I am curious as to the differences, if one wishes to study the big bang and the origin of the universe, as his/hers primary studies. How would my field of study, and expertise differ coming from a theoretical physics background, compared to (theoretical) astrophysics? Would there be any practical differences in the workings as a theoretical astrophysicist, compared to being a theoretical physicist, interested in cosmology, such as Lawrence Krauss? I am I bound under more regulations as the astrophysicist, compared to a theoretical physicist? Which of the two disciplines is normally prefered, and would an astrophysics background still allow for speculations about Relativity and Quantum Mechanics role in these events, in my eventual papers? It's the same event unfolding, so how would the respectivr field differ?