FTP name the theory whose non-degenerate form states that the first order correction to the energy of an eigenstate is simply the expectation of P-hat, a namesake operator introduced to alter the Hamiltonian slightly.
In quantum mechanics, this may be used to obtain first order corrections for relativistic effects using h-bar-to-the-fourth p-hat-to-the-fourth over eight m-cubed c-squared as the namesake type of operator. This theory arises from consideration of an analytically unsolvable problem as the superposition of a spectral problem with known solution and a power series in an "order of approximation" parameter, which is generally symbolized lambda. Fermi's Golden Rules are statements of the asymptotic transition rates that the time-dependent variety of this gives in the sudden approximation. FTP name the theory whose non-degenerate form states that the first order correction to the energy of an eigenstate is simply the expectation of P-hat, a namesake operator introduced to alter the Hamiltonian slightly.
In quantum mechanics, this may be used to obtain first order corrections for relativistic effects using h-bar-to-the-fourth p-hat-to-the-fourth over eight m-cubed c-squared as the namesake type of operator.
(quantum mechanical) perturbation theory