A Fortran Code for Null Geodesic Solutions in the Lemaitre-Tolman-Bondi Spacetime

TL;DR

This paper presents a Fortran 77 code, SIMU, for simulating null geodesics in LTB spacetime, enabling detailed observational relation analysis with adaptable features and graphical output capabilities.

Contribution

Introduces a modular Fortran 77 code for numerical null geodesic solutions in LTB spacetime, facilitating observational studies and adaptable to various applications.

Findings

Code produces scale-invariant solutions of average density.

Graphical output integrated with GNUPLOT.

Code is easily adaptable for different LTB applications.

Abstract

This paper describes the Fortran 77 code SIMU, version 1.1, designed for numerical simulations of observational relations along the past null geodesic in the Lemaitre-Tolman-Bondi (LTB) spacetime. SIMU aims at finding scale invariant solutions of the average density, but due to its full modularity it can be easily adapted to any application which requires LTB's null geodesic solutions. In version 1.1 the numerical output can be read by the GNUPLOT plotting package to produce a fully graphical output, although other plotting routines can be easily adapted. Details of the code's subroutines are discussed, and an example of its output is shown.