On primordial matter production induced by spatial curvature in the early universe

In this note, it is shown that nonvanishing spatial curvature produces primordial matter in the initially empty universe due to quantum gravity effects. This matter decays faster than radiation and is described by a stiff equation of state. The quantum Hamiltonian constraint equation for the universe with the maximally symmetric geometry is solved in the semi-classical approximation. The extra energy density and pressure of quantum origin that appear in the generalized Friedmann equations describe primordial matter and modify the expansion history of the early universe.