@sussex.ac.uk).