Tuesday, 22 April 2014

Back to the old house


After a week off of work, it's off to Tennessee for me.  Oak Ridge, where I'm heading first, is my old stomping ground - hence the title of this post and its musical accompaniment.  Unlike the song, I do like going back, though it does always evoke memories going back to somewhere I spent quite a few years living.  My trip to Oak Ridge will be pretty fleeting - for a couple of days to give an invited seminar to the Physics Division - but followed by my first ever visit to Nashville, to visit a friend and collaborator at Vanderbilt University.  For some strange reason, when living in Oak Ridge, I never did make it to Nashville, despite making road trips as far afield as New York City and New Orleans... Still, finally fixing that, 

No doubt I will have cause to include musical accompaniments to my blog posts when in Nashville that are a little different to The Smiths.

Tuesday, 15 April 2014

April 2014 Graduation

After the IoP conference drew to a close on Wednesday, I had a day off, then on Friday, there was our postgraduate graduation ceremony.  It happens once a year, and includes all those who have finished their taught postgraduate courses (MScs, mostly, amongst the Physics Department) or PhDs.  I almost always attend the undergraduate graduation ceremonies, featuring our undergraduate students, but usually reserve the postgraduate ceremonies for those when I know there will be students in it that I have taught.  My teaching is heavily focused on undergraduates rather the MSc students, so I tend to go just to those PG ceremonies that I have PhD students graduating at.  This one was the one where my (now ex-)student Chris would be due to attend, so I signed up.  I realised on the day that I didn’t actually know if Chris would choose to attend the ceremony, despite being eligible and having a post-doc job in the University.  It seemed likely, but you can never tell… Fortunately, as I was wandering to the place where the graduation robes are doled out, I bumped into Chris, who was heading there for the same thing.

Graduation ceremonies are nice because you see the person of interest to you graduating, and a little boring because you see a lot of people you don’t know doing the same thing.  Perhaps for the likes of me it is more interesting because I am bound to know a higher fraction of the graduands than a general member of the audience is.  In fact, even though I didn’t directly teach the Physics MSc cohort that was graduating, I did know a bunch of the from their undergraduate days, and they had re-enrolled for another degree.  


It was too bad that I couldn’t go to the post-ceremony genteel garden party afterwards, to chat to Chris and see his dad again, who I hadn’t seen since he came along on the day I interviewed Chris for his Phd about 4 years ago.  I had to meet with a current PhD student and then head off to give a talk about the use of nuclear physics in geology to the West Sussex Geological Society.  But that deserves a whole separate post of its own…

Wednesday, 9 April 2014

IoP conference day 2


The pre-dinner reception
was going on through this
window!
Day two of the IoP Nuclear Physics Conference is the only completely full day.  It was pretty full of shorter parallel talks by students and postdocs - which is really the heart of the the national conference, but I only made notes to blog from from the first, plenary, session of invited talks.  Here's a summary:

The morning session kicked off with Evgenny Epelbaum talking about Chiral approaches to nuclear forces.  This method builds up nuclear forces and allows nuclear structure calculations from basic QCD-inspired ideas.  Evgenny presented results including the famous Hoyle state in Carbon, reproducing the energy pretty well.

Next up, Gary Simpson from the University of the West of Scotland, looking at what happens to the structure of tin isotopes, as one looks at very heavy exotic isotopes beyond Sn-132.  Some theories suggest that N=90 might be a local magic number and lead to a surprisingly stable Sn-140 isotope, which may have a strong influence on explosive nuclear processes in stars.  With Sn-132 already being pretty exotic, it’s quite some thing to suggest that one could then look at a substantial extension to the tin isotopes, but thanks to the RIKEN facility, they’ve now made it out to Sn-142.  

Andrei Andreyev talked about a series of results of properties of nuclei in the vicinity of lead.  In their experiments, they produce their nuclei by firing protons at Uranium targets, and produce a whole slew of reaction and decay products.  Here, Andrei concentrated on spallation reactions, which give resulting nuclei a bit lighter than Uranium, and in particular produced may results of astatine isotopes.  Astatine is often quoted as the rarest isotope found on Earth, with only a fraction of a gram in the Earth’s crust at any one time.  Their work included the first determination of the chemical ionisation potential of astatine.  Go nuclear physics!


The final plenary talk of the morning was by Judith McGovern whose talk was on proton polarisabilities from Compton Scattering.  Scattering photons off of protons is not as simple as it might seem, thanks to the size and structure of the proton.  Thanks to the presence of charged objects inside protons (i.e. quarks), the electric field associated with photons can cause a separation and movement of charges inside the proton and cause knock on effects on the scattered photon, such as a polarisation of the light. Judith presented some of the important questions and attempts to find theoretical resolutions, including some of the intriguing recent results like the apparent measurement of a much smaller proton than previously thought. 

The next three session were all parallel, so clearly I only saw half the remaining talks.  I was pleased with how my student did, and it was encouraging that he got lots of interesting questions afterwards, which then prompted a discussion in the break afterwards, which gave us a list of calculations to make that can keep us occupied for a long time.
The evening featured the conference dinner, which is a nice highlight of all conferences.  It's not really a way of wasting research money on fine dining, but rather an important part of community cohesion for a group of people that spend most of the year not seeing each other, but having to work as a unified community at various points (e.g. when interacting with funding agencies).  The UK conference is good place for new students to get to
know each other and the community's old hands.   Over dinner, some of us old hands talked about famous events from old conferences, and hopefully some of the students here this week will be doing the same at an IoP Nuclear Conference in many years from now.

I've interspersed some pictures taken at the dinner through the post.

Monday, 7 April 2014

IoP Nuclear Conf Day 1

So, today was the first day of the IoP Nuclear Physics Conference, which I am chairing, in Croydon.  It's also my daughter Alba's first ever physics conference, and I do think she was rather the star of the show.  Though only present in breaks, she was certainly the centre of attention at those times.  Still;  There was some nuclear physics going on too.

The day started with the STFC Town Meeting.  Lots of STFC people came along, including Chief Exec John Womersley, which was a gratifying indication of the extent to which STFC support Nuclear Physics (we can sometimes feel a bit unloved, you see).  This dealt with matters of funding, the politics and the practice, and was interesting enough, though I was more or less already up to speed with what was being talked about - all except the Newton Fund, which might provide some useful streams of funding for probably more trips to India (which will suit me just fine).

After lunch I had the welcome talk to give that I mentioned in the last post.  I managed to string that out to 20 minutes or so.  The most entertaining bit, I think, was when I produced a prodigious list of past locations of the IoP conference.  It was all thanks to an e-mail from John Smith of the University of the West of Scotland from around a year ago when we were looking where the next conference should be.  His memory on the matter was particularly impressive, and he came up with the following list:

2013 York
2012 Brighton
2011 Glasgow
2010 Edinburgh
2009 Birmingham
2008 Liverpool
2007 Surrey
2006 York
2005 Manchester
2004 Edinburgh
2003 Glasgow
2002 Brighton (with particle physics)
2001 Bergen (Norway)
2000 Birmingham
1999 Salford
1998 Liverpool
1997 York
1996 Amsterdam
1995 Telford (with particle physics)
1994 Brighton (IOP Congress)
1993 Glasgow
1992 Edinburgh?
1991 York?
1990 Strasbourg?


Can anyone in the nuclear physics community do any better than that?  Extend the list back?  The first one I went to was the 2001 Bergen conference.  This lives on in my memory for the conference dinner.  Though the IoP conference is usually a national affair, every now and then it branched out to slightly wider regions.  The Bergen conference was a "North West Europe" Nuclear Physics conference, featuring only countries in the NW of Europe and with smallish nuclear physics communities - so excluding France and Germany.  The UK then had one of, if not the, largest delegations.  That being the case, there were a few troublesome vegetarian attendees who requested a veggie option for the conference dinner.  We were assured that this would be okay.  Come conference dinner time, the host gave a speech, and the introduced the food.  "Now, for dinner, we have Hungarian Goulash.  With rice.  Vegetarians - make sure you get in quickly to get lots of rice."  He wasn't joking.

Ironically, tonight, the vegetarian option was butternut squash risotto (which every vegetarian knows is the thing that places who don't do vegetarian food think vegetarians like).  Only, they ran out after about half the diners had gone to the buffet.  They replaced it with ... a large dish of rice.

So - anyway, after my intro talk, we had Kara Lynch, Adelle Hay, Victoria Truesdale, Rosa Romita and Elizabeth Cunningham talking about laser spectroscopy, nuclear data, fission fragment spectroscopy, quark-gluon plasma and outreach.  My introductory talk made sure the gender bias was not too extreme.




Saturday, 5 April 2014

IoP Nuclear Physics Conference 2014

On Monday I'm off to the annual national nuclear physics conference, organised under the auspices of the Institute of Physics's Nuclear Physics Group.  It's particularly important that I attend this year, as I am the conference chair.  I've been involved in organising conferences before, but this is really the first time I've been Mr Chairman.  Or Dr Chairperson.  Thankfully, the Institute of Physics conference team have done lots of the administrative stuff, leaving me and the organising committee to do the scientific stuff.  I hope it all goes well.  I think everything is set.  Well, almost everything.

When creating the timetable, we (the organising committee) based it last year's conference.  This had a timetabled "welcome" address by the organiser at the beginning.  We've put the same thing in, which means that I need to open the conference with a welcome address.  All very reasonable.  Only the slot is 30 minutes long.  Less reasonable, I think.  In retrospect, it might have been sensible to reduce this to 10 minutes.  Still, as anyone who knows me can attest, I can easily go on and on and on, and fill any time slot given to me.  Apologies in advance to other attendees :-)

The image attached to this post is the hotel where the conference is taking place, featuring some of the very same blades of grass that people will be longing staring at during the welcome speech.

Monday, 31 March 2014

And nature does it in real-time

A paper of mine appeared today in Physical Review E.  Called, "Extension of the continuum time-dependent Hartree-Fock method to proton states1."  As the name suggests, it is a paper about methodology - so it's not going to feature in any press-releases about exciting new physics results.  It's even an extension to an existing method (from our previous paper), which might make it seem all the less exciting.  I think it's still a good paper, and a useful one, hence the blog post.

The method we developed overcomes a problem inherent in many attempts to solve time-dependent equations in physics problems.  From a mathematical point of view, the problem is that the equations that nature seems to have written itself in are differential equations.  By their very nature, such equations have solutions which combine some functional form, along with boundary conditions.  The functional form gives a kind of general prescription of how to solve the equations for absolutely any case at all, and the boundary conditions then shape the details to fit the exact physical situation at hand.  For example, the general solutions to Maxwell's equations describe all (classical) electromagnetic phenomena, but the boundary conditions pin down whether the particular solutions is for a light wave, the electric field round a charge, or the induction in a generator.  

In the case of our paper, we were concerned with the time-dependent Schrödinger equation - the basic equation of quantum mechanics2.  In particular, we are interested in solving it for the case of atomic nuclei undergoing some kind of dynamic process.  In mind we have excited wobbling states, or fusion or fission, or some combination of such things.  More or less any case of interest involves the nucleus being excited in such a way that it can decay by breaking up, either into two or more fragments, or by emitting protons or neutrons.  One long-standing problem with solving the time-dependent Schrödinger equation in such cases is that the only simple ways of working with boundary conditions are to assume that we can consider the tiny nucleus to be little box, okay a bit less tiny than the nucleus, but a box which either reflects back anything emitted from the excited nucleus, or which lets things pass through but then reappear at the other side. This is kinda bad:  Nature doesn't do it that way.  It lets things that decay off of the nucleus travel far away without some artificial box getting in the way.  The reason that these strange unphysical solutions are the easy ones to implement is that they involve pretending that the inside of the box is everything that there is.  If we have stuff in our system, it has to be somewhere in the box.  It's hard to start having by having a bunch of stuff (nucleons in a nucleus) in our calculation, and then to keep calculating how it changes in time, but to stop keeping track of some of it because it's left our system.  It doesn't sound like a hard problem, or even that it should be a problem at all, but it is, on both counts.

So, our paper is about how to deal with this "open quantum system" (search for that phrase, and there are a whole load of hits - it's a field in itself).  Our method is reasonably general, but we've applied it just to vibrational states of nuclei so far.  That was quite a job in itself.  It is the final work from my PhD student Chris Pardi's thesis, from last year.  It took the paper a while to get into print.  We tried first in Physical Review C, where it was felt to concentrate a bit too much on the technical aspects of the algorithm, and not enough on the nuclear physics - a fair enough comment - and so we asked Physical Review E to take a look.  One referee it was sent to was nice enough to write a long report, ending with "In conclusion, I believe that this paper is excellent and very well written." So - thank you anonymous referee.

The title of this post is a reflection of the fact that we have worked hard to solve some equations, along with their proper boundary conditions, using some computational calculations that take a certain time to run.  Not so very long on the scale of things, but still a few tens of seconds.  They describe a process that happens in nature over a few zeptoseconds.  Nature works out what to do so quickly...



1 C. I. Pardi, P. D. Stevenson and K. Xu (2014). Extension of the continuum time-dependent Hartree-Fock method to proton states Physical Review E, 89 : 10.1103/PhysRevE.89.033312
2 Okay, we could debate what the most basic equation of quantum mechanics is, but calling the Schrödinger equation the basic one is not outrageous.

Tuesday, 25 March 2014

STAGgering!

A new blog has been set up here at the University of Surrey, on which I have write-access.  I have yet to write anything there, but when I am struck to write something which is a bit more about Higher Education than nuclear physics, then that is probably where it will go.  Other more erudite people than me will also be writing there, and indeed already have started.

The blog is called STAGgering, a fun play on the fact that the University is on a site called Stag Hill, and the stag features in the University's logo.  Ostensibly it's about this particular university, but I expect the there will be lots of stuff about the higher education scene in general, so if that's your thing, then please add it to your list of blogs to follow.

The picture with this post is a rather old one, from the early days of the University.  I think the fence you can see in the background is fencing off some building work of what is now the Guildford Court residence block.  The picture is from the great website uossnaps, set up by a past student to share old photos and memories of the place.