## HLATTICE

#### Zhiqi Huang (zhiqi.huang@cea.fr or zqhuang@cita.utoronto.ca)

- HLattice is a free code that simulates scalar fields and gravity in the early universe.
- The current version V2.0 is an easy-to-use version that uses an "all-in-one" configuration file. See the file "README.txt" in the package (a pdf manual coming soon).
- Integrator: you can choose between the 2nd, 4th and 6th symplectic integrators. The 6th symplectic integrator is accurate to $O(dt^6)$ (i.e., the error term is of order $dt^7$)
- Discretization: you can choose between "LatticeEasy scheme", "HLattice V1.0 scheme" and "HLattice V2.0 scheme". The "HLattice V2.0 scheme" calculates the Laplacian of fields ($\nabla^2 \phi$) to $O(dx^3)$ (i.e. the error term is of order $dx^4$).
- Metric: you can choose between "Minkowski background", "FRW background", "FRW with perturbations in synchronous gauge, fixed spatial coordinates" and "FRW with perturbations in synchronous gauge, adaptive spatial coordinates" (new feature in V2.0). The "adaptive spatial coordinates" is used to remove the gauge mode in synchronous gauge (corresponding to the freedom of choosing arbitrary spatial coordinates, i.e., gauge transformation $x^i => x^i + \zeta^i(x)$). For a problem that has a typical growing-mode wavenumber close to the Hubble parameter (k*~H) and that requires long time integration (# of efolds ~O(1)), the gauge mode is usually large. In such cases, if you want to include the metric feedback, you need to use the adaptive scheme.
- You can compile HLattice with the free compiler: gfortran + cpp preprocessor (comes with gcc).
- [Download HLattice V2.0]

comments:
- So far I haven't found a case where the metric feedback is important for preheating dynamics.
- The original paper is written for HLattice V1.0. An updated version for HLattice V2.0 is here.
- You may also want to try LatticeEasy by Gary Felder and Igor Tkachev, DEFROST by Andrei Frolov, CUDAEasy by Jani Sainio and PSpectRe by Richard Easther, Hal Finkel and Nathaniel Roth.

last updated:

Feb 27, 2012