Oscillation theorems for certain third order nonlinear delay dynamic equations on time scales

摘要

In this paper, we establish some new oscillation criteria for the third order nonlinear delay dynamic equations $$left(b(t)left([a(t)(x^Delta(t))^{lpha_1}]^Deltaight)^{lpha_2}ight)^Delta+q(t)x^{lpha_3}(au(t))=0$$ on a time scale $mathbb{T}$, where $lpha_i$ are ratios of positive odd integers, $i=1, 2, 3,$ $b, a$ and $q$ are positive real-valued rd-continuous functions defined on $mathbb{T}$, and the so-called delay function $au:mathbb{T}ightarrow mathbb{T}$ is a strictly increasing function such that $au(t)leq t$ for $tin mathbb{T}$ and $au(t)ightarrowinfty$ as $tightarrowinfty.$ By using the Riccati transformation technique and integral averaging technique, some new sufficient conditions which insure that every solution oscillates or tends to zero are established. Our results are new for third order nonlinear delay dynamic equations and complement the results established by Yu and Wang in J. Comput. Appl. Math., 2009, and Erbe, Peterson and Saker in J. Comput. Appl. Math., 2005. Some examples are given here to illustrate our main results.