## Existence and uniqueness of initial value problems for a class of second- order differential equations.(English)Zbl 0691.34005

The authors investigate the initial value problem for the second order differential equations of the form (1) $$x''(t)=g(x(t),x'(t),x''(t)),$$ which cannot be solved for the highest order derivative. Their work is related to that of Petryshyn who used the theory of A-mappings. The authors’ investigations arise from a global bifurcation result for an A- proper operator, where some of the possible behaviour of a global bifurcation can be eliminated if the corresponding initial value problem has a unique solution. The authors claim that if g is Lipschitz in all variables with Lipschitz constant I in the third variable, then solutions of the initial value problem are not unique as it might be expected.
The authors prove in section 2 that the solution can be modified on a set of measure zero so that $$x''$$ is continuous while in section 3 they give an example to illustrate the theorem proved in this section namely. If $$g(0,0,0)=0$$ and the initial date is taken to be zero, then 0 is always a solution of the initial value problem $$x''=g(x,x',x''),$$ $$x(0)=A=0$$, $$x'(0)=B=0$$ which is written as the equation $$Lx=Nx$$, $$x\in X$$ where $$L,N: X\to Y$$ are given by $$Lx=x''$$, $$Nx(t)=g(x(t),x'(t),x''(t)).$$
Reviewer: F.M.Ragab

### MSC:

 34A12 Initial value problems, existence, uniqueness, continuous dependence and continuation of solutions to ordinary differential equations 65L05 Numerical methods for initial value problems involving ordinary differential equations

### Keywords:

A-mappings; global bifurcation
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### References:

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