PSpectCosmo: A Pseudo-Spectral Code for Cosmological Dynamics Spanning Inflation and Reheating

Abstract: \texttt{PSpectCosmo} is a high-performance \texttt{C++} program developed to investigate early-universe cosmological dynamics, with a specific emphasis on the inflationary epoch. Utilizing a Fourier-space pseudo-spectral method, \texttt{PSpectCosmo} enables the precise evolution of interacting scalar fields and gravitational waves, ensuring accurate representation of the power spectrum during inflation. This approach overcomes key limitations of finite difference methods, particularly in maintaining consistency between effective and lattice wave vectors. The code employs the adaptive step size velocity-Verlet algorithm for time integration, offering a balance of numerical stability and high precision. Additionally, \texttt{PSpectCosmo} incorporates a robust mechanism to compute convergent energy density, effectively resolving the issue of divergent energy density at the onset of inflation. These capabilities establish \texttt{PSpectCosmo} as a reliable and versatile tool for probing non-linear cosmological phenomena and inflationary dynamics with exceptional accuracy. The code is publicly available at https://github.com/JieJiang-Cosmology/PSpectCosmo.git