The Art of Lattice and Gravity Waves from Preheating
  The nonlinear dynamics of preheating after early-Universe inflation is often studied with lattice simulations. In this work I present a new lattice code HLATTICE. It differs from previous public available codes in the following three aspects: (i) A much higher accuracy is achieved with a modified sixth-order symplectic integrator; (ii) scalar, vector, and tensor metric perturbations in synchronous gauge and their feedback to the dynamics of scalar fields are all included; (iii) the code uses a projector that completely removes the scalar and vector components defined by the discrete spatial derivatives. Such a generic code can have wide range of applications. As an example, gravity waves from preheating after inflation are calculated with a better accuracy. 
Zhiqi Huang
astro-ph.CO gr-qc hep-ph hep-th