摘 要: | Synopsis As a remark on [1], it is pointed out that C~2 solutions of u_(tt)-sum from to n=1 to 3(u_(x_4x_4))=u_t~2 with compact supported initial data must vanish everywhere in R_+~4. A remark on Fritz John's paper [1] is given in this paper. In[2],a remarkable result is obtained that the Cauchy problem for nonlinear wave euation with small initial data always has global solution if the space dimension≥6.For the on-dimensional wave equation,the situation is just the
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