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...
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 deal. Consider the Lagrangian
\mathcal{L}=\bar{\psi}(i\gamma^{\mu}\partial_{\mu}-m)\psi
where \bar{\psi}=\psi^{\dagger}\gamma^{0} .
I need to find the Hamiltonian density from this, using
\mathcal{H}=\pi_{i}(\partial_{0}\psi_{i})-\mathcal{L}
So I get the following...
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!
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