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HNQ
4:50 AM
4
Q: Is the event horizon of an extremal black-hole just a coordinate singularity?

AccidentalFourierTransformFor generic black holes one demonstrates that the event horizon is just a coordinate singularity by changing coordinates to a system where the metric is well defined. For example we have Kruskal-type coordinates $U_\pm\sim e^{\pm \kappa u_\pm}$ with $\kappa$ the surface gravity. In terms of these...

 
 
11 hours later…
HNQ
4:16 PM
2
Q: Why is there a density instead of mass in the Navier-Stokes Equation, if it's analogue to Newton's Second Law?

WybieI read in Ian Stewart's 17 Equations that Changed the World book that Navier-Stokes equation (I know it's not exactly a scientific book, but still, I'd like clarification on what is wrong if it's the case): $\rho \left( \dfrac{\partial v}{\partial t} + v \cdot \nabla v\right) = -\nabla p + \nabla...

 

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