Semilinear wave equation;
Klein-Gordon equation;
multiple propagation speeds;
null condition;
weak null condition;
global existence;
KLEIN-GORDON EQUATIONS;
GLOBAL EXISTENCE;
NONLINEAR-WAVE;
HYPERBOLIC SYSTEMS;
ENERGY DECAY;
D O I:
10.14492/hokmj/2022-637
中图分类号:
O1 [数学];
学科分类号:
0701 ;
070101 ;
摘要:
We consider the Cauchy problems for systems of nonlinear wave and Klein -Gordon equations, or for systems of nonlinear wave equations with multiple propagation speeds in three space dimensions. Global existence of solutions under the so-called null condition is already known for these systems. Our aim here is to obtain the global existence for these systems with some kinds of nonlinearities violating the null condition.