On Shell And Off Shell
In physics, particularly in quantum field theory, configurations of a physical system that satisfy classical equations of motion are called on shell, and those that do not are called off shell.
For instance, in classical mechanics in the action formulation, extremal solutions to the variational principle are on shell and the Euler-Lagrange equations are on shell equations (i.e., they do not hold off shell). Noether's theorem is also another on shell theorem.
Read more about On Shell And Off Shell: Mass Shell
Famous quotes containing the word shell:
“I was even more surprised at the power of the waves, exhibited on this shattered fragment, than I had been at the sight of the smaller fragments before. The largest timbers and iron braces were broken superfluously, and I saw that no material could withstand the power of the waves; that iron must go to pieces in such a case, and an iron vessel would be cracked up like an egg- shell on the rocks.”
—Henry David Thoreau (1817–1862)