Archive for October, 2009

A different interpretation of super-dense matter?

Posted in Uncategorized on October 29, 2009 by quantummoxie

I gave a talk yesterday as part of our new seminar series at work.  It was based on my FQXi essay.  One of the issues I raised was how to describe degenerate matter on a massive scale, specifically white dwarf stars.  Normal stars are supported against gravitational collapse by the stellar fusion process.  But stellar fusion has stopped in white dwarfs and the accepted explanation for the non-collapse of white dwarf stars is that electron degeneracy pressure couteracts gravitation.  Electron degeneracy pressure is a consequence of the Pauli exclusion principle.

One of the points I make in my essay is that, normally, we associate forces with interactions in which some kind of information is exchanged.  If we assume this definition of force, how do we draw a free-body diagram for a chunk of white dwarf star?  By this definition of forces, there is only an inward one – gravity.  This may not seem like a major problem since it is confined to a highly specialized area of research.  We don’t encounter white dwarf stars on an everyday basis.  But with an increasing amount of research – and even technology – probing the quantum-classical boundary, we will need to address this issue if we expect our descriptions of nature to be self-consistent.

Aside from that issue, however, a colleague of mine in the chemistry department posed an intriguing question: “I still wonder whether the necessary increase in energy that accompanies greater spatial confinement according to the uncertainty principle is an equally valid explanation for the failure of anything to fully collapse.  (Albeit one which is not one of the 4 forces.)”

That got me thinking.  So, first of all, he wondered why it wasn’t just electromagnetism that prevented a white dwarf from collapsing.  The answer to this is that they are known to be so dense that the individual particles are presumably closer than they could have gotten if it was an electrostatic repulsion preventing such a thing, i.e. an electrostatic explanation doesn’t jive with the experimental data.  At least that’s been my understanding of the problem.  Given that, then, I wondered if perhaps there was a way to get something to be even more dense than degenerate matter without its complete collapse using his criteria – the uncertainty principle.  Or, perhaps, this is really what is at the heart of what prevents super-dense bosonic matter from collapsing, e.g. Bose-Einstein condensates, which we know have their own analogue of exclusion that prevents complete collapse.  Either way, the example of the white dwarf (or even a neutron star) begs the question: just how close can two fermions get before exclusion prevents them from getting any closer?  This is, perhaps, related to the question: how close do two particles (for example, two electrons forming a Cooper pair) have to be before they can be considered a system, particularly considering that electromagnetism has an infinite range?

These are some intriguing questions that I don’t have answers to yet.  I’d be curious to know the thoughts of anyone else out there who has, perhaps, more experience in this line of inquiry.


Physics in Zürich – historical sites

Posted in Uncategorized on October 24, 2009 by quantummoxie

Long time, no blog!  Yes, I’ve been insanely busy.  One thing I was busy doing was preparing for QIP 2010 that will take place in Zürich in January.  Now that I’ve made my reservations, I’m compiling a list of places in and around the city that have played a role in the history of physics.  Notably, of course, both Einstein and Pauli spent a great deal of time in Zürich.  Einstein received his PhD from the Universität Zürich and later taught at ETH (the Swiss Federal Technical Institute).  Pauli taught at ETH for many years prior to WWII and returned to Zürich after the war.  He died in Rotkreuz Hospital in Zürich.  In addition to Einstein and Pauli, Zürich was also the home (and final resting place) of the author James Joyce who first coined the term ‘quark’ that was later used by Murray Gell-Mann as a name for the now famous sub-atomic particle (apparently Gell-Mann had wanted to name it after the sound a duck makes and then stumbled across Joyce’s word while reading Finnegan’s Wake).

In my online searching for interesting physics-related sites I set about attempting to find out where these folks lived while they were in Zürich so that I can visit there myself come January.  To my surprise and pleasure the City Archives not only have a list of all of Einstein’s addresses while in Zürich, but they also include photographs of the homes.  While there were no entries listed for Pauli, I was able to find Joyce’s address.  Joyce also happens to be buried in the historic Fluntern Cemetery, thus a visit to his grave is fairly simple.  Finding Pauli’s final resting place has proven a bit difficult as have his homes though I did find out that ETH’s new suburban campus has named a street after him (Wolfgang-Pauli-Strasse).  In an Editorial in Physics in Perspective from 1999, John Rigden mentions that he visited Pauli’s grave in Zürich, but fails to mention where it is despite the fact that he also mentioned that the late Mrs. Pauli, who was alive at the time, was “delighted” someone was visiting her husband’s grave.

So, if any of you fair readers are familiar with Zürich and happen to know where Pauli is buried and/or where he lived, please let me know.  If you know any other physics-related historic sites (aside from ETH and the Universität Zürich) please post them here.

FQXi essay contest – making progress

Posted in Uncategorized on October 16, 2009 by quantummoxie

Well, my essay seems to be creeping up in the Community Ratings.  I’m currently tied for third place.  That’s kind of cool, right?  I’m keeping my fingers crossed.  I’d really like to have a strong finish.  If you haven’t read it and/or rated it yet, the public can still do so.  You can do both here.

Playing pong with sheep

Posted in Uncategorized on October 13, 2009 by quantummoxie

Yes, some people have a little too much time on their hands (though, note, that it was sponsored by Samsung so they presumably were paid to do this).  For some reason WordPress’s video embedding isn’t working properly, so you’ll have to follow this link.

FQXi essay – so far

Posted in Uncategorized on October 12, 2009 by quantummoxie

Well, I’m doing alright, but not great, in the FQXi essay contest so far.  Comments and ratings may be viewed here.  Please read and vote on this if you can (be honest with your vote).

Israel Gel’fand (1913-2009)

Posted in Uncategorized on October 6, 2009 by quantummoxie

Via The Pontiff, noted mathematician Israel Gel’fand has passed away at age 96.  He was truly a remarkable mathematician who took an interest in mathematics education.  In fact he often let his research and teaching influence each other as described here (quoting from two written papers):

One of the characteristic features of Israil Moiseevic’s activities has been the extremely close bond between his research work and his teaching. The formulation of new problems and unexpected questions, a tendency to look at even well known things from a new point of view characterises Gelfand as a teacher, regardless of whether at a given moment he is holding a conversation with schoolchildren or with his own colleagues.

In 1994 he was awarded a MacArthur “Genius Award” for his work in mathematics education, particularly in relation to correspondence education.

FQXi essay contest

Posted in Uncategorized on October 5, 2009 by quantummoxie

I have entered an essay titled “Unification and Emergence in Physics: the Problem of Articulation” for the latest FQXi essay contest.  I would appreciate comments over on that site (clicking on the title in the previous sentence will take you straight to the discussion board for the essay).  Please vote if you do read it.  Vote honestly, though, so if you don’t like it don’t give it a high rating.  I just ask that you read it carefully and give it some thought before you vote.  I don’t know when voting stops.  Thanks in advance!