Theorems on continuous dependence of the fixed point on parameter and applications to differential equations in locally convex spaces


Olga Hadžić




In this paper some theorems on continuous dependence of the fixed point on a parameter are proved. As applications, the following result was obtained. \emph{Theorem 5. Let $\wedge$ be a topological spave, $f(x,t,\lambda)$ be a continuous mapping $E\times[t_0-a,t_0+a]\times\wedge$ in $E$, and $\lambda\to x_0(\lambda)$ continuous mapping $\wedge$ in $E$. Let for every $\lambda\in\wedge$ the mapping $f(x,t,\lambda)$ satisfy the following conditions:} \emph{1. For every $\alpha\in I$ there exists $k_\alpha(t,\lambda)$, integrable over $[t_0-a,\;t_0\neq a]$, so that:} \[ |f(x,t,ambda)-f(y,t,ambda)|lphaeq k_lpha(t,ambda)|x-y|ǎrphi_ambda(lpha)\quad x,yı E,\;tı I. \] \emph{2. There exists $h'>0$, natural number $n_\alpha$, and positive constants $A(\alpha)$ and $Q(\alpha)$ independents of $\alpha$, so that:} \[ a)\quad\max\Big(ıt_{t_0-h'}^{t_0}kǎrphi^n_ambda(lpha)(t,ambda)dt,\;ıt_{t_0}^{t_0+h'}kǎrphi^n_ambda(lpha)(t,ambda)dt\Big)eq A(lpha),\quad n<n_lpha \] \[ a)\quad\max\Big(ıt_{t_0-h'}^{t_0}kǎrphi^n_ambda(lpha)(t,ambda)dt,\;{ıt'}_{t_0}^{t_0+h}kǎrphi^n_ambda(lpha)(t,ambda)dt\Big)eq Q(lpha)<1,\quad n\geq n_lpha \] \emph{3. For every $\alpha\in I$, there exists $\beta(\alpha)\in I$ and $m_\alpha>0$ independent of $\lambda$, so that:} \[ |x|ǎrphi^n_ambda(lpha)eq m_lpha|x|\beta(lpha)\quad xı E \] \emph{Then: $(t,\lambda)\to x(t,\lambda)$ is a continuous mapping $[t_0-h,\;t_0+h]\times\wedge$ in $E$, where $x(t,\lambda)$ is the solution of the differential equation \[ \frac{dx}{dt}=f(x,t,ambda)\quad x(t_0)=x_0(ambda) \] defined in $I'=[t_0-h,\;t_0+h],\quad h=\min(a,h')$.}