# V. A. Strauss

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### Some class of real sequences having indefinite Hankel forms

Luis J. Navarro, Vladimir Strauss

MFAT **17** (2011), no. 1, 65-74

65-74

In this paper we generalize the results given in [14] about real sequences which are not necessarily positive (i.e, they are not sequences of power moments) but can be mapped, by a difference operator, into a power moment sequence. We prove by elementary methods that the integro-polynomial representation of such sequences remains after dropping the condition on its growth imposed in the mentioned article. Some additional results on the uniqueness of the representation are included.

### On models of function type for a special class of normal operators in Krein spaces and their polar representation

MFAT **13** (2007), no. 1, 67-82

67-82

The paper is devoted to a function model representation of a normal operator $N$ acting in a Krein space. We assume that $N$ and its adjoint operator $N^{\#}$ have a common invariant subspace $L_{+}$ which is a maximal nonnegative subspace and has a representation as a sum of a finite-dimensional neutral subspace and a uniformly positive subspace. For $N$ we construct a model representation as the multiplication operator by a scalar function acting in a suitable function space. This representation is applied to the problem of existence of a polar representation for normal operators of $D_{\kappa}^+$-class.

### On a spectral decomposition of a commutative operator family in spaces with indefinite metric

Tomas Ya. Azizov, Vladimir A. Strauss

MFAT **11** (2005), no. 1, 10-20

10-20

### A generalization of Gerisch's theorem on biorthogonal systems

MFAT **7** (2001), no. 4, 11-17

11-17