Fourier integral operators algebra and fundamental solutions to hyperbolic systems with polynomially bounded coefficients on R^n

We study the composition of an arbitrary number of Fourier integral operators $A_j$, $j=1,\dots,M$, $M\ge 2$, defined through symbols belonging to the so-called SG classes. We give conditions ensuring that the composition $A_1\circ\cdots\circ A_M$ of such operators still belongs to the same class. Through this, we are then able to show well-posedness in weighted Sobolev spaces for first order hyperbolic systems of partial differential equations with coefficients in SG classes, by constructing the associated fundamental solutions.Comment: 34 page

L^p(R^n)-continuity of translation invariant anisotropic pseudodifferential operators: a necessary condition

We consider certain anisotropic translation invariant pseudodifferential operators, belonging to a class denoted by $\mathrm{op}(\mathcal{M}^{\lambda}_{\psi})$, where $\lambda$ and $\psi=(\psi_1,\dots,\psi_n)$ are the "order" and "weight" functions, defined on $\mathbb{R}^n$, for the corresponding space of symbols. We prove that the boundedness of a suitable function $F_p\colon\mathbb{R}^n\to[0,+\infty)$, $1<p<\infty$, associated with $\lambda$ and $\psi$, is necessary to let every element of $\mathrm{op}(\mathcal{M}^{\lambda}_{\psi})$ be a $L^p(\mathbb{R}^n)$-multiplier. Additionally, we show that some results known in the literature can be recovered as special cases of our necessary condition.Comment: 16 pages, mistakes and typos correctio

Bounded Imaginary Powers of Differential Operators on Manifolds with Conical Singularities

We study the minimal and maximal closed extension of a differential operator A on a manifold B with conical singularities, when A acts as an unbounded operator on weighted L^p-spaces over B, 1 < p < \infty. Under suitable ellipticity assumptions we can define a family of complex powers A^z. We also obtain sufficient information on the resolvent of A to show the boundedness of the purely imaginary powers. Examples concern unique solvability and maximal regularity for the solution of the Cauchy problem for the Laplacian on conical manifolds as well as certain quasilinear diffusion equations.Comment: 27 pages, 3 figures (revised version 23/04/'02

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

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 $I_\varphi(a)$.Comment: 30 pages, 2 figures, mistakes and typos correctio

Magnetic Fourier Integral Operators

In some previous papers we have defined and studied a 'magnetic' pseudodifferential calculus as a gauge covariant generalization of the Weyl calculus when a magnetic field is present. In this paper we extend the standard Fourier Integral Operators Theory to the case with a magnetic field, proving composition theorems, continuity theorems in 'magnetic' Sobolev spaces and Egorov type theorems. The main application is the representation of the evolution group generated by a 1-st order 'magnetic' pseudodifferential operator (in particular the relativistic Schr\"{o}dinger operator with magnetic field) as such a 'magnetic' Fourier Integral Operator. As a consequence of this representation we obtain some estimations for the distribution kernel of this evolution group and a result on the propagation of singularities