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math.FA2023★ 1 cited
Winding number criterion for the origin to belong to the numerical range of a matrix on a loop of matrices
Cheng Guo, Shanhui Fan
Let be continuous with , thus the winding number of is well-defined. If the winding number is not divisible by , then the origi…
physics.optics2023
Topological nature of non-Hermitian degenerate bands in structural parameter space
Olivia Y. Long, Cheng Guo, Shanhui Fan
In photonics, band degeneracies at high-symmetry points in wavevector space have been shown to exhibit rich physical phenomena. However, obtaining degenerate bands away from such p…