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HNQ
1:00 AM
1
Q: How to determine the sign of coupling constant in quantum field theory?

feng linExperimentally, we determine the value of the coupling constant by measuring the scattering cross-section and compare it with the results calculated by the scattering amplitude. However, in the expression of the scattering cross-section, it is proportional to the square of scattering amplitude, w...

 
HNQ
1:25 AM
3
Q: What does it mean when an isotope is stable?

inf3rnoDoes stable mean that an isotope has a very long half life, for example xenon-124 has a half life of 1.8 x 10^22 years, or does it mean that fissure is theoretically not possible, or does it mean that the isotope has a very long half life, but the exact number is unknown?

 
 
3 hours later…
HNQ
4:40 AM
1
Q: Lagrangian and Integration by Parts

UyttendaeleSay I have a Lagrangian density with kinetic term $\mathcal{L}_{kin} = \phi \Box \phi$. To derive the equations of motion, I could integrate by parts to obtain $\mathcal{L}_{kin}' = - (\partial_{\mu}\phi)(\partial_{\mu}\phi)$, then apply the Euler-Lagrange equations to obtain $2\Box\phi=0$. (Corr...

 
 
1 hour later…
HNQ
5:53 AM
1
Q: Contradictions of explanations for the speed of light

Sovereign InquiryI've recently started reading the book Biocentrism, by Robert Lanza and Bob Berman, which in its mind-blowing chapters, discusses the perceptions of reality, space, and time. Lanza states that: If one could travel at lightspeed, one would find oneself everywhere in the universe at once. This ind...

 
 
15 hours later…
HNQ
9:17 PM
1
Q: Tensor and Matrices

NoumenoSuppose that we are dealing with the following matrix: $$A=\begin{bmatrix}a_{00} & a_{01} \\ a_{10} & a_{11}\end{bmatrix}$$ but I don't want to use matrix notation, insted I want to use tensor notation, so I write this matrix as: $$A^{\mu}_{\nu}$$ Question is: $A^0_1$ is equal to $a_{01}$ or $a_{...

 

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