Gaussian

Choosing initial_lapse = "gaussian" provides a gaussian bump in the initial lapse grid function alp. This is mainly useful for testing purposes.

$$\alpha = 1 + A \exp(-r^2/\sigma^2)$$

where the amplitude $A$ and square of the width $\sigma^2$ of the bump are set using the parameters gaussian_amplitude and gaussian_sigma2. This choice of lapse is commonly termed flatty.