Gravitational Waves from Astrophysical and Cosmological Sources

In this talk I will briefly review how to implement computation of gravitational waves (GWs) from some astrophysical and cosmological sources. As for the former, GWs from binaries of compact objects, such as black holes and neutron stars, can be computed typically by the following methods: (i) Post Newtonian approximations for comparable mass binaries, (ii) point-particle and semi-relativistic approximations for extreme-mass-ratio binaries. As for the latter, colliding bubbles in the early Universe can be possible sources for GWs, which can be computed via (iii) the dynamics of a scalar field coupled to gravity, based on the collision mechanism modeled by the Coleman-de Luccia instanton. In addition to these, I will also discuss the possible production of GWs from the evolution of a thin-shell bubble in the context of the information loss problem.