Green’s functions in the early universe

During the early era, the rapid expansion of the universe influences wave phenomena. To elicit the mode of propagation in this era, one can examine the Green function that is associated with the wave equation governing each phenomenon. This Green function will comprise a singular term, governing propagation with the characteristic speed, and a regular term which governs any propagation with lesser speeds. In the cosmological model of the early universe, the singular terms for both the electromagnetic and gravitational Green functions are deter­mined, and so is the regular term in the electromagnetic case. The regular term in the gravitational case is investigated, and its contribution to the gravitational potential is evaluated. The initial-value problem for gravi­tational waves in the model is solved in a closed form.