As I know, the Fourier transform of the Gaussian function is also Gaussian.
The simple verification for that is shown below. http://mathworld.wolfram.com/FourierTransformGaussian.html
But fast Fourier transform(in Matlab) of the Gaussian function gives me some distribution, which oscillates its sign. However, its power spectrum looks like Gaussian. The results I got from Matlab are shown below.
Why does the sign of fast Fourier transform of the Gaussian function oscillate? I appreciate your attention and answers in advance.