clear all;
% Grid:
L = 20;
N = 2^8;
x2 = linspace(-L/2,L/2,N+1);
x = x2(1:N);
k = 2*pi/L*[0:(N/2-1) (-N/2):-1];
%
omega = 1;
f = exp(-x.^2);
ft = fft(f);
%
yt = ft./(k.^2+omega);
y = ifft(yt);
plot(x,y);