Monday, 19 October 2020

Open Access Royal Society (one week only)

While we wait for all academic publishing to be properly open access, Royal Society Publishing have kindly opened up their pretty extensive archive for free for the next week.  See here

They do not have an extensive amount of nuclear physics stuff, but they are currently my publishing BFF because they published my student's article on Terrell rotations earlier this year, whcih I may have metioned here beforeMore than once. In fact, more than twice.  Well, modesty prohibits me from linking to the paper again, but that's okay because there are lots of other articles of interest, dating back, of course, many centuties.  

If anyone has any favourite articles from Proceedings of the Royal Society, or the Philosophical Transactions, please do share in the comments. 

Here's a snapshot of some sketches by William Herschel, from Philosophical Transactions, vol 74, p233 (1784)


Tuesday, 6 October 2020

Lattice calculations of nuclear vibrations

  I just received a notification that the penultimate article in the special topic in Frontiers In Physics that I am co-editing has appeared.  It's called "Nuclear Collective Dynamics in Transport Model with the Lattice Hamiltonian Method" and it deals with a method in which the motion of a nucleus is described in terms of the the evolution of the Wigner function (the nuclear density Fourier-transformed to the momentum representation).  By including collisions between nucleons in the formalism, the authors describe the width of giant resonances rather well, as shown in the picture above (fig 7 from the paper).

 That leaves just one more paper to appear, and also means that I should get on with writing the editorial in time to make a free e-book of the Special Topic.

Roger Penrose, Nobel Laureate 2020

Roger Penrose was announced this morning as the winner of half of the 2020 Nobel Prize in Physics, with the other half being shared equally between Andrea Ghez and Reinhard Genzel.  I will leave others to explain about the physics behind the prize award, since it is not really my area of expertise, but I wanted to post to mention the ways Penrose and his work has cropped up in my life

As a physics-interested schoolboy, I used to read through popular science books.  Probably the first one I read, to the best of my memory, was Stephen Hawking's A Brief History of Time, which I got for Christmas the year it came out and was something of a must-read book for more or less anyone, though there was a kind of joke that few people finished it.  I did finish it, and though I probably didn't understand it all, I found it at least readable and understood the words and got a sense always of the ideas being communicated, even if perhaps I didn't always gain a deep understanding. 

Another one I read, while I was in the lower sixth (what we used to call Year 12) and applying to University, was Penrose's The Emperor's New Mind.  I lent my copy to a girl I fancied and never got it back.  I later learned that the rule of lending books to anyone was that you just go out and buy yourself another copy straight away.  Anyway, I had finished the book, though I'm not sure I can remember too much of it in great detail now.  It did make quite an impression on me at the time, though I think it was "harder" than Stephen Hawking's book and no doubt there was lots I didn't understand.  I liked it for its broad sweep, combining ideas from physics to advanced mathematics, Turing machines, and on to somewhat more speculative stuff (which I didn't distinguish at the time, I suppose) to do with consciousness.  

In December of 1991, when I was in the lower sixth and up in Oxford for an interview to read Physics and Philosophy I noticed that Penrose was giving a lecture for prospective students in Mathematics.  In my interview for my place in college when asked if I had any questions I said I'd seen the advert for the talk and I asked if it would be okay if I went along to it.  I'm not sure what they thought of my question - I guess I had no idea at the time that it would be perfectly fine for anyone to turn up and they wouldn't exactly be checking to see if I was really a prospective mathematics student.  Anyway, I went along, and enjoyed the talk very much.  Penrose talked about the famous Penrose tiles.  I remember particularly a demonstration of how for certain near-symmetries you could make the symmetry almost perfect - as near to perfect as you liked, except not quite actual perfection - and he showed this by having two identical overhead projector slides with a 5-fold Penrose tiling, which he overlaid, and you could see the bands made in the thin regions where the pattern didn't quite repeat.  

I don't think I have seen Penrose in person since then, 29 years ago, but I did get a copy of his huge "The Road To Reality" book as a 30th birthday present a bit later (in 2004).  That's been sitting on my office shelves unread, I have to admit.  I'm sure, as a practicing theoretical physicist, that I ought to be able to read and understand it, but even to me, opening it up it does look intimidating.

The other Penrose anecdote I have is that I found out at some point (perhaps the advent of wikipedia) that I share a birthday with several famous physicists, two of whom won Nobel prizes long ago).  Now I can fill in another cell in this table:

PhysicistDate of BirthYear of Nobel Prize
E.O. Lawrence08/08/1901 1939
P.A.M. Dirac08/08/1902 1933
R. Penrose08/08/1931 2020
P. D. Stevenson (me!)

The final Penrose-related thing links with my research:  Earlier this year I co-published a paper with a bachelor's student based on his Final Year Project on the visual appearance of objects moving very fast (at an appreciable fraction of the speed of light).  This is a new look at something which are either called  Terrell Rotations, after the author who first got his name attached to it, or as the Penrose-Terrell effect, since Penrose independently submitted a paper on the same topic, published in the same year as Terrell.  Even more properly, it can be called the Lampa-Terrell-Penrose effect, since Lampa published it first, in a paper that wasn't so widely known.

Here's a picture of Penrose, which he sent to the Nobel Committee from his house in Oxford this morning

Wednesday, 23 September 2020

Science books of the year

 I saw yesterday that the Royal Society published their shortlist for their science books of the year.  There are 6 in the shortlist: The World According to Physics by Jim Al-Khalili, The Body by Bill Bryson, The Great Pretender by Susannah Cahalan, Explaining Humans by Camilla Peng, The Double X Economy by Linda Scott, and Transcendence by Gaia Vince.

Unusually, since I don't read a lot of popular science, I've actually read two of the books:  Transcendence and The World According to Physics.  They are both excellent, and would be worthy winners.  I got Transcendence for Christmas last year, and found its arguments compelling that humans' achievements are part and parcel of the way humans work together; the network of ideas, activities, language and culture evolve together with biological humans and have created a kind of super-organism.  Mind-blowing, well-researched and full of interesting anecdotes, I found myself wanting to tell people things I'd read in it as I was going through.  

The World According to Physics is right up my own subject area, so though I would expect to enjoy it, I wouldn't necesasrily prioritise adding a popular explanation of something I think I know well to my reading list, but I'm glad I did read it:  Sure, I knew most of the stuff already, but it was infused with such a joy for the wonder of the Universe, and our way of explaining it through physics, that I rekindled my own sense of awe at what I sometimes let lapse as part of my day-to-day activities.  I did even learn a few things, thanks to the inclusion of lots of very up-to-date and speculative ideas (which were flagged as such).  I should add that I read a draft of the book and gave some comments, and the author did hand me a copy once it was published.  Jim is my colleague at the Unviersity of Surrey.  No payment was received for this review ;-)

Wednesday, 16 September 2020


 The document format pdf is pretty good when you want to make nice-looking output for printing for your scientific paper.  It's not always so handy when you want to read something on e.g. your phone screen, though, where you have to do a combination of zooming in and scrolling around to be able to read a paper.

A nicely-formated html version of a scientific paper, on the other hand, should be able to render nicely on a wider range of screens, and these days reading from screen has largely superseded reading from paper for me.  I read on Twitter about an arxiv-to-html translator called arxiv-vanity.  You give it an arxiv URL and it returns a nice readble web-page version of the paper you are interested in.  

I tried it on the recent whitepaper / review I was involved in writing on fission theory and the results are impressive.  Perhaps arxiv will fold it into its own offering soon.  

Friday, 11 September 2020

Update on the time-dependent methods special topic

 I last posted an update back in June about the Special Topic in Frontiers in Physics that I am co-editing.   Then, a new article on solitons in nuclear reactions had just been published.  This was actually followed a few days later with another paper, and then there has been a fallow period while the last few papers go through refereing, proofing, and publication.  Today, the next of those was published. so let me briefly mention the two new papers since June:

Marc Verriere and David Regnier have written a review on the time-dependent Generator Coordinate Method.  In fact, they discuss a number of related models which all share the character of mixing multiple Slater determinant wave functions to represent complex nuclear phenomena (reactions, fission) in which there is a significan change over time of the quantum state, and for which a time-dependent method is appropriate.  It's a nice contribution the Special Topic, covering one of the current hot methods in nuclear theory.  I can say this since I have a PhD student working on something that can be termed time-dependent Generator Coordinate Method, though it is not quite the same as the methods presented by Verriere and Regnier.  

 The other paper, published today, is written by a University of Surrey undergradute student who took a year-long research placement at Peking University in Beijing, China.  He used time-depedent Hartree-Fock (TDHF) to look at the part of the fission pathway near scission where the TDHF method is applicable, and to study how different parameterisation of the nuclear force give different predictions for the pathway to fission.  It's a short piece of original research, which complements nicely the mix of other research and review articles in the Special Topic.  I worked on this project with Marko and his host supervisor, and am co-author on the paper.  I took the liberty of using a picture from this paper as an accompaniment to this blog post.

Once the two remamining papers appear,  on spontaneous fission and collective dynamics with a transport model, have appeared, the whole Special Topic will be avaiable as a free e-book, in pdf and epub format, so get your Kindles ready.

Friday, 7 August 2020

Deep Summer in Bishop's Stortford


It's a strange time right now, of course, with the Covid-19 pandemic ongoing.  I've been taking summer holiday in the form of working a couple of days per week and having more days off than on.  This week, I'm on holiday, and we have made a trip to visit my parents, following both our households isolating for an extended period.  I don't have a car, which is usually no problem, but we didn't fancy travelling by public transport right now, and fortunately my parents came to pick us up and bring us all up to their house, while my mother-in-law lent us her car, too, so that we could have the two-cars needed for the 6 of us.

So ... we have been carrying on the lifestyle of staying in and isolating from other people with the exception of my parents, at their house. It's nice spending so much time with them.  They've lived in this house for more than twenty years, and this two-week visit is the longest time I have continuously been here.  With 4 kids to play with and look after, there is no shortage of things to do, and my parents have (unlike us at home) subscriptions to the likes of Disney+ and Netflix.  

While I've been working just enough to keep up with MSc, PhD and undergraduate summer project students, a paper I worked on as part of a large supergroup of theorists to map out the next steps in understanding nuclear fission from a microscopic point of view was published.  It's a comprehensive (86 page!) paper bringing together expertise from a lot of different people to try to figure out how to move towards a unified theory of fission, a process which consists of many stages, operating a different timescales, with different degrees of freedom coming into play;  this calls out for a different range of approximations for each stage, and an understanding of how to link them together ideally with a single framework.  The paper is an attempt to put down all our ideas on how to proceed here.  I contributed what I could to those parts I felt sufficiently expert in, and the whole paper was put together by Prof Dobaczewski from the University of York.  It's available now, via its doi: 10.1088/1361-6471/abab4f, though it has not yet been assigned a page or article number.  Because there are UK-based co-authors, it is fully open-access, as is the case with all J Phys G papers with UK authors.

At the top is a picture of me photobombing my 8 month old son Kit, outside at my parents' house.