We prove an extension to R n , endowed with a suitable metric, of the relation between the Einstein-Hilbert action and the Dirac operator which holds on closed spin manifolds. By means of complex powers, we first define the regularised Wodzicki residue for a class of operators globally defined on R n . The result is then obtained by using the properties of heat kernels and generalised Laplacians.Keywords Wodzicki residue · Einstein-Hilbert action · Dirac operator Mathematics Subject Classification (2000) Primary 58J40; Secondary 58J42 · 47A10 · 47G30 · 47L15
IntroductionIn 1984 Wodzicki [38] introduced a trace on the algebra of classical pseudodifferential operators on a closed manifold M. A similar result was independently obtained by Guillemin [18], in order to give a soft proof of Weyl formula. The Wodzicki residue became then a standard tool in Non-commutative Geometry. In 1988, Connes [10] proved that, for operator of order − dim(M), Dixmier Trace and the Wodzicki residue are equivalent. Moreover, he conjectured that the Wodzicki residue could connect Dirac operators and Einstein-Hilbert actions on M. In 1995, Kastler [21], Kalau and Walze [19] proved this conjecture. Namely, let / D be the classical Atiyah-Singer