Title: Imaginary time, shredded propagator method for large-scale GW calculations,
Abstract: The GW method is a many-body approach capable of providing quasiparticle
bands for realistic systems spanning physics, chemistry, and materials science.
Despite its power, GW is not routinely applied to large complex materials due
to its computational expense. We perform an exact recasting of the GW
polarizability and the self-energy as Laplace integrals over imaginary time
propagators. We then "shred" the propagators (via energy windowing) and
approximate them in a controlled manner by using Gauss-Laguerre quadrature and
discrete variable methods to treat the imaginary time propagators in real
space. The resulting cubic scaling GW method has a sufficiently small prefactor
to outperform standard quartic scaling methods on small systems (>=10 atoms)
and also represents a substantial improvement over several other cubic methods
tested. This approach is useful for evaluating quantum mechanical response
function involving large sums containing energy (difference) denominators.