36 citations · 51 across the 4 of their papers we have counts for
5 papers
Automorphism groups and uniqueness of holomorphic vertex operator algebras of central charge
Koichi Betsumiya, Ching Hung Lam, Hiroki Shimakura
We describe the automorphism groups of all holomorphic vertex operator algebras of central charge with non-trivial weight one Lie algebras by using their constructions as simp…
Automorphism groups of cyclic orbifold vertex operator algebras associated with the Leech lattice and some non-prime isometries
Koichi Betsumiya, Ching Hung Lam, Hiroki Shimakura
We determine the automorphism groups of the cyclic orbifold vertex operator algebras associated with coinvariant lattices of isometries of the Leech lattice in the conjugacy classe…
Upper bounds on cyclotomic numbers
Koichi Betsumiya, Mitsugu Hirasaka, Takao Komatsu +1
In this article, we give upper bounds for cyclotomic numbers of order e over a finite field with q elements, where e is a divisor of q-1. In particular, we show that under certain…
A complete classification of doubly even self-dual codes of length 40
Koichi Betsumiya, Masaaki Harada, Akihiro Munemasa
A complete classification of binary doubly even self-dual codes of length 40 is given. As a consequence, a classification of binary extremal self-dual codes of length 38 is also gi…
On triply even binary codes
Koichi Betsumiya, Akihiro Munemasa
A triply even code is a binary linear code in which the weight of every codeword is divisible by 8. We show how two doubly even codes of lengths m_1 and m_2 can be combined to make…