Academy of Mathematics and Systems Science, CAS Colloquia & Seminars | Speaker: | 姜子麟 博士,Arizona State University | Inviter: | | Title: | Forbidden subgraphs and spherical two-distance sets | Time & Venue: | 2021.07.27 10:00-11:30 腾讯会议:225 342 754 | Abstract: | A set of unit vectors in a Euclidean space is called a spherical two-distance set if the pairwise inner products of these vectors assume only two values α>β. It is known that the maximum size of a spherical two-distance grows quadratically as the dimension of the Euclidean space grows. However when the values α and β are held fixed, a very intricate behavior of the maximum size emerges. Building on our recent resolution in the equiangular case, that is α+β=0, we make a plausible conjecture which connects this behavior with spectral theory of signed graphs in the regime β<0<α, and we confirm this conjecture when α+2β<0 or (1?α)/(β?α) < 2.0198. Joint work with Alexandr Polyanskii, Jonathan Tidor, Yuan Yao, Shengtong Zhang and Yufei Zhao. | | | |