Let (X, h) be a compact and irreducible Hermitian complex space of complex dimension m. In this paper we are interested in the Dolbeault operator acting on the space of L 2 sections of the canonical bundle of reg(X), the regular part of X. More precisely let dm,0 : L 2 Ω m,0 (reg(X), h) → L 2 Ω m,1 (reg(X), h) be an arbitrarily fixed closed extension of ∂m,0 : L 2 Ω m,0 (reg(X), h) → L 2 Ω m,1 (reg(X), h) where the domain of the latter operator is Ω m,0 c (reg(X)). We establish various properties such as closed range of dm,0, compactness of the inclusion D(dm,0) → L 2 Ω m,0 (reg(X), h) where D(dm,0), the domain of dm,0, is endowed with the corresponding graph norm, and discreteness of the spectrum of the associated Hodge-Kodaira Laplacian d * m,0 • dm,0 with an estimate for the growth of its eigenvalues. Several corollaries such as trace class property for the heat operator associated to d * m,0 • dm,0, with an estimate for its trace, are derived. Finally in the last part we provide several applications to the Hodge-Kodaira Laplacian in the setting of both compact irreducible Hermitian complex spaces with isolated singularities and complex projective surfaces.
IntroductionConsider a complex projective variety V ⊂ CP n . The regular part of V , reg(V ), comes equipped with a natural Kähler metric g, which is the one induced by the Fubini-Study metric of CP n . In particular, whenever V has a nonempty singular set, we get an incomplete Kähler manifold of finite volume. In the seminal papers [10] and [22], given a singular projective variety V , many questions with a rich interaction of topology and analysis, for instance intersection cohomology, L 2 -cohomology and Hodge theory, have been raised for the incomplete Kähler manifold (reg(V ), g). Some of the most important among them are the Cheeger-Goresky-MacPherson's conjecture and the MacPherson's conjecture. The former, which is still open, says that the maximal L 2 -de Rham cohomology groups of (reg(V ), g) are isomorphic to the middle perversity intersection cohomology groups of V while the latter, proved in [29], asks whether the L 2 -∂-cohomology groups in bidegree (0, q) of (reg(V ), g) are 1 arXiv:1607.00289v3 [math.DG] 17 Feb 2018 * E,m,0 )}, has discrete spectrum.We point out explicitly that in the previous theorem the assumption concerning the parabolicity of (A h , g| A h ) does not depend on the particular Hermitian metric g that we fix on M . Indeed if g is another Hermitian metric on M then, since g and g are quasi-isometric on M , we have that (A h , g| A h ) is parabolic if and only if (A h , g | A h ) is parabolic. Consider again the setting of Theorem 0.1 and let ∂ t E,m,0 be the formal adjoint of ∂ E,m,0 with respect to g. Let ∆ ∂,E,m,0 : Ω m,0 (M, E) → Ω m,0 (M, E), ∆ ∂,E,m,0 = ∂ t E,m,0 • ∂ E,m,0 be the Hodge-Kodaira Laplacian in bidegree (m, 0). Since M is compact and ∆ ∂,E,m,0 is elliptic and formally self-adjoint we have that ∆ ∂,E,m,0 , acting on L 2 Ω m,0 (M, E, g) with domain Ω m,0 (M, E), is essentially self-adjoint. With * m,0 )}, has ...