Recent content by masudr

Are you sure it wasn't \sqrt{7 \alpha}

Virtual particles are not bound by the relation E^2 = p^2 + m^2. This is not a problem however, as spacelike separated field operators have a commutator of zero, and therefore causality is not violated in quantum field theory.

Imagine the sun wasn't rotating, and let's assume it is electrically neutral, for now. Then yes, the spacetime surrounding the sun is identical to the spacetime region outside a black hole. To that extent yes, what's going on inside doesn't really matter. But then the mass of a Higgs is far...

You're saying that any single particle excitation of a chargeless, massive scalar field is a chargeless, ang. mom. zero black hole. I don't follow the logic. To get a (nonspinning, uncharged) black, you need to squeeze some mass into a sphere with radius smaller than the Schwarzschild radius...

Neat! I'm going to transcribe your LaTeX with the partial deriv. signs put in ('cos my brain can't read it otherwise) and ask you about the final step: \frac{\partial g^{\mu\nu}}{\partial g_{\lambda\sigma}} = \frac{\partial}{\partial g_{\lambda\sigma}}...

I think closure was originally accepted as a proper axiom, but it is kinda self-evident in the definition of the binary operation and its domain and range. The reason for specifying closure is because it is an axiom that can be overlooked when checking to see if an algebraic system is a group or...

It's called that because it's kind of half way to being a group. Think of it like this: 1. You have a set S with a binary operation S x S -> S, then we call that a magma. 2. Make that operation associative, then we call it a semigroup. 3. Include an identity element of the operation within...

You can't stop a laser unless you have something that is opaque to the frequency the laser is operating at.

I'm not discussing the practicality of the method (just yet), just investigating if the method would work or not. That's quite correct, but if the electron is on the other side as it were (or, I should say, in all the systems of the ensemble of systems where the electron is on the other...

What if the parameter \xi in my description above was 5 orders of magnitude smaller than the Bohr radius? The electrical neutrality of atoms wouldn't matter as we'd push back the electrons before the protons could even feel the field.

Couldn't we have an electric vector field such as \vec{E}(x,y,z) = -E_0 \vec{j} e^{-y/\xi} where E_0 is a large positive number, and \xi indicates how "thick" the repulsive wall is. This would work because all the negatively charged electrons on the outer shell of all normal objects...

I don't personally see a problem with Fredrik's statement that there's nothing more general about the transformation of coordinates as well as fields, since we can combine the two transformations. I think the real point of separating is to clearly see the difference between internal and...

We have some action that is the integral of the Lagrangian over spacetime. We postulate that all the physics is contained in the action, and so any transformation that leaves the action invariant (not the Lagrangian - it is more general to consider the action, since that is the physical thing)...

SO(3) is the group of transformations on R^3 which preserves the bilinear form x_1^2 + x_2^2 + x_3^2 and does not perform an inversion on the space. SO(3,1) is the group which preserves x_0^2 - x_1^2 - x_2^2 - x_3^2, i.e. the Lorentz invariant form. SO(n,1) is the obvious generalization of...

The 4-component Dirac spinor transforms under the (1/2, 1/2) representation of the Poincaré algebra. This is essentially 2 spin-1/2 particles, i.e. the left handed and right handed Weyl spinors. The scalar Klein-Gordon field transforms under the (0, 0) rep., and so describes a spin-0 particle.