Some inheritance properties for complementary basic matrices

We say that the product of a row vector and a column vector is intrinsic if there is at most one non-zero product of corresponding coordinates. Analogously we speak about intrinsic product of two or more matrices, as well as about intrinsic factorizations of matrices. Since all entries of the intrinsic product are products of entries of the multiplied matrices, there is no addition. The class of complementary basic matrices (CB-matrices) was recently introduced as matrices, if of order n  , A=Gi1Gi2⋯Gin-1A=Gi1Gi2⋯Gin-1, where (i1,i2,…,in-1)(i1,i2,…,in-1) is a permutation of (1,2,…,n-1),(1,2,…,n-1), and the matrices GkGk, k=1,…,n-1k=1,…,n-1 have the formGk=Ik-1CkIn-k-1for some 2×22×2 matrices CkCk. It was observed that (1) independently of the permutation, all such matrices with given CiCi’s have the same spectrum (though they do not form a similarity class), (2) the classical companion matrix belongs to the class of CB-matrices (M. Fiedler, A note on companion matrices, Linear Algebra Appl. 372 (2003) 325–331, [9]), (3) the multiplication of the GiGi’s is intrinsic. We explore connections between the 2×22×2 matrices CkCk and the resulting CB-matrix ΠGkΠGk; in particular, which properties are inherited from the CkCk to the ∏Gk∏Gk. We consider two situations, for the ordinary real CB-matrices and for the corresponding sign pattern matrices.