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 I've been working too hard,...

I'm interested in the prehistory of the history of relativity. In this history the nature of light and the ether comes in. One phenomenon that was debated in this context was...

Hi: 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...

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...

In article , Marc Millis wrote: Thanks for asking for the clarification. They way that I...

In article , "Spud" wrote: Greg Egan wrote: As for how they get measurable thrusts,...

There are two distinct methods of renormalization: A) BPHZ renormalization, without any specific regularization. B) Counterterm renormalization, usually with the help of...

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...

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...

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...

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...

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...

In article , Marc Millis wrote: Thanks for pointing us to this short article. One particular...

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...

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...

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...

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...

Suppose a self-adjoint operator F on a Hilbert space has discrete eigenvalues m_1 , m_2, m_3, etc. It is sometimes possible to find a "creation operator" C such that if ...

I wrote: But the overall effect of the total, 2pi rotation would just be ^^^ Sorry, I meant 4pi to restore...

I am interested in calculating the vertical wavenumber from an acoustic field radiated by a sonar transducer. Suppose that I know the pressure p at every point on a 2-D...