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Derivations of the subalgebras intermediate the general linear Lie algebra and the diagonal subalgebra over commutative rings

Deng Yin Wang, Xian Wang (2008)

Archivum Mathematicum

Let R be an arbitrary commutative ring with identity, gl ( n , R ) the general linear Lie algebra over R , d ( n , R ) the diagonal subalgebra of gl ( n , R ) . In case 2 is a unit of R , all subalgebras of gl ( n , R ) containing d ( n , R ) are determined and their derivations are given. In case 2 is not a unit partial results are given.

Extremal functions of the Nevanlinna-Pick problem and Douglas algebras

V. Tolokonnikov (1993)

Studia Mathematica

The Nevanlinna-Pick problem at the zeros of a Blaschke product B having a solution of norm smaller than one is studied. All its extremal solutions are invertible in the Douglas algebra D generated by B. If B is a finite product of sparse Blaschke products (Newman Blaschke products, Frostman Blaschke products) then so are all the extremal solutions. For a Blaschke product B a formula is given for the number C(B) such that if the NP-problem has a solution of norm smaller than C(B) then all its extremal...

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