Recent content by johnsmi

My question was less about IFF and more about reverse engineering. I would like to be able to look at an antenna and understand for example that if the antenna is a wire antenna then it is meant to be used for... as opposed to ring antennas, dish antennas or horn antennas. And what can I tell...

Hi, I havn't posted for quite some time yet I have been reading through from time to time. I would like to ask about Radars. I wish to be able to look at a radar antena and be able to say as possible. Such as frequency ranges from the antenna size etc... Does the size of the 'Ball' in which...

If I may ask, what kind of project would a math grad. student be working on? (Still, yet unsuccessfuly, trying to find the beauty in math)

First of all I don't know if you noticed but the post is from two and a half years ago (quite some time). Now, if you want to know about the sign function an easy way to think of it is a funtion which is negative one on the left hand side of the axis and positive otherwise. In other words...

Hi, I have come across a sentance in an article which I do not quite understand. H1 is just a perturbation Hamiltonian. Why will spin flips only occur at the Fermi level? Thank you

Can I assume that a spinor (spin state that depends on location) state and an eigenstate of momentum (which also depends on location) are in separate Hilbert spaces or does the momentum operator act on the spinor as well?

thank you, the identity map was a stupid mistake of me But after having a better look in Cohen-Tannoudji I understood that qbert made a slite typo mistake and it should be <m \otimes \mu| H |n \otimes \nu> = <m \otimes \mu| (H_1 \otimes \text{id}_2) |n \otimes \nu> + <m \otimes \mu|...

Your unswer seems to be very usefull since I did find in a related article something like this: <\uparrow (\phi)| \otimes <\phi| \frac{\Pi^2}{2M} |\phi '> \otimes |\uparrow (\phi ')> = <\phi| \frac{Q^2} {2M} |\phi '> \\ where\ Q=\Pi -const. I think I am beginning to understand what...

Wow, thank you for your detailed post now all I need to do is understand it. I think it will take me some time to properly understand it. Thank you very much!

Thank you for you reply but it doesn't quite fit with something: https://www.physicsforums.com/showthread.php?t=416185" is a post I posted with all the details of the question and as you can see it doesn't seem to apply (does it?)

Hi, I'm trying to understand something: Supposing I have two states: |\uparrow> which is an eigen state of H1 and \psi which is the space rep. of an eigen state of H2 Now, as far as I understand |\uparrow> \otimes \psi will be an eigen state of H1 \otimes H2 (is that true or is it the...

Homework Statement Hi, I need to integrate this: \int(J0(r))2rdr between 0<r<a It is for calculating the energy of a nondiffracting beam inside a radius of a. (the r is because of the jacobian in polar coordinates) The Attempt at a Solution I saw somewhere that said the integral was a...

Homework Statement Hi, I would like to know what is the right way to write continuous deltas standing in a circle of radius a? Homework Equations The Attempt at a Solution I am not sure weather it's δ(r-a) or is it δ(r-a)/|r-a| Thank you

Thank you for your reply. By the way it was mentioned in the article that h bar was taken to be 1

I'm not sure but I'll try. After experimenting (don't worry no car crashing) I think the difference originates from the fact that the crane as holding the car not above the mass centre and therefore the car started falling in an angle. my experiment was as follows: Take a pen (not Parker...