The Fourier regularization approach is formally described starting with Equation (1.6), and replacing Q and its inverse with the unitary matrix F that performs Fourier transformation, and its inverse Working in the Fourier index domain enables simple manipulations to directly suppress oscillations and unphysical features, and to introduce desired features, before converting back to the relaxation rate domain. Conventional regularization methods also suppress oscillations and create smoothness in the spectral domain. This is achieved, for example, by imposing non-negativity. Also, instead of truncating the singular values and vectors, Tikhonov regularization imposes smoothness and suppresses baseline distortions using a regularization constant  and by replacing reciprocals of singular values in Equation (2.11) by