Recent content by Adam Lewis

Well, that would get you the minus sign. But I had thought the fact the spins were anti-parallel to be already encoded by the singlet state. It seems odd to me that you should have to insert this information again via the operator. Maybe I'm misunderstanding how \vec{\sigma} is supposed to work?

Reiterating PeterDonis' point, 13.7 billion years is the time since the singularity in the rest frame of a special class of "comoving" observers. Comoving observers use coordinates which "factor out" cosmological expansion so that galaxies participating in the expansion are always at the same...

Hello, I am trying to reproduce Bell's calculation for the expectation value of paired spin measurements on particles in the singlet state. For unit vectors \hat{a} and \hat{b} we want to calculate P(a,b)=<\psi|(\hat{a}\cdot\vec{\sigma})(\hat{b} \cdot \vec{\sigma})|\psi> where...

Hi, I mean, a spherical shell (the surface of a ball). I need e.g. parametric equations or something for the resulting surface. -Adam

Hi, A bit more information might be helpful. Is the bar a continuous line of charge, or two point charges separated by 3 metres. In the former case you need to integrate along the bar using for example Coulomb's law. In the latter case you just need to sum the forces from the two charges.

Hello, I have a probability density which in its rest frame is evenly painted upon a 2-sphere. I need to figure out how that density transforms under a Lorentz boost. Heuristically, this will consist of boosting the 2-sphere to obtain an ellipsoid of some sort, then doing a parallel...

Hi Perp Student, Yes, that is correct. The term "Rindler space" is actually a bit inaccurate since the spacetime being described is just the Minkowski vacuum - "Rindler coordinates" would be better. Geodesics in Rinder coordinates are indeed the same as those of Minkowski space in the...

Suppose an electron crosses worldlines with me such our relative velocities v are a substantial fraction of that of light. Say the electron's spin is in some state \mid\psi\rangle; for example the doublet state. I would like to know, or read references that describe how to calculate, what...

That's interesting. Do you know what's supposed to happen for non-inertial observers in spacetimes with no timelike Killing vector? What does it mean more formally to have 'multiple possible notions of time translations'? I mean, the stress-energy tensor should be zero since both of these are...

I mean, the energy in the fuel should curve the spacetime, and that the situation being described is therefore not a solution to the field equations. By energy I mean the whole stress-energy tensor, which admittedly is not standard usage. (this was posted before PeterDonis' reply)

I have a question about the Unruh effect. For the spacetime to be flat, it must contain no energy. But the Rindler observer is supposed to be eternally accelerating, which would require infinite energy. Is there an obvious resolution to this apparent contradiction?

Hi again, Thanks a bundle. I guess the dot when c is pulled out represents scalar multiplication? The integral without c is of course a scalar, which was confusing me. Thanks!

Homework Statement Prove \int_{V}\nabla\ T d\tau\ = \oint_{S}Td\vec{a} Homework Equations Divergence theorem: \int_{V}(\nabla\bullet\vec{A})d\tau\ = \oint_{S}\vec{A}\bullet\ d\vec{a} The Attempt at a Solution By using the divergence theorem with the product rule for...

Hi, I brought this up in physics class a while ago but didn't get a very satisfactory response... A train moving at some ridiculous velocity near that of light is watched by two observers. The first is a circa 1885 villain who twiddles his moustache nefariously from aboard the train (and in its...