Next we see why the causal wavelet B(Z), of the Kolmogoroff theory can be a divisor, namely, why the inverse does not diverge. We have our wavelet in the form B(Z)= eC(Z). Consider another wavelet A(Z) = e-C(Z), constructed analogously. By the same reasoning, at is also causal. Since A(Z)B(Z)=1, we have found a causal, inverse wavelet. This means that polynomial division with B(Z) should not give divergent coefficients. This property of the bt wavelet is often called minimum-phase, for reasons found in my book PVI. Other notable properties of a minimum-phase wavelet are: (1) Poles and zeros are outside the unit circle in the |Z|-plane; (2) Equivalent to transmitted waves in a layered medium where reflection coefficients are weaker than unity; (3) Phase at minus Nyquist equals that at plus Nyquist. (Observe this is not true for the pure delay operator .)