Recent content by Dixanadu

Hi guys, So just wondering - the fact that the force is always the negative derivative of potential with respect to distance: F=-\dfrac{\partial V}{\partial x} Where does this come from and does it have a name or something? like a theorem perhaps? Thanks!

Hey everyone... so I understand that an alpha particle, being a helium nucleus, is quite a large particle compared to, for example, a beta particle. Due to this, it will encounter a lot more collisions and impart its momentum to other particles of air at a much more rapid rate. Is there...

Okay, thank you I think I get it. Also, do the light rays bend due to refraction?

Hey guys, Can someone give a basic explanation of why a camera can take a picture even if half of its lens is covered up? Thanks guys...

Hi everyone, So one of my students has asked me a question which I'm not sure how to answer. The question is: Why does the wire that supplies current to the filament lamp in a light bulb not heat up, even though the filament itself does? Please let me know your thoughts! Thank you :)

Hey guys, So here's the issue I'm faced with. I need to integrate the following by parts (twice): \int d^{3}y\, e^{ik(\hat{n}_{0}-\hat{n})\cdot\vec{y}}\left[ \nabla\times\nabla\times\hat{\epsilon}_{0} \right] And I have absolutely no clue how to approach this. The result I'm meant to reach is...

Hey guys, So I'm reading a textbook which has the following equation: \dot{X}^{-}\pm X^{-\prime}=\dfrac{1}{4\alpha' p^{+}}\left( \dot{X}^{I}\pm X^{I\prime} \right)^{2}. Please note that the +,-,I are indices. Then the author says: \dot{X}^{-}= \dfrac{1}{4\alpha' p^{+}}\left(...

Okay guys so I the lagrangian \mathcal{L}=\dfrac{1}{2}\left( \partial_{\mu}\phi\partial^{\mu}\phi-m^{2}\phi^{2} \right)+\dfrac{\lambda}{4!}:\phi(x)^{4}: where \phi(x) is a real scalar field. I want to know how you can draw the self-energy diagrams at order \lambda and \lambda^{2} for a 2 => 2...

Hey guys, So I have a question about the gauge invariance of the weak field approximation. So if I write the approximation as \Box h^{\mu\nu} -\partial_{\alpha}(\partial^{\mu}h^{\nu\alpha}+\partial^{\nu}h^{\mu\alpha})+\partial^{\mu}\partial^{\nu}h=0 then this is invariant under the gauge...

Yes doctor that solves my problem. The terms now cancel if I have a factor of 4 in front of one of them due to the trace of the delta tensor in spacetime. You saved the day once more doctor, you should consider becoming a superhero :D thank you!

is it 4..?

I think it's easier if I just tell you a few terms. So in each line there is an example of a product of terms:

That's fine there is a typo...there is a cdot somewhere it shouldn't be in the first term. But mu isn't = nu and there is only one term where the two etas are being contracted. If that term goes to 0 I get

OMG so those terms vanish? :O

Here it is... Btw is \eta^{\mu\nu}\eta_{\mu\nu}=1 or -1 lol XD I've assumed its +1