TY - JOUR T1 - Orbital Instability of Standing Waves for the Coupled Nonlinear Klein-Gordon Equations JO - Journal of Partial Differential Equations VL - 4 SP - 303 EP - 314 PY - 2008 DA - 2008/11 SN - 21 DO - http://doi.org/ UR - https://global-sci.org/intro/article_detail/jpde/5284.html KW - Orbital instability KW - standing wave KW - coupled Klein-Gordon equations KW - invariant set AB - This paper deals with a type of standing waves for the coupled nonlinear Klein-Gordon equations in three space dimensions. First we construct a suitable constrained variational problem and obtain the existence of the standing waves with ground state by using variational argument. Then we prove the orbital instability of the standing waves by defining invariant sets and applying some priori estimates.