The Minimum Number of Multiplicity 1 Eigenvalues Among Real Symmetric Matrices Whose Graph is a Tree
Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
Let T be a tree, let S(T) denote the set of real symmetric matrices whose graph is T, and let U(T) be the minimum number of eigenvalues with multiplicity 1 among matrices in S(T). We show that if T ′ is a tree constructed by adding a pendent vertex to a diameter 5 tree T such that d(T) = d(T) ′ , then U(T ′ ) ≤ U(T). We then take this result as motivation to show results that are consistent with and suggest that if T ′ is a tree constructed by adding a pendent vertex to a tree T such that d(T) = d(T) ′ , then U(T ′ ) ≤ U(T). In particular, we show that the result is true for the case where T and T ′ are both linear trees, the case where T is a linear tree and T ′ is a nonlinear tree, and the case where T and T ′ are both minimally nonlinear trees such that U(T) = 2. We then construct a partial proof for the same and similar results where T and T ′ are general trees.
Zimmerman, Jacob, "The Minimum Number of Multiplicity 1 Eigenvalues Among Real Symmetric Matrices Whose Graph is a Tree" (2022). Undergraduate Honors Theses. William & Mary. Paper 1804.
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