Let denote a distance-regular graph with vertex set X , diameter D ≥ 3, valency k ≥ 3, and assume supports a spin modelTo avoid degenerate situations we assume is not a Hamming graph and t i ∈ {t 0 , −t 0 } for 1 ≤ i ≤ D. In an earlier paper Curtin and Nomura determined the intersection numbers of in terms of D and two complex parameters η and q. We extend their results as follows. Fix any vertex x ∈ X and let T = T (x) denote the corresponding Terwilliger algebra. Let U denote an irreducible T -module with endpoint r and diameter d. We obtain the intersection numbers c i (U ), b i (U ), a i (U ) as rational expressions involving r, d, D, η and q. We show that the isomorphism class of U as a T -module is determined by r and d. We present a recurrence that gives the multiplicities with which the irreducible T -modules appear in the standard module. We compute these multiplicites explicitly for the irreducible T -modules with endpoint at most 3. We prove that the parameter q is real and we show that if is not bipartite, then q > 0 and η is real.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.