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2:00 AM
6
Q: John, in his spaceship traveling at relativistic speed, is crossing the Milky Way in 500 years. How many supernovae explosions would he experience?

Alexandre BartHe is moving at a stable speed, and crossing the Milky Way in 500 years of his own time. From my reference frame on earth, his trip would take 100,000 years, and so, he should experience thousands of supernovae explosions, shouldn’t he? But from his frame of reference, he’s seeing the Milky Way m...

4
Q: Uniqueness of Maxwell Lagrangian

zeroknowledgeproverIn the textbook Condensed Matter Field Theory by Atland and Simons, it is said that the Maxwell Lagrangian $\mathcal{L}$ coupled to a four-current $j^\mu$ satisfying $\partial_\mu j^\mu = 0$ is the unique Lagrangian that is gauge invariant and Lorentz invariant up to quadratic order in $A_\mu$, i...

 
1 hour later…
HNQ
HNQ
3:21 AM
1
Q: Why, when we calculate forces in banking of roads, we do not take the centripetal force but the centrifugal force?

Gaurav BatraI know the we only apply centrifugal force when in non inertial frame of the object but in banking of road questions, why cant we make equations from inertial frame rather than non inertial frame? Above are the equations for a car in the frame of the car on questions of a banked road. Here we ta...

 
2 hours later…
HNQ
HNQ
5:22 AM
1
Q: What does "DC" mean in gravitational physics?

Níckolas AlvesI have came across a few works in gravitational physics using the term "DC" without further explanation of its meaning. For example, consider Strominger's 1703.05448, which states in p. 2 about the memory effect that This is a subtle DC effect, in which the passage of gravitational waves produce...


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