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Pairs of Clifford algebras of the Hurwitz type

Wiesław Królikowski (1996)

Banach Center Publications

For a given Hurwitz pair [ S ( Q S ) , V ( Q V ) , o ] the existence of a bilinear mapping : C ( Q S ) × C ( Q V ) C ( Q V ) (where C ( Q S ) and C ( Q V ) denote the Clifford algebras of the quadratic forms Q S and Q V , respectively) generated by the Hurwitz multiplication “o” is proved and the counterpart of the Hurwitz condition on the Clifford algebra level is found. Moreover, a necessary and sufficient condition for "⭑" to be generated by the Hurwitz multiplication is shown.

Pairs of k -step reachability and m -step observability matrices

Augusto Ferrante, Harald K. Wimmer (2013)

Special Matrices

Let V and W be matrices of size n × pk and qm × n, respectively. A necessary and sufficient condition is given for the existence of a triple (A,B,C) such that V a k-step reachability matrix of (A,B) andW an m-step observability matrix of (A,C).

Partial choice functions for families of finite sets

Eric J. Hall, Saharon Shelah (2013)

Fundamenta Mathematicae

Let m ≥ 2 be an integer. We show that ZF + “Every countable set of m-element sets has an infinite partial choice function” is not strong enough to prove that every countable set of m-element sets has a choice function, answering an open question from . (Actually a slightly stronger result is obtained.) The independence result in the case where m = p is prime is obtained by way of a permutation (Fraenkel-Mostowski) model of ZFA, in which the set of atoms (urelements) has the structure of a vector...

Partial sum of eigenvalues of random graphs

Israel Rocha (2020)

Applications of Mathematics

Let G be a graph on n vertices and let λ 1 λ 2 ... λ n be the eigenvalues of its adjacency matrix. For random graphs we investigate the sum of eigenvalues s k = i = 1 k λ i , for 1 k n , and show that a typical graph has s k ( e ( G ) + k 2 ) / ( 0 . 99 n ) 1 / 2 , where e ( G ) is the number of edges of G . We also show bounds for the sum of eigenvalues within a given range in terms of the number of edges. The approach for the proofs was first used in Rocha (2020) to bound the partial sum of eigenvalues of the Laplacian matrix.

Patterns with several multiple eigenvalues

J. Dorsey, C.R. Johnson, Z. Wei (2014)

Special Matrices

Identified are certain special periodic diagonal matrices that have a predictable number of paired eigenvalues. Since certain symmetric Toeplitz matrices are special cases, those that have several multiple 5 eigenvalues are also investigated further. This work generalizes earlier work on response matrices from circularly symmetric models.

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