Perturbation-Response Protocols
Turn on perturbation at t = 0, and keep constant thereafter
- measured response is proportional to integral of time-integrated correlation function
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Apply as d-function pulse at t = 0, subsequent evolution proceeding normally
- measured response proportional to time correlation function itself
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Use a sinusoidally oscillating perturbation
- measured response proportional to Fourier-Laplace transformed correlation functions at the applied frequency
- extrapolate results from several frequencies to zero-frequency limit