Natural Science Forum / Physics / Research / July 2006

The first two vanish into the back room to play a game of darts,
leaving the third to chat up the barmaid.  After emptying a stein, he
pulls a bit of ribbon from his pocket and entertains her with a trick
whereby he ties the ribbon to the handle, twists the stein around two

All laser pointers in the market use diode-lasers. What makes it so
difficult to make a pointer-sized free-electron laser?
Thanks,
Radium

I have some questions concerning density operators and the second
quantization formalism:
1. What is the density operator for a many-electron system in second
quantization?

What can you say about the QM Consistent Histories interpretation.
Do you agree with it or not and why?
http://quantum.phys.cmu.edu/CHS/quest.html
What is the relationship of consistent histories and standard

I have a 2D Riemann metric tensor with coordinates (x,y) in a half-plane
-Infinity < x < Infinity, y > 0. I can calculate the geodesics.
I am looking for suggestions on algorithms for visualizations
of the geometry. (Ideally, something I can implement in Mathematica).

For a jumping off point: http://tinyurl.com/l63rx
news:3DCC3733.8030802@hotmail.com
See also: Xu Tao: J. Phys. D: Appl. Phys. 29 (1996) 2932-2937
"The ball-bearing effect of diamond nanoparticles as an oil additive"

This month's Discover magazine has an article on MONDs and TeVeS.
There it describes both theories as being descriptive -- that is,
the law of universal gravitation or the Langrangian are modified
in a certain way when accelerations are low, but no real explanation

This came out of a philosophical discussion last night. It is probably
stupid from a physicist's point of view, so please forgive my ignorance.
Can a quantum theory of gravity (string theories?) live in a fractal
spacetime? In other words, the separation between two points in

Almost all physicists hold to the view that for any isolated pair of
particles, a and b which have masses, Ma < Mb, interacting elastically:
 Information has to continually travel (at speeds not exceeding c)
from one to the other

Please forgive my ignorance, but:
I just read that an electron can move from an inner orbit to an outer
orbit by absorbing kinetic energy through collisions. So why don't
gases just glow themselves down into a solid state, with collisions

As I understand it we can think of the Schwarzschild geometry
surrounding an isolated star as a static perturbation within an
expanding flat or near flat space-time. I would much appreciate
correction if I am wrong.

The Bohr-Sommerfeld rule allows approximating the spectra of integrable
systems in a quite accurate way, at least for high quantum numbers.
The most general formulation of the rule is as follows (I converted a
less

On a matter related to several other current threads here,  can anyone tell me
whether there are experiments that show that the time delay between the emission
and the (more or less remote) absorbtion of that exact same photon are
compatible with its speed being c ?

Reference postings: Unidentified object in a cloud chamber
I brightened up the video, grayscaled it and posted it in a higher quality
format.  I think this shows that the movement of the glow is correlated to
the condensation trails (i.e. trails form, end or change direction at ...

Hello, spr.
I took my Lightning Thunderbolt recumbent equipped with Wilderness EV
600 W capacity front hub in parallel with a bank of (series wired)
ultracapitors (8 x Maxwell PC 2500 @ 2700 F each) and a voltmeter for a