Monday, November 13, 2023

Magnetic field of a rotating sphere calculated by rotating the frame

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In August 2023 we tried to calculate the gravity field of a spinning uniform ball, and got varying results. Maybe there were calculation err...
Sunday, November 12, 2023

Does nonlinearity of gravity make sense?

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On September 16, 2023 we wrote that nonlinearity of gravity leads to a strange result. Let us analyze this more. When does the nonlinearity ...
Thursday, November 9, 2023

Calculus of variations and a carpet

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(Photo Wikipedia) Let us present a simple example where charge conservation keeps the action such that it can be optimized strictly locally,...
Monday, November 6, 2023

A single accelerating particle breaks the Einstein field equations?

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UPDATE November 30, 2023: In the analysis of the Oppenheimer-Snyder collapse we assumed that Gauss's law for the gravity of a single par...
Sunday, November 5, 2023

A globally stationary point which is not locally stationary

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Suppose that we have a wall-to-wall carpet in a room, but the carpet is slightly too large and there is an annoying wrinkle in it.          ...
Saturday, November 4, 2023

Magically adding more charge to the Coulomb field

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Let us study the following problem. We have a magic device which can create an electric charge from nothing. We have a spherically symmetric...
Thursday, November 2, 2023

Einstein-Hilbert action: a flat metric is not a stationary point?

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UPDATE November 3, 2023: If we add an infinitesimal mass dM into empty Minkowski space, the change of the metric g is infinitesimal at any o...