I have been told that L and P^2 do not commute, but I don't see why. It seems like the commutator should be zero.
\left[ \vec{L} , P^2 \right] = \left[ L^k , P_i P_i \right]
= \left[ L_k , P_i \right] P_i - P_i \left[ L_k , P_i \right]
= \left( - i \hbar \epsilon_{i}^{km} P_m \right)...
I'm finding the percent error in a S.R. problem and getting a really small number. How can I find the exact percentage? This is the result that needs to be simplified:
6.7x10^(-16) / (1 + 6.7x10^(-16))
If I do an order of magnitude approximation, then the bottom becomes 1, but that will...
I'm trying to work through getting the Riemann-Christoffel tensor using covariant differentiation and I don't see where two terms cancel. I have the correct result, plus these two terms:
d/dx^(sigma) *{alpha nu, tau}*A^(alpha)
and
d/dx^(nu) *{alpha sigma, tau}*A^(alpha)
Sorry, I couldn't...
I have two options right now and I would like to hear what you would do in this situation.
I don't have any research experience to put on a grad school application. If I take the GRE this fall, I will just be starting QM, so I probably won't be able to solve many of the QM questions on the...
I have to show that a generic vector can be decomposed into an irrotational and solenoidal component:
V(r) = -Grad[phi(r)] + Curl[A(r)]
I'm not sure how to start. Do I need to take the curl or div of V and use a vector identity? Any help would be greatly appreciated!
I don't know if this belongs in Philosophy or Skepticism/Debunking...
I seen the section of the paper with the daily horoscopes and got to wondering: How would physics change if one of these Miss Cleo or Edgar Cayce type people were real (capable of consistently and accurately stating what...
"Physicist" title
I'm not sure what section to post this in, so I guess this one will have to do.
I was recently told by an engineer that they have the title "Engineer" with a bachelor degree. I have always assumed the title "Physicist" was reserved for someone with a phd. But that got me to...
I'm not understanding something here. Maxwell's wave equation is:
Laplacian of E = (1/c^2) * second partial of E
(sorry, I don't know how to write symbols)
But the second partial derivative is the Laplacian. So how can you scale the laplacian of E by a number and get the laplacian of E as...
Which do you think would be better for getting into a theoretical physics program:
-- a 2.5 cumulative gpa with a 3.5 physics gpa
or
-- a 3.0 gpa, both cumulative and physics
Also, if your gpa is around 3.0 (+- 0.2), what are your chances of actually getting into a phd program?
The problem:
Find the value of dz/dx at the point (1,1,1) if the equation xy+z3x-2yz=0 defines z as a function of the two independent variables x and y and the partial derivative exists.
I don't know how to approach the z3x part. I thought you would use the product rule and get 3(dz/dx)2x +...
I am working through Einstein's "On the Electrodynamics of Moving Bodies", and I can't figure out why we are using c instead of a random constant velocity. It seems to me that c is an arbitrary value for the argument. I'm sure there is an explanation... I just can't think of it. Can anyone clear...
I am finishing my junior year as a physics major, and I've heard that alot of people get a minor in math or something like that. I plan to start grad school immediately after finishing my undergrad. My question is, what is the purpose of getting a minor? Does it look good on a grad school app...
Is there a way to find the distance between atoms? For example, if you have a pure gold film... how can you find out how far the gold atoms are spaced?