2016AcA....66...75S

Light curves of superhumps and their evolution during superoutbursts are analyzed by decomposing them into their Fourier components, including the fundamental mode and the first three overtones. The amplitudes of the fundamental mode are found to decrease significantly during superoutburstwhile those of the overtones remain practically constant. The phases of maxima of the fundamental mode increase systematically during superoutburst while those of the overtones - systematically decrease. The combination ofthe two effects is responsible for the characteristic evolution of superhump light curves: the appearance and growth of the secondary humpsand the spurious phase jumps in the (O-C) diagrams. Two intrepretations are possible. Either that instead of just one superhumpperiod P_sh there are four periodsP_k which resemble - but are significantly different from - the fundamental mode and the first three overtones of P_sh. Or - morelikely - that those time-dependent phase shifts are genuine.