English

An orthogonal relation on inverse cyclotomic polynomials

Number Theory 2022-08-31 v1

Abstract

Let Φn(X)\Phi_n(X) and Ψn(X)=Xn1Φn(X)\Psi_n(X)=\frac{X^{n}-1}{\Phi_{n}(X)} be the nn-th cyclotomic and inverse cyclotomic polynomials respectively. In this short note, for any pair of divisors d1d2 d_{1} \neq d_{2} of n n , and integers l1l_1 and l2l_2 such that 0l1φ(d1)1 0 \leq l_{1} \leq \varphi(d_{1})-1 and 0l2φ(d2)1 0 \leq l_{2} \leq \varphi(d_{2})-1 , we show that Xl1Ψd1(X)(1+Xd1+Xnd1),Xl2Ψd2(X)(1+Xd2+Xnd2)=0,\left \langle X^{l_{1}} \Psi_{d_{1}}(X) (1+X^{d_1}+\dots X^{n-d_1}), X^{l_{2}} \Psi_{d_{2}}(X) (1+X^{d_2}+\dots X^{n-d_2}) \right \rangle =0, where , \langle \cdot, \cdot \rangle is the inner product on Q[X]\mathbb{Q}[X] defined by kakXk,kbkXk=kakbk \langle \sum_{k} a_{k}X^{k},\sum_{k} b_{k}X^{k} \rangle =\sum_{k} a_{k}b_{k}.

Keywords

Cite

@article{arxiv.2208.14147,
  title  = {An orthogonal relation on inverse cyclotomic polynomials},
  author = {Jianfeng Xie},
  journal= {arXiv preprint arXiv:2208.14147},
  year   = {2022}
}
R2 v1 2026-06-25T02:05:07.183Z