The global wave front set of tempered oscillatory integrals with inhomogeneous phase functions

Abstract: We study certain families of oscillatory integrals $I_\varphi(a)$, parametrised by phase functions $\varphi$ and amplitude functions $a$ globally defined on $\mathbb{R}^d$, which give rise to tempered distributions, avoiding the standard homogeneity requirement on the phase function. The singularities of $I_\varphi(a)$ are described both from the point of view of the lack of smoothness as well as with respect to the decay at infinity. In particular, the latter will depend on a version of the set of stationary points of $\varphi$, including elements lying at the boundary of the radial compactification of $\mathbb{R}^d$. As applications, we consider some properties of the two-point function of a free, massive, scalar relativistic field and of classes of global Fourier integral operators on $\mathbb{R}^d$, with the latter defined in terms of kernels of the form $I_\varphi(a)$.