Tuesday, 15 September 2015

From COMEX5 in Krakow

I'm at a conference in Krakow, Poland.  The conference is called COMEX5.  My other half said it sounded like a comic convention.  It's not, but it does indeed share a name with a convention which took place in Singapore a couple of weeks ago.

The COMEX title is an abbreviation of "Collective Motion in Exotic Nuclei."  Despite this being the series's fifth outing, it is really quite a venerable conference series, it being a re-branding of the Giant Resonance conference.  Giant resonances are the main topic of the conference.  They are vibrational states which are very collective in nature, meaning that they feature the action of all nucleons in the nucleus.  Their observation dates back to the mid 1930s when at least the first hint was seen (by Bothe and Gentner in Heidelberg).

I'm giving a talk here on Thursday about using time-dependent methods to describe these resonances, and what is shows about the underlying structure of the nuclei.  I also, of course, take part in the organised events during the conference, such as the reception in Krakow's beautiful Collegium Maius, as pictured.

Thursday, 10 September 2015

Suggestions from PRL

Last month, I commented about the high proportion of articles in the nuclear physics section of Physical Review Letters that are in the sub-field of relativistic heavy ion collisions (RHIC) and how they form the preponderance of articles promoted by the editors to appear on the journal front page.   In the last month, the trend has continued, and only RHIC papers have been highlighted.  So, let me highlight here a paper which was published last month, and has been picked up by a few news websites:

The paper is called "Direct measurement of the mass difference of 163Ho and 163Dy solves the Q-value puzzle for the neutrino mass determination."  The physics motivation behind the work is that the nuclear reaction:
163Ho + e163Dy + νe
can be used as a model-independnt (i.e. not relying on assumptions about the structure of the nucleus that may not be correct) mans of determining the mass of the electron neutrino -- something that is not pinned-down at all well.  The mass of the neutrino is known to be extremely small, but not zero.  By observing the above reaction, and using conservation of energy, one can work out the energy balance (the "Q-value" of the title) from the observed particles, and deduce the energy carried off by the (unobserved) neutrino, and hence its mass.  To be able to do this, the masses of the two nuclear isotopes in the equation: Holmium–163 and Dysprosium–163 must be known to very high accuracy.  Actually -- it is only the difference between the two masses that needs to be known, and there is disagreement in the published data what this difference is, to a level that swamps the tiny neutrino mass.

The experimenters here used a Penning trap to store ions of each of the isotopes.  For a given particle of mass m and charge q moving in a trap with magnetic field B, the particle will move in a circle with frequency f=qB/(2πm).  Measuring the frequency allows a value of the mass to be determined.  They put the two different ions in the same trap at the same time, but in separate bunches, reducing systematic effects to do with e.g. variations in the magnetic field.  They concluded that their value for the mass difference is at variance with the "accepted" value (that published in the Atomic Mass Evalution) by more than 7 times the size of their error bar.  Thus, the error in determining the neutrino mass should be able to be reduced in future experiments looking at the reaction above.

Saturday, 5 September 2015

Anti-migration sentiment in Guildford

There has been much in the news recently giving a reminder that many other people in the world find themselves in a wretched situation and are in terrible danger.  Like other humans since the dawn of our species, they wish to wander or migrate to where they hope to find a better life.  

Here in the UK, immigration was more or less unrestricted in the 19th century and the beginning of the 20th up to the First World War.  These days, restricting immigration seems to be a major policy of the main political parties.  Belatedly, our government has agreed a somewhat mealy-mouthed acceptance that Britain can play a part in giving some of our displaced and frightened fellow humans a more stable life.  It's a start.  I have signed the petition calling on the government to accept more asylum seekers and refugee migrants in the UK.  It's been a particularly successful petition on the government's official petition web site, having attracted 400,000 signatures thus far.  100,000 are needed to force a debate on the matter in parliament, and perhaps it was part of the reason that the government acted.  

I note, though, that on the government petition website, at the time of writing, a reactionary petition to cease all immigration into the UK is currently accumulating signatures at a higher rate, as the picture below shows.
This brings me to the more on-topic part of my post.  On-topic, in the sense that this blog is purportedly about nuclear physics and life in academia in the UK.

While walking along a footpath in Guildford a couple of days ago, I spotted a sign, shown below, saying "A no students zone":

Someone had gone to the effort of making a bunch of these, and sticking them on lampposts around town.  Now, I can't speak for the person who did this (but if they chance to find this blog post, I'd welcome them to post and give their view) but one doesn't have to go too far to find people who don't want students to come and live in the same town as them.  This is another migration issue, though one that includes national, as opposed to solely international, migration, and one in which the migrants are typically not in the most distressing circumstances.  

I'm not sure of the whole gamut of reasons why residents are against this particular kind of migration, but an opinion piece in a local web site suggests that the pressure on housing is one reason.  A local political party which won council seats (more seats than Labour) wants the students segregated, though how they propose to deny citizens access to the private rental sector is not something I've found on their website.  I can certainly understand anyone's frustration that it is hard to afford somewhere to live in Guildford, but blaming migrants is never the right answer.  It may appear the proximate cause of one's woes, but blaming the person who happened to arrive in the area later than you or your ancestors did is not conducive to any kind of reasonable solution.

I should perhaps disclose that I wasn't born in Guildford, but now live here.  I always thought that was an acceptable thing to do, though I did move from the place of my birth as a 5 year old.

To end on a positive note for the burghers of Guildford;  The government petition website lets you see what the local breakdown of popular petitions is.  I showed above how the petition to stop immigrants coming to the UK is currently getting more signatures then the one supporting the settling of refugees.  In Guildford, the one to accept migrants is top of the list and the one to stop them features nowhere on it.  Second on the list from Guildford is to debate a vote of no confidence on Health Secretary, and Surrey MP, Jeremy Hunt.  I guess that's a doubly-positive note to end with.

Tuesday, 1 September 2015

September in Preview

Who let it be September, already?  

Actually, it's seemed rather Septemberal for a while.  Yesterday was the late August bank holiday, and it never seemed to get very bright here in Guildford, with the sky overcast all day, and drizzle falling for much of it.  The picture attached to this post is from my holiday last week, showing a typical scene (though it had stopped raining for the picture itself).

September means back-to-school time, but only kids -- at my University, at least, the students don't come back until 5th October, with new starters coming for the week leading up to that date.   Freshers' week is usually a busy time for me.  At least, it has been over the last several years, as I've been a Warden on campus.  This means I live on campus, in the student accommodation blocks, and act as a kind of hybrid between a policeman, a headmaster, and a social worker.  It's been an interesting job.  Sometimes enjoyable, sometimes not so much, but doing a second job for seven years and having free accommodation have enabled me to buy a place to live in Guildford, which is no mean feat.  So -- September means moving house for me.  I remember from previous occasions of doing it that moving house is not a particularly pleasurable experience... but it will be nice to be in a home of my own.  

Shortly after moving, I'm going to conference #2 of the summer.  It's called COMEX5, which abbreviation stands for Collective Motion in Exotic Nuclei Under Extreme Conditions.  I'm looking forward to that.  It's in Krakow, Poland, which is a nice place to spend a week, and I'm sure to get a bunch of interesting ideas from the talks (excepting my own).  After I get back, there'll be a final week of undergraduates not being here, followed by the arrival of the new students.  Exciting!  It looks like we've got another bumper year in terms of student intake, and that ~120 is our new norm

Tuesday, 25 August 2015

Kelvin in Kent

I'm on holiday for a week with my family.  We're staying in Deal, in Kent.  So far, it has rained in an unseasonable way, with reports on the TV news this evening that there has been flooding in parts of Kent.  Right now, I am looking over a view of the English Channel, and although very overcast, it's not raining.  I can't see France across the water, though, which you can do even on a moderately clear day.

The picture shows a current snapshot of rainfall. The wind is from the southwest at the moment, and that heavy rain in the North Sea was over us not long ago.  It's not looking terribly likely that things will get too much better over the next few days.  

Fortunately we are staying in a wonderful house, thanks to the kindness of some friends of my parents, whose house it is.  They are letting us use it while they are away.  The bookshelves are full of some great books -- including some that a physicist would find particularly interesting.  There are some biographies of famous physicists;  I've started reading Sir Oliver Lodge's autobiography, and there are several books about Lord Kelvin.  It turns out that the owner of the house is a direct descendant of Lord Kelvin.  Now, if only the temperature were a little higher on the Kelvin scale, our holiday may be a bit more fun...

Sunday, 23 August 2015

Notre Dame

I've just made a visit to the University of Notre Dame, in Indiana, USA.  I was there to visit one of our MPhys undergraduate masters'  students who is spending a year there on placement on a project to do with neutron capture reactions in stars.  As I often do, I took a picture of the student at the facility where he is working.  The picture is slightly misleading, as we were both on a tour of the experimental nuclear physics facilities in the Physics Department, and it was the first time either of us had seen it.  Abdellatif, the student pictured, is working on a theoretical project, and doesn't ever step into the lab, lest the theory-waves break the equipment.

The University of Notre Dame have been (and continue to be) wonderful supporters of our MPhys programme over the years.  I had never been there before, but now that I am the director of the MPhys Research Year programme, I wanted to come to show my appreciation to them for supporting our students.  Of course, they get in return some excellent junior researchers who can really do important work for their research programme.  Most, if not all, of our MPhys students publish papers as a result of their research year work, and the majority go on to do PhDs and many then get faculty positions (though some forge more successful careers).  In fact, Abdellatif is being supervised in his project by a Notre Dame faculty member who was a Surrey MPhys student around 15 years ago, who in her time was on a research placement.  

Tuesday, 11 August 2015

Relativistic bias

As it's summer, I find I have the time more often to just browse recent results in nuclear physics.  One way of doing this is to go to the Physics Review Letters (PRL) website, and look at all the recent papers in the Nuclear Physics section.

If I do this, I see many interesting papers;  Some recent Earth-based determinations of reaction rates for nuclear reactions that take place in stars and which are important in understanding stellar evolution;  Some neat calculations of how nuclei can stretch into rod shapes as they rotate very fast;  The observation of a new and really exotic nucleus -- an isotope of hyper-hydrogen;  a new "soft" excitation mode in Lithium-11, itself a really interesting nucleus which is as large as a nucleus of lead despite having around 200 fewer nucleons in it.

What struck me most immediately about the list is that there were three papers among the 25 on the list that were "Editors' Suggestions" and that they were all from the sub-field of relativistic heavy-ion collisions.  Editors' Suggestions are exactly what the name suggests, and they get promoted within the Physical Review Letters website, appearing in the Highlights section.   From looking at the papers involved, I find it hard to conclude anything but that the editors involved in the relativistic heavy-ion papers are more active and zealous in promoting papers in their area than editors involved in the rest of nuclear physics.  I realise PRL has a history of publishing quite a high proportion of relativistic heavy-ion collision papers compared with other nuclear physics journals, perhaps thanks to its geographical ties to Brookhaven Lab, but I had not quite realised the obvious editorial differences between the sub-fields.

Anyway, attached to this plot is a pretty picture of some stretched-out Carbon isotopes from the preprint version of the rod-shaped nucleus paper mentioned above.