Pseudodifferential operators on prehomogeneous vector spaces
  Let $G_\C$ be a connected, linear algebraic group defined over $\R$, acting regularly on a finite dimensional vector space $V_\C$ over $\C$ with $\R$-structure $V_\R$. Assume that $V_\C$ posseses a Zariski-dense orbit, so that $(G_\C,\rho,V_\C)$ becomes a prehomogeneous vector space over $\R$. We consider the left regular representation $\pi$ of the group of $\R$-rational points $G_\R$ on the Banach space $\Cvan(V_\R)$ of continuous functions on $V_\R$ vanishing at infinity, and study the convolution operators $\pi(f)$, where $f$ is a rapidly decreasing function on the identity component of $G_\R$. Denote the complement of the dense orbit by $S_\C$, and put $S_\R=S_\C\cap V_\R$. It turns out that the restriction of $\pi(f)$ to $V_\R-S_\R$ is a smooth operator. Furthermore, if $G_\C$ is reductive, and $S_\C$ and $S_\R$ are irreducible hypersurfaces, $\pi(f)$ corresponds, on each connected component of $V_\R-S_\R$, to a totally characteristic pseudodifferential operator. We then investigate the restriction of the Schwartz kernel of $\pi(f)$ to the diagonal. It defines a distribution on $V_\R-S_\R$ given by some power $|p(m)|^s$ of a relative invariant $p(m)$ of $(G_\C,\rho,V_\C)$ and, as a consequence of the fundamental theorem of prehomogeneous vector spaces, its extension to $V_\R$, and the complex $s$-plane, satisfies functional equations. A trace of $\pi(f)$ can then be defined by subtracting the singular contributions of the poles of the meromorphic extension. 
Pablo Ramacher (Berlin)