The phase change caused by an amplifier directly depends on its gain and vice-versa owing to these relations. For 10 points each:
[10h] Name these doubly eponymous relations which apply to linear response functions. These statements relate the imaginary and real parts of a function that is analytic in the upper half plane.
ANSWER: Kramers-Kronig Relations [prompt on phase-gain relations]
[10m] Frequency response functions are the Fourier transforms of this type of function, which describe how a system responds to a point disturbance.
ANSWER: Green’s functions [accept transfer functions ; prompt on correlation function or two-point function]
[10e] The Kramers-Kronig relations apply to causal Green’s functions, which have no effect for times before the impulse. As such, those functions have this property for ‘t less than t prime’; the derivative of a constant function also has this property.
ANSWER: being equal to zero [accept obvious equivalents]