A relativistic particle is a particle moving with a speed close to the speed of light, such that effects of special relativity are important for the description of its behavior.
Massless particles (e.g., photons) are always moving at the speed of light, therefore they are always relativistic.
Massive particles are relativistic when their kinetic energy is comparable or greater than the energy corresponding to their rest mass. (This condition implies that their speed is close to the speed of light.) Such relativistic particles are generated in particle accelerators, and are naturally occurring in cosmic radiation. In astrophysics, jets of relativistic plasma are produced by the centers of active galaxies and quasars.
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An Introduction to the Lorentz-Dirac Equation - Notes by Eric Poisson providing two derivations of the Lorentz--Dirac equation.
Relativistic quantum mechanics - An electronic textbook for relativistic quantum mechanics is presented. It can be ordered free
Meta Description: [ A textbook for relativistic quantum mechanics is
presented. The Dirac equation, its nonrelativistic limits, parity, the total angular
momentum etc. are derived. This publication can be ordered for free. ]
Selected Papers on Geometric Algebra in Quantum Mechanics - These papers analyze the quantum mechanical Dirac theory of the electron with respect to its geometric structure as revealed by reformulation in terms of Spacetime Algebra
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The Klein-Gordon Field - A brief overview of the lagrangian for a Klein-Gordon field, by Professor John Norbury.
The Quantum Theory of Particles - A new approach to relativity, quantum mechanics, and field theory which solves many old puzzles, such as ultraviolet infinities and superluminal spreading of wave packets.
Meta Description: [ Quantum mechanics and special relativity can be combined without divergences and contradictions. To do that we need to reformulate the Hamiltonian of the Quantum Field Theory and to admit that Lorentz transformations for time and position are not universal and exact: they depend on interactions. ]
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