Natural Science Forum / Physics / Research / October 2007

 I am studying QFT and wanna complete the fish diagram calculation in
the Minkowski space   with i-epsilon prescription to see the
"imaginary part."
 I know the roughly procedures, i.e., use Feynman formula to rewrite

Last night I picked up a book regarding the theory of gearing.  That is,
a mathematical formalism for the action of gear mechanisms was
developed.  The author introduced an formalism that at first seemed very
odd, but upon reflection seems quite elegant.  I am wondering if this

I tried this on sci.physics, but I'm hoping for a clearer answer
here.
Numerous textbooks (including Feynman's Lectures and the Berkeley
Physics series) make statements along the lines of "Maxwell's

I am trying to understand how an electrostatic field inside a cavity
in a conductor is shielded from a probe on the outside.  For
simplicity, we could even work with a hollow metal sphere. Lets say we
had a bunch of positive charges inside, on a insulated stand, and the

I'm playing with Ricci flow at the moment. Ricci flow is quite a buzzy
word these days, since it was used recently to prove the Poincarre
conjecture. Since the Poincarre conjecture, as one of the 7 Clay
institute millenium problems, was famously difficult to prove, you'd

I used Cavendish's observations (Experiment IV of August 12, 1797) to
compute a value for G. I believe that this was not done in modern
times. G is usually computed from the mean density of the earth
computed by Cavendish using the formula N^2/(a constant) B. But I am

Since going to and returning from Budapest, a long time ago, I've been
haunted by the ghost of von Neumann. Though it's probably not widely
known, he was a major pioneer in BOTH Computer Science and fundamental
Physics, establishing a foundation in the latter based on the primary

or is it just very poorly written by a reporter who doesn't know what
he/she is writing about.
http://www.smh.com.au/news/World/Swiss-to-use-encryption-voting-method/2007/10/1
3/1191696216022.html
i'm curious as to what the real physikers think about it.

What is the rough argument that spin network states solve constraints
in Hamiltonian formulation of General Relativity? I tried to look at
several papers, but I don't understand the main point.
Thanks in advance,

I just noticed what seems to be an inconsistancy in the use of the
term "source" as in "source free". Please straighten me out.
In the case of a heat flow in a medium, we have a heat flow vector h= -
k grad T and we have, in case of no injection, production or

I have discovered a simple and amazing result, a surprising
consequence of the maximum entropy principle, and would like to know
if it is true or not. Here it is:
Mathematically, from the set of constraints (p_i reads p with indice

I've always thought that, were it possible for biology to harness
ionizing radiation for energy, some organism would already have done
so.  The ground contains vast fungal and bacterial communities, but
also contains "light sources" in the form of uranium ore deposits.

is there a nice and simple way to see how worldsheet weyl anomaly
translates into target spacetime lorentz anomaly, in bosonic string
theory?

How the electron, photon detectors in double slit experiments work?
Thanks.

"Relativity without tears" can be found here
http://uk.arxiv.org/abs/0708.0929
I'll appreciate corrections of English. Other comments are also
welcomed.