James Overduin's Web
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Background
Welcome to
my internet home. I joined the Department of Physics, Astronomy and
Geosciences at Towson University as a full-time faculty member in August
2009. Prior to that I spent 5 years (2003-8) as a Visiting Scientist with the
Gravity Probe B (GP-B)
and the Satellite Test of
the Equivalence Principle (STEP) experiments at Stanford University.
Earlier, I worked as a JSPS (Japan Society for the Promotion of Science)
Postdoctoral Fellow at Waseda University in Tokyo, Japan (2001-3) and an
Alexander von Humboldt Fellow at the University of Bonn
in Germany (2000-1). I obtained my PhD from the University of Victoria
(1998) and my MSc from the University of Waterloo
(1992) with a thesis based on research carried out at the Space Sciences Laboratory at the
University of California, Berkeley (1991). My BSc
(1989) is from Waterloo. To date I have published two books and 50 research
articles. Research
I am
especially interested in the interface between the fields of gravitation,
cosmology and high-energy physics. There is discovery potential here, not
just because so much remains to be explained, but because many of the leading
explanations are becoming testable, either now or in the forseeable
future. Gravitation and High-Energy Physics
Our best current theory of
gravity, Einstein's General Relativity, is incompatible with the Standard
Model of particle physics that successfully describes the other three forces
of nature (the electromagnetic, weak and strong nuclear forces). This impasse
has been called by Nobel Prizewinner Steven Weinberg the "one veritable
crisis" remaining in theoretical physics. Progress in such situations
usually depends on a combination of new theoretical ideas and experimental
strategies that probe at "weak spots" where existing limits and
predictions are unsure. In the case of gravity, two such spots involve spin and the universality of free fall,
also known as the Equivalence Principle. A review article I co-authored
with Paul Wesson on a class of extended theories of gravity known as Kaluza-Klein theories ranks 22nd among the "top-cited
articles of all time" in gravitation and cosmology with over 300
citations to date. I am especially intensely interested in the prospects for
testing such theories with experiments like Gravity Probe B (GP-B) and the
Satellite Test of the Equivalence Principle (STEP). Some recent papers:
I've written an online resource
for the public on this subject called "SPACETIME:
from the Greeks to Gravity Probe B". This website received over
500 "diggs" at digg.com and the
animations used in it (co-designed with Bob Kahn) won a bronze medal at the 29th
annual Telly Awards (2008). For students: I have
openings for two student projects in this area. One involves setting limits
on possible violations of the equivalence principle by solar-system bodies
using astronomical data on objects near stable Lagrange points, such as the
Trojan asteroids. The other involves characterizing the properties of
possible test materials to be used in modern-day versions of Galileo's Pisa
experiment. These projects would be appropriate for students with a solid
grounding in mathematics and classical physics plus some exposure to modern
physics. Cosmology and Astroparticle
Physics
The cosmic background radiation
that bathes our galaxy at all wavelengths carries a wealth of information, not
just about the visible universe, but also about the unseen dark matter and energy which are
believed to comprise 95% of the universe by weight. Dark energy is
particularly puzzling. Its existence appears to be forced on us by
observation, but makes little sense in the context of modern quantum field
theory (this is known for historical reasons as the
"cosmological-constant problem"). One way to reconcile the two
points of view is to allow dark-energy density to evolve with time. My PhD thesis on this topic was
completed just months before dark energy was detected by observational
cosmologists. The short
version (co-authored with Fred Cooperstock) is
an arXiv topcite 100+
article with nearly 200 citations to date. More recent work:
Dark matter is thought to make up
about 25% of the universe by density, as against 70% for dark energy. But
most of the leading candidates for dark matter are not perfectly dark. In theory,
they are unstable to annihilation or radiative
decay and therefore contribute to the cosmic background radiation at some
wavelength. The night sky thus serves as nature’s own dark-matter
detector. My work in this area has recently been summarized in a book
(co-authored with Paul Wesson) titled The Light/Dark Universe
(World Scientific, 2008). For
students: the research described in this book is ongoing, with multiple
opportunities for student involvement. Those with a historical or
philosophical bent might be drawn to the deep questions surrounding Olbers' Paradox (or why the sky is dark at night---not as
trivial as it may seem). Those whose interests lie in core subjects such as
electromagnetism, radiation transport and scattering theory will be
challenged to calculate exactly how much light should (or should not) be
reaching the Earth in various wavebands (the role of dust absorption is of
particular interest). Practically inclined students might use data on the
intensity of the night sky from detectors to draw inferences about everything
from the properties of stars and galaxies to the age of the universe. For
students interested in modern physics, I have a number of ongoing projects
regarding the contributions to the background light from decays and
annihilations of as-yet undetected particles and fields such as
"warm" dark-matter particles, super-heavy "cold" relics
from the big bang, and objects predicted by contemporary high-energy
unified-field theories. These would be accessible to students with some
upper-year background in astronomy, electromagnetism and/or modern physics. Other Topics
I’ve worked on other topics
including the evolution of
eyesight around the sun (see illustration at right), prospects for
observing quantum spacetime foam in laser interferometers, and the
lives of scientists such as Wolfgang
Priester (an early proponent of dark energy)
and Leopold Halpern
(the last assistant to both Schrodinger and Dirac, who developed a
generalization of General Relativity incorporating particle spin). I’m
currently collaborating with a Russian-speaking colleague to produce a
translation of some seminal papers from the 1950s by the fascinating
physicist Yu.
B. Rumer. For
students: you are welcome to contact me anytime with questions or
ideas for projects in theoretical, mathematical, philosophical, historical or
almost any other kind of physics or astronomy you wish to pursue. I look
forward to hearing from you! Last
Updated: 1/4/2011 |
