Gram mates, sign changes in singular values, and isomorphism

2023/04/16 by Sooyeong Kim, Kim, Sooyeong, Steve Kirkland +1 · 2 citations
Computer Science · Engineering · Mathematics · #15A18 (Primary) #91D30 (Secondary) #Combinatorics (math.CO) #FOS: Mathematics #Mathematics and Applications #Matrix Theory and Algorithms #Spectral Theory (math.SP) #graph theory and CDMA systems

paper · pdf · doi:10.48550/arxiv.2304.07868

openalex publication_date 2023/04/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We study distinct (0,1) matrices A and B, called Gram mates, such that AA^T=BB^T and A^TA=B^TB. We characterize Gram mates where one can be obtained from the other by changing signs of some positive singular values. We classify Gram mates such that the rank of their difference is at most 2. Among such Gram mates, we further produce equivalent conditions in order that one is obtained from the other by changing signs of at most 2 positive singular values. Moreover, we provide some tools for constructing Gram mates where the rank of their difference is more than 2. Finally, we characterize non-isomorphic Gram mates whose difference is of rank 1 with some extra conditions.

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