Gravitation and Cosmology: Geometry, Dynamics, and the Ontology of Spacetime

This monograph develops a conceptually structured study of gravitation and cosmology, tracing the theory of General Relativity from its historical origins to its modern extensions in inflationary dynamics and gravitational particle production. Emphasis is placed not only on the mathematical formulation of the theory, but also on its conceptual foundations, including the Equivalence Principle, the Hole Argument, gauge covariance, and the physical interpretation of coordinates. The weak-field regime is analyzed from a dynamical perspective, followed by a detailed treatment of the Schwarzschild solution and gravitational collapse, with particular attention to the role of coordinate systems. Cosmological models are examined within both Newtonian and relativistic frameworks, and the nature of singularities is critically assessed. The later chapters develop quantum field theory in curved spacetime as a bridge between classical gravitation and quantum phenomena, focusing on gravitational particle production, reheating mechanisms, and quintessential inflation. Throughout, mathematical singularities and ultraviolet divergences are interpreted as indicators of theoretical limits rather than definitive physical realities. The work aims to integrate geometric, dynamical, and quantum aspects of gravitation within a unified conceptual framework, clarifying the relationship between mathematical structure and physical meaning.