Weighted Singular Differential Operators in the Limit-Circle Case

1972 ◽  
Vol s2-4 (4) ◽  
pp. 741-744 ◽  
Author(s):  
Philip W. Walker
Keyword(s):  
Differential Operators ◽  
Limit Circle ◽  
Limit Circle Case ◽  
Circle Case

scholarly journals Second-Order Differential Operators in the Limit Circle Case

2021 ◽  
Author(s):  
Dmitri R. Yafaev ◽  
◽  
◽  
Keyword(s):  
Differential Equation ◽  
Differential Operators ◽  
Second Order ◽  
Spectral Measures ◽  
Limit Circle ◽  
Jacobi Operators ◽  
Limit Circle Case ◽  
Circle Case ◽  
Stieltjes Transforms

We consider symmetric second-order differential operators with real coefficients such that the corresponding differential equation is in the limit circle case at infinity. Our goal is to construct the theory of self-adjoint realizations of such operators by an analogy with the case of Jacobi operators. We introduce a new object, the quasiresolvent of the maximal operator, and use it to obtain a very explicit formula for the resolvents of all self-adjoint realizations. In particular, this yields a simple representation for the Cauchy-Stieltjes transforms of the spectral measures playing the role of the classical Nevanlinna formula in the theory of Jacobi operators.

scholarly journals ON THE ESSENTIAL SPECTRA OF GENERAL DIFFERENTIAL OPERATORS

1999 ◽  
Vol 30 (2) ◽  
pp. 105-126
Author(s):  
SOBHY EL-SAYED IBRAHIM
Keyword(s):  
Discrete Spectrum ◽  
Differential Operators ◽  
Integral Operators ◽  
Essential Spectra ◽  
Limit Circle ◽  
All Solutions ◽  
Limit Circle Case ◽  
Complex Coefficients ◽  
Well Posed ◽  
Circle Case

In this paper, it is shown in the cases of one and two singular end-points and when all solutions of the equation $M[u]-\lambda uw=0$, and its adjoint $M^+[v] -\lambda wv = 0$ are in $L_w^2 (a, b)$ (the limit circle case) with $f\in L^2_w(a,b)$ for $M[u]-\lambda wu=wf$ that all well-posed extensions of the minimal operator $T_0(M)$ generated by a general ordinary quasi-differential expression $M$ of $n$-th order with complex coefficients have resolvents which are Hilbert-Schmidt integral operators and consequently have a wholly discrete spectrum. This implies that all the regularly slovable operators have all the standard essential spectra to be empty. These results extend those of formally symmetric expression $M$ studied in [1] and [12], and also extend those proved in [8] in the case of one singular end-point of the interval [a,b).

The limit-circle case for a positive definite $J$ -fraction

1945 ◽  
Vol 12 (2) ◽  
pp. 255-273 ◽  
Author(s):  
Joseph J. Dennis ◽  
H. S. Wall
Keyword(s):  
Positive Definite ◽  
Limit Circle ◽  
Limit Circle Case ◽  
Circle Case

The spectra of well-posed operators

1995 ◽  
Vol 125 (6) ◽  
pp. 1331-1348 ◽  
Author(s):  
Sobhy El-sayed Ibrahim
Keyword(s):  
Adjoint Equation ◽  
Integral Operators ◽  
Essential Spectra ◽  
Limit Circle ◽  
All Solutions ◽  
Limit Circle Case ◽  
Complex Coefficients ◽  
Well Posed ◽  
Circle Case ◽  
Quasidifferential Expression

In this paper, the general ordinary quasidifferential expression M of nth order, with complex coefficients, and its formal adjoint M− are considered. It is shown in the case of two singular endpomts and when all solutions of the equation and the adjoint equation are in (the limit-circle case) that all well-posed extensions of the minimal operator T0(M) have resolvents which are Hilbert Schmidt integral operators and consequently have a wholly discrete spectrum. This implies that all the regularly solvable operators have all of the standard essential spectra to be empty. These results extend those for the formally symmetric expression M studied in [1] and [14], and also extend those proved in [8] for one singular endpoint.

scholarly journals An Alternate Proof of the De Branges Theorem on Canonical Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Keshav Raj Acharya
Keyword(s):  
Canonical System ◽  
Alternative Proof ◽  
Defect Index ◽  
Alternate Proof ◽  
Symmetric Relation ◽  
Canonical Systems ◽  
Limit Circle ◽  
Limit Circle Case ◽  
Limit Point Case ◽  
Circle Case

The aim of this paper is to show that, in the limit circle case, the defect index of a symmetric relation induced by canonical systems, is constant on ℂ. This provides an alternative proof of the De Branges theorem that the canonical systems with tr H1 imply the limit point case. To this end, we discuss the spectral theory of a linear relation induced by a canonical system.

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