# Tag Info

### Muon pair production

You can answer this question by drawing the diagrams for the Mandelstam variables. Below, from Wikipedia, with time increasing to the right: In the s-channel, the intermediate trajectory is timelike, ...

### Transfer of momentum at quantum level

Each scattering process conserves momentum individually -- which would result in a bunch of processes conserving momentum as a whole as well. For example, a typical interaction in which two electrons ...

### Imaginary part of IR divergence in gravitational S-matrix

I will try to give you some guidelines that will (hopefully) help you understand some key differences between Weinberg's work and the authors' in the article you cite (despite not having a complete ...
1 vote
Accepted

### Relation between Rayleigh scattering intensity and Poynting vector of an oscillating dipole

The formula you give for Rayleigh scattering is for unpolarized light, consisting of equal amounts of two perpendicular polarisation states. These two states excite two perpendicular oscillations in ...
1 vote
Accepted

### Solving Schrodinger Equation for scattering off a periodic potential

In my scenario however, the cystal is finite in the z dimension, and so the Bloch theorem won't strictly hold. This is wrong. Bloch theorem holds in any periodic medium, including finite ones. In ...
1 vote
Accepted

### On relativistic kinematics of particle accelerators

The invariant mass is equal to the total energy in the center-of-momentum reference frame. This does not mean that the center-of-momentum frame must coincide with the lab frame. Instead it means that ...
1 vote

### EM wave direction after Rayleigh scattering

The question boils down to: What are the EM fields associated with an osscilating dipole? $$\rho = -\vec{P}\cdot \nabla \delta^3(r)$$ $$\vec{J} = \frac{d\vec{P}}{dt}\delta^3(r)$$ If your ...
1 vote

### EM wave direction after Rayleigh scattering

Your first diagram is a graph using polar coordinates of the intensity of scattered light $r$ as a function of the scattering angle $\theta$ as defined in the second diagram. So the intensity os the ...
1 vote
Accepted

### EM wave direction after Rayleigh scattering

The second image is a reasonable picture. The first could be possible but would need qualification and explanation. Rayleigh scattering occurs when the electric dipole moment of the molecule is made ...
1 vote

### EM wave direction after Rayleigh scattering

A molecule excited by light will oscillate in the direction of the electric field. It becomes an oscillating dipole, which has a donut-shaped emission pattern (perhaps hinted by your final image). ...
1 vote
Accepted

### I'd like to understand Rayleigh scattering

Amount of energy per area only makes sense if your light is propagating along a certain direction. After scattering this is explicitly not the case. So some of the light makes it to you on Earth, some ...
1 vote
Accepted

### On physical interpretation of Mandelstam variables

As you said they name is totally related with the diagram, since the i-variable is simple the sum (+) of the momentum that go to an annihilation minus (-) the momentum that are created from a vertex ...

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