Things of beauty


nature physics | VOL 6 | MARCH 2010 | www.nature.com/naturephysics 147

editorial

What is the most beautiful concept in 
physics? Answers to that question will be 
many and diverse — depending on whom 
you ask, their background and ‘soft spots’, 
on their teachers, and on personal 
‘light bulb’ moments. There are ideas in 
physics that strike us as simply beautiful 
from the first moment we encounter them: 
their full implications and significance still 
far from apparent, they seem to have an 
innate and inevitable elegance.

For many, and certainly for those who 
have a weakness for quantum mechanics, 
the Aharonov–Bohm effect is among those 
‘beautiful things’. The very idea is intriguing: 
that a solenoid can have a measurable effect 
on a charged particle even if the particle 
never passes through a region where either 
the solenoid’s electric or magnetic fields are 
non-zero. But the implications are of course 
much broader.

Last year marked 50 years since its 
discovery. Writing on page 160 of this 
issue, Murray Peshkin and Lev Vaidman 
survey an “intellectually delicious” meeting 

that took place, in December 2009, at the 
birthplace of the effect, the H. H. Wills 
Physics Laboratory in Bristol. The event 
celebrated the fiftieth anniversary of the 
discovery of the Aharonov–Bohm effect, 
and also 25 years since the discovery of 
Berry’s phase, another (and not unrelated) 

concept that, for all its many ramifications, 
also charms physicists with its inherent 
beauty. On page 148, Sir Michael Berry 
recollects the events surrounding his famous 
1984 paper, discussing both the work that 
followed shortly after and the anticipations 
of the geometric phase that preceded his 
own. “In retrospect what we call ‘discovery’ 
sometimes looks more like emergence 
into the air from subterranean intellectual 
currents”, says Sir Michael.

There is much more still to emerge from 
the 50-year-old Aharonov–Bohm effect, 
which may well have impact on the very 
foundations of quantum physics. Indeed, 
on page 151 Sandu Popescu argues that the 
deepest implication of the effect has been 
widely ignored so far — and that, without 
it, a real understanding of the nature of 
quantum mechanics is impossible.

When John Keats wrote his 1818 poem 
Endymion it wasn’t physics he had in mind, 
but his famous opening line rings true in 
this case too: “A thing of beauty is a joy 
for ever”. ❐

The celebration of 50 years of the Aharonov–Bohm effect, and 25 years of Berry’s phase, is a celebration 
of the elegance of physics.

Things of beauty

Funding of the arXiv preprint server must now be shared by more of its users.

Treasured archive

The arXiv preprint server has become 
central to the working lives of most 
physicists: ‘checking the arXiv’ is the 
starting point of many a daily routine. 
Founded by Paul Ginsparg, the arXiv has 
expanded to include not only physics — 
astrophysics, condensed matter, and high-
energy physics being heavily represented — 
but also mathematics, computer science, 
quantitative biology and even quantitative 
finance. The arXiv now hosts nearly 
600,000 preprints from 101,000 registered 
submitters in 200 countries, and serves 
more than 2.5 million article downloads 
every month to 400,000 users.

The statistics are remarkable. And it 
is also remarkable that, having initially 
been hosted at the Los Alamos National 
Laboratory, the server has in recent 
years been funded and managed by a 
single institute, Cornell University. Now 

the operating costs of the ever-growing 
arXiv match the entire Cornell library 
budget for physics and astronomy, and 
the university has made a plea for help in 
funding it.

As a short-term solution, Cornell is 
approaching the top 200 user-institutions 
of the arXiv — who account for 75% of 
institutional downloads — for a financial 
contribution to the maintenance of 
the arXiv. It is heartening that help has 
already been promised from several large 
universities and laboratories, but wider 
support is still being sought. For the longer 
term, Cornell will assess, with those who 
come forward to support the arXiv, what 
the options are in developing a sustainable 
model for the future.

Secure, ongoing funding of the preprint 
server is vital, and surely deserves at 
least national endorsement from US 

funding bodies, if not some international 
arrangement. The fast communication 
of results — data or theory — between 
experts that the arXiv facilitates is a boon 
to physics, and one well recognized by the 
Nature Publishing Group: any submission 
to Nature Physics or its sister journals may 
be posted, in that original submitted form, 
on the preprint server (although we do 
ask that the final, revised and accepted 
version is not posted until six months after 
publication in the journal; the published 
version, in the Nature Physics layout, may 
not be posted).

It’s up to physicists now to sustain 
their arXiv, encouraging their institutions’ 
libraries in particular to engage in its 
development. More information is available 
at http://arxiv.org/help/support; and 
comments and suggestions may be sent to 
support@arxiv.org. ❐

M
. B

er
ry

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http://arxiv.org/help/support
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	Things of beauty