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Local realization of spectral clusters

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Abstract

Let λ\lambda be an isolated eigenvalue of multiplicity mm of a real Schrödinger operator on a compact connected manifold of dimension at least two, with a fixed closed, Dirichlet, or Neumann realization. Every symmetric matrix sufficiently close to λI\lambda I is the corresponding spectral-cluster matrix of a small scalar-potential perturbation supported in any prescribed nonempty interior open set. The perturbation depends 1/21/2-Hölder continuously on the matrix, vanishes at λI\lambda I, and is real analytic away from that value. Sections with these properties exist for positive Laplace eigenvalues in the full conformal class of a closed manifold and, in dimension at least three, for supported metric perturbations preserving the volume density pointwise.

For potentials and conformal factors, every nonzero scalar contraction of the intrinsic cokernel Hessian has infinite positive and negative index. The first nonzero transverse diagonal term of the contracted eigenfunction kernel is homogeneous and harmonic. On a closed manifold, the multiplicity locus in the full metric space or a full conformal class is a C1C^1 embedded submanifold exactly where the cluster derivative is onto. Unrestricted metric stability holds through multiplicity seven and can fail at multiplicity eight. For potentials and conformal metrics, the projection connection has arbitrary prescribed curvature at the reference along a compatible matrix germ. In particular, its local holonomy on the exact fixed-eigenvalue level is SO(m)\operatorname{SO}(m).

For a finite effective symmetry group, the matrix target is the self-adjoint commutant. In corank one, the same index condition gives continuous relative lifts over compact spaces of finite covering dimension. On each fixed harmonic space ⨁j=2Nℋj(S2)\bigoplus_{j=2}^N\mathcal H_j(S^2), the maximum width of the first N+1N+1 positive clusters is bounded below by a positive multiple of the squared L2L^2 norm of every sufficiently small conformal perturbation.

MSC 2020

58J50
Spectral problems; spectral geometry; scattering theory on manifolds
35P05
General topics in linear spectral theory for PDEs
35S05
Pseudodifferential operators as generalizations of partial differential operators
58C40
Spectral theory; eigenvalue problems on manifolds
53C29
Issues of holonomy in differential geometry
57R22
Topology of vector bundles and fiber bundles

Mathematics Subject Classification 2020

Record

Version DOI
10.5281/zenodo.23224622
All versions
10.5281/zenodo.22859621
Subjects
spectral cluster; Laplace operator; Schrödinger operator; local realization; multiplicity; holonomy; spectral rigidity
Language
English

Cite this paper

Anass Nifa. Local realization of spectral clusters. Preprint, Zenodo, v2 (2026). doi:10.5281/zenodo.23224622

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