We consider the index problem of certain boundary groupoids of the form $\mathcal{ G} = M _0 \times M _0 \cup \mathbb{ R}^q \times M _1 \times M _1$. Since it has been shown that for the case that $q \geq 3$ is odd, $K _0 (C^* (\mathcal{ G})) \cong \bbZ $, and moreover the $K$-theoretic index coincides with the Fredholm index, we attempt in this paper to derive a numerical formula for elliptic differential operators on $\mathcal{ G}$. Our approach is similar to that of renormalized trace of Moroianu and Nistor \cite{ Nistor;Hom2}. However, we find that when $q \geq 3$, the eta term vanishes, and hence the $K$-theoretic and Fredholm indices of elliptic (respectively fully elliptic) pseudo-differential operators on these groupoids are given only by the Atiyah-Singer term. As for the $q=1$ case we find that the result depends on how the singularity set $M_1$ lies in $M$.

Categories: math.OA math.DG math.KT

Renormalized Index Formulas for Elliptic Differential Operators on Boundary Groupoids