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Published online by Cambridge University Press: 09 August 2007
In this paper we study linear fractional relations defined in the following way. Let
i,
'i, i = 1,2, be Banach spaces. We denote the space of bounded linear operators by
. Let T ε
(
1 ⊕
2,
'1 ⊕
'2). To each such operator there corresponds a 2 × 2 operator matrix of the form(*)
where T ij ε
(
j ,
'i . For each such T we define a set-valued map G T from
(
1,
2) into the set of closed affine subspaces of
(
'1,
'2) by
The map G T is called a linear fractional relation.
The paper is devoted to the following two problems.
• Characterization of operator matrices of the form (*) for which the set G T(K) is non-empty for each K in some open ball of the space
(
1,
2).
• Characterizations of quadruples (
1,
2,
'1,
'2) of Banach spaces such that linear fractional relations defined for such spaces satisfy the natural analogue of the Liouville theorem “a bounded entire function is constant”.