Natural Science Forum / Physics / Research / October 2004

Does anybody know how to compute material parameters if we have
wave function (density of probability) of molecule from with this
material is build. How to compute density, melting temperature or
dielectric constant. I know about Brillouin function in periodic

Everybody has presumably already noticed
http://www.arxiv.org/abs/hep-th/0409182, where Robert Helling and
Giuseppe Policastro compare Fock and LQG quantization of a string.
In particular, they notice that one can do LQG quantization of

Please do not be shocked.
I would quite like to read up on 4-vectors and if possible their care
and feeding with respect to simple mechanics and the faraday tensor.
I am completely uninterested in relating this back to 'conventional

Lubos,
I was looking at your paper with Neitzke, hep-th/0301173.  I am
reading 2.4 in the paper and have probably a very basic question.  You
say it is convenient to choose the branch such that n=0.  Other than

in math.NT/0409306, Connes and Marcolli investigate the occurence of
'the action of a certain universal "Motivic Galois Group" on the set
of physical theories' and wrote:
"...these facts altogether indicate that the divergences of Quantum

I noticed that in QFT there is two kinds of commutators in QFT, some
commutators like [x,p]=i or [phi, phi]=0 give you a number, and some
commutators give you another operator like [J_i, J_j] = c_ijk J_k, I
often feel perplexed, when should I expect a number and when should I

I am thinking about classical-quantum correspondence and the decoherence
theory. I think that any theory that shows how classical emerges from
the quantum must explain the following:
1) Why are objects around us not in a superposition of states?

I was reading the Black Hole FAQ. I am having a problem with the
"vaccum fluctuation"  explanation of black hole evaporation.
"If a particle + anti-particle pair is created at the horizon, one of
them escapes away and other falls in. So it looks like the BH has just

I was thinking about magnetic monopoles, and I thought there
might be some trouble with angular momentum.
If you calculate the angular momentum density rXEXB for
a point charge (e) at (0,0,d/2) and a magnetic monopole

In the path integral formulation of QFT for bosons,
the canonical commutations relations are not
even mentioned. (Ref: Peskin & Schroeder, ch9).
For fermions, P&S say that we must introduce

I was reading a few more papers on arxiv.org:
http://www.arxiv.org/abs/quant-ph/0003083
http://www.arxiv.org/abs/quant-ph/0006079
In the first paper Johan Hansson proposes that perhaps the

I'm looking for a document or a picture that represents the most
important 20th century physics theories with their interdependencies.
E.g. quantum electrodynamics would have two dependencies -
nonrelativistic quantum mechanics and SR; loop quantum gravity

The fundamental theory of Wigner says that any symmetry transformation
can be represented on the Hilbert space of physical state by an
operator that is linear and unitary(except the weird time reversal
which is anti-unitary and anti-linear), so the unitary operators play

First, I'm curious how one can explain the EPR paradox in relativistic
QFT, since one sets (as I understand it, anyway) [q1(x1),q2(x2)]=0
when x1 and x2 are spacelike related points and q1 and q2 are
arbitrary operators.  This seems to destroy the possibility of having

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