
arXiv: 2206.03983
A recent result of Cioabă, Dewar and Gu implies that any $k$-regular Ramanujan graph with $k \geq 8$ is globally rigid in $\mathbb{R}^2$. In this paper, we extend these results and prove that any $k$-regular Ramanujan graph of sufficiently large order is globally rigid in $\mathbb{R}^2$ when $k\in \{6, 7\}$, and when $k\in \{4,5\}$ if it is also vertex-transitive. These results imply that the Ramanujan graphs constructed by Morgenstern in 1994 are globally rigid. We also prove several results on other types of framework rigidity, including body-bar rigidity, body-hinge rigidity, and rigidity on surfaces of revolution. In addition, we use computational methods to determine which Ramanujan graphs of small order are globally rigid in $\mathbb{R}^2$.
Connectivity, 52C25 (Primary) 05C50, Eigenvalues, singular values, and eigenvectors, Graphs and linear algebra (matrices, eigenvalues, etc.), global rigidity, 004, 510, rigidity, redundant rigidity, 52C25 (Primary) 05C50, 05C40 (Secondary), Rigidity and flexibility of structures (aspects of discrete geometry), connectivity, algebraic connectivity, FOS: Mathematics, eigenvalue, Mathematics - Combinatorics, Combinatorics (math.CO), math.CO, 05C40 (Secondary)
Connectivity, 52C25 (Primary) 05C50, Eigenvalues, singular values, and eigenvectors, Graphs and linear algebra (matrices, eigenvalues, etc.), global rigidity, 004, 510, rigidity, redundant rigidity, 52C25 (Primary) 05C50, 05C40 (Secondary), Rigidity and flexibility of structures (aspects of discrete geometry), connectivity, algebraic connectivity, FOS: Mathematics, eigenvalue, Mathematics - Combinatorics, Combinatorics (math.CO), math.CO, 05C40 (Secondary)
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