We develop the theory of modulated operators in general principal ideals of compact operators. For Laplacian modulated operators we establish Connes' trace formula in its local Euclidean model and a global version thereof. It expresses Dixmier traces in terms of the vector-valued Wodzicki residue. We demonstrate the applicability of our main results in the context of log-classical pseudo-differential operators, studied by Lesch, and a class of operators naturally appearing in noncommutative geometry.where Res W (A) is the Wodzicki residue of A and Tr ω is any Dixmier trace.This theorem reduces the computation of Dixmier traces to that of the Wodzicki residue, which in turn is defined from the principal symbol of an operator and is therefore more accessible to computations. The spectral asymptotics of positive pseudo-differential operators was well known prior to Connes' trace formula by means of a Weyl law, see for instance [22, Chapter 29.1], but Connes' trace formula conceptualized Dixmier traces as an "integral" in noncommutative geometry. There were several attempts to extend and generalise Connes' trace formula (see e.g. [3], [15] and [19] for the treatment of anisotropic pseudo-differential operators, the perturbed Laplacian on the noncommutative two tori and manifolds with boundaries, respectively).
Recent developments.A recent extension of the above theorem appeared in [23] (see also [26]). It expresses the Dixmier traces of so-called Laplacian modulated operators (for rigorous definitions, see Section 4 below) in terms of a vector-valued Wodzicki residue, which again depends on the symbol of an operator. We state the main result of [23] here. Let ℓ ∞ (N) denote the Banach space of bounded sequences with supremum norm. Example 2.8. Let ϕ be a function satisfying (3) and (M, g) a closed Riemannian manifold. The Weyl law guarantees the eigenvalue asymptotics λ k ((1+∆ g ) d/2 ) = c g k+o(k) for a suitable constant c g > 0. Condition (3) implies that ϕ((1 − ∆ g ) d/2 ) ∈ L ϕ . Example 2.9. If (M, g) is a Riemannian manifold of dimension d, and ρ g denotes the geodesic distance, we can define an operator T : C ∞ c (M) → C ∞ (M) by (7) T f (x) := M f (x) − f (y) ρ g (x, y) d dV g ,