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168,695 papers · 148 categories

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4794140187 · May 202619922001200920172026
48 results for Fredholm operator

The paper calculates indices for families of Fredholm operators and their extensions.

problem Calculating indices for families of Fredholm operators and their extensions.
method Passing from a Fredholm operator to its graph, deforming the horizontal subspace.
result Index formulas for families of Fredholm realizations and self-adjoint extensions.

New Fredholm criteria for pseudodifferential operators on manifolds.

problem Characterizing the Fredholm property of GG-pseudodifferential operators.
method General Simonenko principle applied to GG-pseudodifferential operators on Sobolev spaces of sections of vector bundles.
result Derivation of novel Fredholm criteria and further characterization for finite groups.

The spectral flow theorem is applied to operators on finite intervals.

problem Operators on finite intervals without boundary conditions are not Fredholm.
method Interpolation theory is used to define boundary conditions making the operators Fredholm. The spectral flow theorem is applied to find the Fredholm index.
result The Fredholm index is given by the spectral flow of the operator path.

Study perturbs APS boundary conditions for Lorentzian Dirac operators.

problem Maintaining Fredholmness of Dirac operators under perturbations of APS boundary conditions.
method Develop criteria for perturbing compact pairs of projections to remain Fredholm.
result Criteria for perturbing APS boundary conditions without losing Fredholmness.

Study shows Fredholmness of a Lorentzian Dirac operator on spacetimes.

problem Analyzing Fredholmness of a Lorentzian Dirac operator on spacetimes.
method Investigates Fredholmness of a (spatial) Γ-invariant Lorentzian Dirac operator under (anti) Atiyah-Patodi-Singer boundary conditions.
result Demonstrates Fredholmness of the operator in the von Neumann sense.

Derives Fredholm criteria for isotypical components from a Simonenko principle.

problem Finding Fredholm conditions for isotypical components of invariant pseudodifferential operators.
method General Simonenko's local principle and equivariant local principle for restriction to isotypical components.
result Full proof of equivariant local principle and extension of results.

We prove some Fredholm conditions for many algebras of differential operators on particular classes of open manifolds, which include asymptotically Euclidean or asymptotically hyperbolic manifolds. Our typical result is that an operator PP is Fredholm if, and only if, it is elliptic and some limit operators $(P_α)_{α\…

2018-08-04abs ↗pdf ↗

We construct a Fredholm module on self-similar sets such as the Cantor dust, the Sierpinski carpet and the Menger sponge. Our construction is a higher dimensional analogue of Connes' combinatorial construction of the Fredholm module on the Cantor set. We also calculate the Dixmier trace of two operators induced by the …

2019-12-12abs ↗pdf ↗

We describe two topologies on the space of unbounded Fredholm operators and we explain their K-theoretic relevance. In the process we also prove a very general result concerning the continuity of families of first order, elliptic boundary value problems.

2000-05-09abs ↗pdf ↗

Fredholm conditions for invariant operators on compact manifolds.

problem Characterizing operators with Fredholm maps induced by their action on manifolds.
method Defining transversally αα-elliptic operators and proving Fredholmness based on their principal symbols and group actions.
result Operators are Fredholm if and only if they are transversally αα-elliptic.

Researchers prove Fredholm property for Dirac operator on specific spacetimes.

problem Proving Fredholm property for Dirac operator on asymptotically static spacetimes.
method Combining time-dependent scattering theory and Egorov's theorem for pseudo-differential hyperbolic systems.
result The Dirac operator is Fredholm under Atiyah-Patodi-Singer boundary conditions.

The paper studies elliptic operators on manifolds with boundary.

problem Characterizing boundary conditions for elliptic operators on manifolds.
method Using Calderón projectors and mixed order Sobolev spaces, the paper describes the space of boundary values and characterizes Fredholm and regular realisations.
result Characterization of boundary conditions for elliptic operators leading to Fredholm and regular realisations.

Characterizes Fredholm conditions for group-invariant pseudodifferential operators.

problem Understanding Fredholm conditions for operators on quotient spaces.
method Study of symbol CC^*-algebra and topology of primitive ideal spectrum.
result Explicit characterization of Fredholm operators in terms of principal symbol and group action.

Extends Atiyah-Singer Dirac operator study to non-compact spacetimes.

problem Analyzing Dirac operator on non-compact spacetimes with non-compact Cauchy hypersurface.
method Building on previous works, extends Fredholm result to non-compact Lorentzian spaces, using von Neumann algebras and Galois coverings.
result Γ-Fredholmness of the Dirac operator under APS boundary conditions.

This article provides a version of scale calculus geared towards a notion of (nonlinear) Fredholm maps between certain types of Frechet spaces, retaining as many as possible of the properties Fredholm maps between Banach spaces enjoy, and the existence of a constant rank theorem for such maps. It does so by extending t…

2016-02-23abs ↗pdf ↗

We show that the existence of a Fredholm element of the zero calculus of pseudodifferential operators on a compact manifold with boundary with a given elliptic symbol is determined, up to stability, by the vanishing of the Atiyah-Bott obstruction. It follows that, up to small deformations and stability, the same symbol…

2006-07-06abs ↗pdf ↗

Develops calculus for QFB metrics, proving Fredholm properties and decay of harmonic forms.

problem Analyzing differential operators on quasi-fibered boundary metrics.
method Introduces pseudodifferential calculus, principal symbols, and Fredholm theory.
result Hodge-deRham operator is Fredholm on QFB Sobolev spaces and L2L^2 harmonic forms decay.

We show that elliptic complexes of (pseudo)differential operators on smooth compact manifolds with boundary can always be complemented to a Fredholm problem by boundary conditions involving global pseudodifferential projections on the boundary (similarly as the spectral boundary conditions of Atiyah, Patodi and Singer …

2015-10-08abs ↗pdf ↗

We review the concepts of the index of a Fredholm operator, the spectral flow of a curve of self-adjoint Fredholm operators, the Maslov index of a curve of Lagrangian subspaces in symplectic Hilbert space, and the eta invariant of operators of Dirac type on closed manifolds and manifolds with boundary. We emphasize var…

2003-04-15abs ↗pdf ↗

Novel approach to Nash equilibrium in mean-field stochastic games with operator resolvents.

problem Finding Nash equilibrium in mean-field stochastic games with mean-field interaction.
method Proposed a novel approach to derive Nash equilibrium semi-explicitly using operator resolvents and stochastic Fredholm equations.
result Equilibrium of the NN-player game converges to mean-field equilibrium, and ε\varepsilon-Nash equilibrium derived as a by-product.

Derives numerical formulas for elliptic differential operators on specific groupoids.

problem Index problem of elliptic differential operators on boundary groupoids.
method Similar to Moroianu and Nistor's renormalized trace approach, focusing on eta and Atiyah-Singer terms.
result For q3q \geq 3, KK-theoretic and Fredholm indices are given by the Atiyah-Singer term.

We explain the topology of the space, so called, Fredholm-Lagrangian-Grassmannain and the quantity ``Maslov index'' for paths in this space based on the standard theory of Functional Analysis. Our standing point is to define the Maslov index for arbitrary paths in terms of the fundamental spectral property of the Fredh…

2003-11-27abs ↗pdf ↗

Let X be a smooth compact manifold with boundary. For smooth foliations on the boundary of X admitting a `resolution' in terms of a fibration, we construct a pseudodifferential calculus generalizing the fibred cusp calculus of Mazzeo and Melrose. In particular, we introduce certain symbols leading to a simple descripti…

2010-09-22abs ↗pdf ↗

Develops tools for studying intersections of elliptic operators, focusing on JJ-holomorphic maps.

problem Intersection questions for families of elliptic operators.
method Equivariant Brill-Noether theory applied to Fredholm operators.
result Wendl's super-rigidity conjecture is proven.

Formula calculates index for CR operators on surfaces with boundary punctures.

problem Computing the index for Cauchy-Riemann operators on surfaces with boundary punctures.
method Large antilinear deformations method, generalized to punctured surfaces.
result Involves a non-standard weighted count of boundary zeros in the Euler characteristic term.

Study of elliptic boundary value problems on non-compact manifolds.

problem Analyzing elliptic differential operators on manifolds with non-compact boundaries.
method Regularity theory and trace theorems for sections in the maximal domain under various assumptions.
result Systematic study of local and nonlocal boundary conditions, including the Atiyah-Patodi-Singer condition.

The aim of this paper is to present the construction, out of the Kohn-Rossi complex, of a new hypoelliptic operator QLQ_{L} on almost CR manifolds equipped with a real structure. The operator acts on all (p,q)-forms, but when restricted to (p,0)-forms and (p,n)-forms it is a sum of squares up to sign factor and lower o…

2008-08-27abs ↗pdf ↗

This paper provides a KK-theoretic obstruction for higher kernel dimension for Dirac operators. For this we use a fibre-wise Dirac operator that gives rise to a family of Fredholm operators representing a class in topological KK-theory. Then Chern classes of this KK-class contain some information about the kernel of…

2018-02-19abs ↗pdf ↗

The Fredholm integral equation of the first kind improves solutions for ill-posed supervised learning problems with limited data.

problem Ill-posed supervised learning problems with insufficient data.
method Using the Fredholm integral equation of the first kind (FIFK) with semi-supervised assumptions and MSDF methods.
result Improved accuracy and stability in solutions for ill-posed problems.

Let $\Y$ be a smooth connected manifold, $Σ\subset\C$ an open set and $(σ,y)\to\scrP_y(σ)$ a family of unbounded Fredholm operators DH1H2D\subset H_1\to H_2 of index 0 depending smoothly on $(y,σ)\in \Y\times Σ$ and holomorphically on σσ. We show how to associate to $\scrP$, under mild hypotheses, a smooth vector bundle …

2013-01-24abs ↗pdf ↗

Injective and surjective neural operators for function spaces.

problem Tackles injective and surjective neural operators in function spaces.
method Combines prior work in ReLU and operator learning, uses Fredholm theory and Leray-Schauder degree theory.
result Injective and surjective neural operators are universal approximators and maintain their properties in finite-rank implementations.