Quadratic forms and sesquilinear forms in infinite dimensional spaces. Witt type theorems in spaces of denumerably infinite dimension
For a block upper triangular matrix, a necessary and sufficient condition has been given to let it be the sum of block upper rectangular matrices satisfying certain rank constraints; see H. Bart, A. P. M. Wagelmans (2000). The proof involves elements from integer programming and employs Farkas' lemma. The algebra of block upper triangular matrices can be viewed as a matrix algebra determined by a pattern of zeros. The present note is concerned with the question whether the decomposition result referred...
An matrix with nonnegative entries is called row stochastic if the sum of entries on every row of is 1. Let be the set of all real matrices. For , we say that is row Hadamard majorized by (denoted by if there exists an row stochastic matrix such that , where is the Hadamard product (entrywise product) of matrices . In this paper, we consider the concept of row Hadamard majorization as a relation on and characterize the structure of all linear operators preserving (or...
Assume that K is an arbitrary field. Let (I,⪯) be a poset of finite prinjective type and let KI be the incidence K-algebra of I. A classification of all sincere posets of finite prinjective type with three maximal elements is given in Theorem 2.1. A complete list of such posets consisting of 90 diagrams is presented in Tables 2.2. Moreover, given any sincere poset I of finite prinjective type with three maximal elements, a complete set of pairwise non-isomorphic sincere indecomposable prinjective...
It is proved that generalized polynomials with rational exponents over a commutative field form an elementary divisor ring; an algorithm for computing the Smith normal form is derived and implemented.
In this paper, we determine all the normal forms of Hermitian matrices over finite group rings , where , is a commutative -group with order . Furthermore, using the normal forms of Hermitian matrices, we study the structure of unitary group over through investigating its BN-pair and order. As an application, we construct a Cartesian authentication code and compute its size parameters.