Jottings

The Wigner rotation states that the successive action of two Lorentz boosts in arbitrary directions is equivalent to a single Lorentz boost followed by a spatial rotation. This article discusses the general case.

For the first-order small vibrations of a mechanical system near its stable equilibrium position, there exist normal modes equal in number to its degrees of freedom.

Small-amplitude vibrations of an incompressible elastic rope in a gravitational field.

If the pressures on both sides of a smooth adiabatic piston are equal but the temperatures are unequal, energy will transfer from the higher-temperature gas to the lower-temperature gas through microscopic vibrations of the piston, even when all heat conduction is neglected.

This article introduces the derivation process of the original form of Ampere’s Law and discusses its relationship with the modern form.