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user7077252
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7 votes
1 answer
647 views

Finding the amplitude for the pair production $\gamma(p_1) + \gamma (p_2) \to e^- (p_3) + e^+ (p_4)$

6 votes
2 answers
376 views

How are annihilation/creation operators used to reach an external state of $|0 \rangle$ in an $S$-matrix?

4 votes
3 answers
236 views

Can a fibre preserve the shape of the light being transported through it?

4 votes
2 answers
310 views

Deriving the number of loops and number of lines meeting at a vertex in a diagram

4 votes
2 answers
96 views

What are ordinary mass-terms (of neutrinos)?

4 votes
1 answer
406 views

How is the helicity fixed by little group scaling?

4 votes
1 answer
293 views

Understanding the proof of the "Photon-Decoupling Identity" for colour-ordered Yang-Mills amplitudes

3 votes
2 answers
286 views

Why does the observation of $Z$-boson decay imply active neutrinos to be heavy?

3 votes
1 answer
334 views

What is the mathematical meaning of locality?

3 votes
1 answer
135 views

I do not understand this bra-ket notation equality for BCFW recursion

3 votes
2 answers
402 views

What is the general form of the Friedmann-Robertson-Walker metric in 4D?

3 votes
2 answers
1k views

Does the Thomas-Fermi screening length formula only apply to metals?

2 votes
1 answer
298 views

What are the best resources for Crystallography?

2 votes
1 answer
85 views

What is a neutrino state if not a particle?

2 votes
0 answers
42 views

Why would the damping factor of neutrino oscillations be negligible?

2 votes
2 answers
1k views

How do I obtain the Dirac equation from the Euler-Lagrange equation?

2 votes
0 answers
202 views

What is the meaning of a Fermi blocking effect?

2 votes
0 answers
43 views

Is this formula for the Hubble expansion rate always correct?

2 votes
1 answer
209 views

Glashow-Weinberg-Salam (GWS) Theory for Gauge Boson Masses

2 votes
2 answers
205 views

What does the colons in $:\hat{P}:$ mean?

2 votes
1 answer
62 views

Show equation equivalent in RG of 1d Ising Model

2 votes
1 answer
793 views

What does it mean to extremise the action function?

2 votes
1 answer
57 views

What causes neutrinos to be weakly coupled?

2 votes
1 answer
98 views

Decomposing the $\mathcal{N} = 4$ massless graviton supermultiplet

2 votes
2 answers
248 views

How can the Euler-Lagrangian equation be applied to the Schroedinger Lagrangian of several fields?

2 votes
0 answers
102 views

How is ECR (Electron Counting Rule) done in a structure?

2 votes
1 answer
784 views

Why does water easily absorb THz radiation?

1 vote
0 answers
110 views

What are the "frustrated rotations" of molecules?

1 vote
2 answers
147 views

Do identical, equally spaced lenses possess the same magnification, or does it depend on the sample's distance?

1 vote
2 answers
173 views

What is the "Doppler mismatch"?