Recent content by Sum Guy

Hello everyone, I am currently trying to understand how we can use feynman diagrams to estimate the matrix element of a process to be used in fermi's golden rule so that we can estimate decay rates. I am trying to learn by going through solved examples, but I am struggling to follow the logic...

Please could you explain which of the processes above are irreversible and why?

All of the processes are reversible in theory though, no?

"All Reversible Heat Engines have same efficiency when operating between the same two temperature reservoirs." See: http://aether.lbl.gov/www/classes/p10/heat-engine.html

Homework Statement I have a question regarding heat engines that cropped up whilst I was doing a practice question. I will summarise the results I obtained for the previous parts of the question so as to save your time. The highlighted parts of the image are where I am having some issues. I...

My reasoning was as follows: $$Z_{in 2} = Z_{2} \times \frac{Zcos(kl) + iZ_{2}sin(kl)}{Z_{2}cos(kl) + iZsin(kl)}$$ where ##Z = 0## (?) Giving $$Z_{in 2} = Z_{2} \times \frac{iZ_{2}sin(kl)}{Z_{2}cos(kl)} = Z_{2}itan(kl)$$ What is wrong here?

Homework Statement I am having problems with the second part of the question - proving that the relationship given is true. Homework Equations See question. The Attempt at a Solution Firstly, consider a single pair of transmission lines with characteristic impedances ##Z_{1}## and ##Z_{2}##...

Considering how Heisenberg's uncertainty principle is applied to a top-hat wave function: This hyperphysics page shows how you can go about estimating the minimum kinetic energy of a particle in a 1,2,3-D box: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/uncer2.html You can also...

I was following this derivation of the solution to the Laplacian in spherical polars. I was wondering where the two equations ##\lambda_{1} + \lambda_{2} = -1## and ##\lambda_{1}\lambda_{2} = -\lambda## come from? Thanks.

Thank you for this - it's a nice thought. Is there any way you could apply this mode of thinking to the situation where ##\psi = R(r)Y(\theta, \phi) = R(r)cos(\theta)## say?

Suppose we have an electron in a hydrogen atom that satisfies the time-independent Schrödinger equation: $$-\frac{\hbar ^{2}}{2m}\nabla ^{2}\psi - \frac{e^{2}}{4\pi \epsilon_{0}r}\psi = E\psi$$ How can it be that the Hamiltonian is spherically-symmetric when the energy eigenstate isn't? I was...

This is something I found in a pdf online where it simply asserted what the eigenfrequencies were... and not how to find them.

If I have a system where the following is found to describe the motion of three particles: The normal modes of the system are given by the following eigenvectors: $$(1,0,-1), (1,1,1), (1,-2,1)$$ How can I find the corresponding eigenfrequencies? It should be simple... What am I missing?

I haven't solved the tapered case? I don't know how to..?

Please could you give me a clue as to what integral I would have to do? I'm struggling to see how I am meant to take account of the tapering in an integral amperean loop...?