“Hugh Everett's relative-state formulation of quantum mechanics is an attempt to solve the quantum measurement problem by dropping the collapse dynamics from the standard von Neumann-Dirac formulation of quantum mechanics.

For relativistic quantum mechanics the corresponding equation, which describes a free particle with zero spin, is called the Klein-Gordan equation and can be written in the formml: (1.1. 33) ∂ 2 Ψ ∂ t 2 = ∇ 2 Ψ − m 2 Ψ , where Ψ is the wavefunction and m is the normalized particle mass.

These are the wavefunction, matrix, path integral, phase space, density matrix, second quantization, variational, pilot wave, and Hamilton–Jacobi formulations.

The famous special-relativity equation that Einstein's theory introduced was that of e = m c 2 . In the formula, e stands for "energy," m stands for "mass," and c stands for "the speed of light." The consequences of the formula are many. First, one can conclude that energy and mass are proportional.