Electronic Journal of Differential Equations,
Vol. 2011 (2011), No. 89, pp. 1-11.

Title: Compact inverses of multipoint normal differential
       operators for first order
       
Authors: Zameddin I. Ismailov (Karadeniz Technical Univ., Trabzon, Turkey)
         Elif Otkun Cevik (Karadeniz Technical Univ., Trabzon, Turkey)
	 Erdal Unluyol    (Karadeniz Technical Univ., Trabzon, Turkey)

Abstract:
 In this work, we describe all normal extensions of a multipoint
 minimal operators generated by linear multipoint
 differential-operator expressions for first order in the
 Hilbert space of vector functions, in terms of boundary values
 at the endpoints of infinitely many separated subintervals.
 Also we investigate compactness properties of the inverses
 of such extensions. 

Submitted May 7, 2011. Published July 05, 2011.
Math Subject Classifications: 47A05, 47A20.
Key Words: Direct sum of Hilbert spaces and operators;  extension; 
           multipoint selfadjoint operator; formally normal operator;
           normal operator.