  Field amplification and particle production due to parametric resonance are
highly nontrivial predictions of quantum fields that couple to an oscillating
source during inflation and reheating. Understanding this two effects is
crucial for the connection between the resonance phenomenon and precise
observational data. In this paper, we give a general and analytic analysis of
parametric resonance of relevant field modes evolving during inflation and
reheating by using the uniform asymptotic approximation. This analysis can
provide a clear and quantitative explanation for the field amplification and
particle production during the resonance. The potential applications of our
results to several examples, including sound resonance during inflation,
particle productions during reheating, and parametric resonance due to
self-resonance potentials, have also been explored. The formalism developed in
this paper is also applicable to parametric resonance in a broad areas of
modern science.
