Existence and uniqueness of initial value problems for a class of second- order differential equations
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 \(Lx=x''\), \(Nx(t)=g(x(t),x'(t),x''(t)).\)
scientific article; zbMATH DE number 4130775