Smoothing procedure is usually done in order to decrease the influence of noise and to reach analytical equality between all components of the signal. The ways of smoothing are numerous: interpolation, approximation, convolution, wavelets, etc.
My question is connected with convolution. It means that after convolving initial function with the special kernel we get the smoothed representation. Criterion of smoothing - the amount of extrema. The more it is, the less smoothed is the signal.
Lindberg proved that convolution with Gaussian function doesn't generate new extrema. My question is - are there any other functions, that also don't lead to appearance of new extrema? Or may be you'll introduce a well-known smoothing technique, familiar to you?
With respect,
Dmitrij