Recent content by 1Kris

I have two related questions to ask relating to statements found in introductory particle physics textbooks. The first is that the "Dirac equation predicts fermions/anti-fermions have opposite intrinsic parity". I have attempted to verify this by applying the parity transformation to free...

Thanks very much. You've pulled me out of that horrible mess of confusion! I had briefly thought of the condition you gave but I dismissed them before I figured out the consequences because I didn't think it was either the Laue condition or Bragg's law. Thanks again.

Thanks for the reply. The vectors k, k' and K make a triangle because of the vector addition relating them. To minimise k, surely the triangle would be flattened such that k and k' run parallel to K. This gives k=k'=K/2. and we know λ=2\pi/k (11)...

Homework Statement A two-dimensional rectangular crystal has a unit cell with sides a 6.28Å and b 3.14Å. A beam of monochromatic neutrons of wavelength 5.0 Å is used to examine the crystal. Using either the Laue condition for diffraction or Bragg's Law, determine whether it would be...

Thanks for your responses so far. Regarding rules, I'm not sure how to specify them so I'll just give you my motivation for wanting such a list. I have decided to give myself a series of small physics projects that involve learning how the famous problems in physics were solved and hence...

Hi, I'm trying to make a list of Physics problems that were "the problem" of their day. I want things like the precession of the perihelion of Mercury or the anomalous magnetic moment of the electron. I'd appreciate it if you could name and briefly describe any interesting problems that were...

Haha thanks for that, why infuriating?

In the Feynman Lectures on Physics, Volume 3, Feynman uses a an approximation of treating systems as two state systems. Is this the same as perturbation theory, or is it a different method?

In my quest to learn quantum mechanics I've become a little confused and I have a question. It is "In The Feynman Lectures on Physics Volume 3, is most of the work, eg. ammonia molecule done using perturbation theory or is this method something else, not perturbation theory?" I started to...

If I had a hamiltonian of the form iA(p + c), where A is a constant matrix, p the momentum operator and c an ordinary constant how do I find the time rate of change of the expectation momentum value? I've tried using Ehrenfest's theorem but I don't understand whether in [p,H], I should treat p...

So roughly speaking are we saying that each value of a function can be thought of as one of infinitely many components of a vector?

Thanks for the speedy and clear response. Does that suggest that any linear operator A can be written as a matrix and if so is there a general method?

Hi, I've been reading a couple of different books on quantum mechanics and have come a mathematical difficulty. I understand that the Hamiltonian is an operator but in some books, it represented as a matrix and in others as a differential operator? How can they both be equivalent approaches...

Well think in terms of force of the condition that causes this equilibrium. Write down the equation for the two forces involved and the rest is just simple algebra (then a calculation when you stick the numbers in).

What's the question asking for?