Natural Science Forum / Physics / Research / November 2006

Once again, the ghost of a preferred frame of reference in our
universe arises. All those maps of Cosmic Microwave Background
Radiation (CMB) provided by WMAP show non systematic anomalies.
In particular, the quadrupole and octupole (l = 3) modes appear

Why can we add masses together and get a mass? This question may seem
stupid, but we can't do the same with time: we need to add a time and a
*duration* to get another time.
It seems to me like adding masses depends on various assumptions, like

Also available as http://math.ucr.edu/home/baez/week241.html
November 18, 2006
This Week's Finds in Mathematical Physics (Week 241)
John Baez

What is the highest-frequency sound that can exist in Earth's
atmosphere?
AFAIK, there is no limit, but I would like some clarification.
Is it possible for a pure-sine-wave tone of 140 dB, 10^10,000 Hz [i.e.

Hello group, at page 629 of Penroses Book road to reality, Penrose
claims that one can break down the dirac equation to two "ingredients"
alpha_a and alpha_b : In the references Penrose says that he is not gone
to the detail here ,how the decomposition of the dirac equation that he

Roger Shawyer, a British engineer who claims he can generate thrust from
a closed cavity full of microwaves, will be giving a free public lecture
on his invention at Imperial College London, on Thursday 23 November at 6
pm.

There are two distinct methods of renormalization: A) BPHZ
renormalization, without any specific regularization. B) Counterterm
renormalization, usually with the help of dimensional regularization.
The second method is used in most QFT books to prove the

21-NOV-2006
In Guth's original paper on inflation, the mechanism for the
exponential expansion in the early universe was given as a supposition
that supercooling continued until the temperature was many orders of

In four dimension, the Pontryagin term is a total divergence, hence it
is topological. It is called the theta term when it's included in
QCD.
There are lots of references on quantizing topological field theories.

I've always been very uncomfortable about the QM spooky effects, and
have often been quick to point out any potential loopholes in any
experimental "proof".  I've previously attempted to at least consider
alternative explanations.  I can't stomach multiple worlds.  Cramer's

What transformations on a bipartite state, rho preserve the
entanglement? SU(2)XSU(2) does - and this would have 6 parameters.
Also, if the eigenvalues are w,x,y,z subject to the condition that
their sum is 1 and another condition from the entanglement(some value

In SO(8) there is a symmetry between the three representations (vector,
left-spinor & right-spinor).  Is there any simple systematic way to
find out what the decomposition of, say (8v x 8c) is?  Some of them are
easy like (8v x 8v), but how do you do itin general?

Dirac's belt trick models the behaviour of spin 1/2 particles.
When turning the end of the belt (the particle)  by 4 pi,
the belt can be untwisted even while keeping the particle fixed.
Is there an analogous trick for spin 3/2? It seems that this would

Given a massless particle (rest mass = 0), other than a photon or
graviton, what would be the relativistic explanation for why it can
travel faster than c?  What aspect of electromagnetic radiation make
its speed of propagation in free space an upper bound on speed?  I

Suppose we have a drum whose membrane is a connected subset M of R^2 with
a piecewise smooth boundary, and we assume that the displacement of the
membrane f(x,y,t) obeys a lossless, dispersionless wave equation:
 lap f = (1/v^2) @^2 f / @t^2