利用变分原理和Z2不变群指标研究二阶泛函微分方程:(a(t)x′(t-τ))′-b(t)x(t)+fλ(t,x(t),x(t-)τ,x(t-2τ))=0的多重周期解,得出相关结果。
By means of variational structure and Z2 group index theory, we obtain the existence of multiple periodic solutions to second--order functional differential equations (a(t)x′(t-τ))′-b(t)x(t)+fλ(t,x(t),x(t-)τ,x(t-2τ))=0.