## Nagumo type condition for partial differential inclusions.(English)Zbl 0654.49016

The viability problem for autonomous differential inclusions in Hilbert and Banach spaces and for the generalized equation $$0\in F(x)$$ is studied. Let V, H be two Hilbert spaces such that $$V\subset H=H'\subset V'$$, the inclusions being compact and dense, and let $$K\subset H$$ be a closed set with the so-called internal approximation property. For the differential inclusion (1) $$\dot x+Ax\in G(x)$$, $$x(0)=x_ 0\in K$$, x(t)$$\in K$$ for all $$t\in [0,T]$$, where G: $$K\to V$$ is an upper- semicontinuous multifunction with closed convex values such that G(K) is bounded and $$A\in L(V,V')$$ is a V-elliptic operator. Under a simple generalization of the so-called tangential condition $$[G(x)-Ax]\cap T_ K'(x)\neq \emptyset$$ for all $$x\in K\cap V$$, the existence of a $$W^{1,2}(0,T)$$-solution of problem (1) is proved for all $$x_ 0\in K$$ and any $$T>0$$. The proof is based on a finite-dimensional approximation and classical results. Next, under the same assumptions the existence of solutions of the equation Ax$$\in G(x)$$ in $$K\cap V$$ is proved.
At the end some finite-difference scheme for equation (1) is proposed, and the existence of a solution of problem (1) in the space $$W^{\infty}(0,T)$$ is obtained.
As applications, the boundary and obstacle problems for parabolic differential inclusions, equations and inequalities and for variational inequalities are studied.
Reviewer: Z.Wyderka

### MSC:

 93B05 Controllability 49J45 Methods involving semicontinuity and convergence; relaxation 35K20 Initial-boundary value problems for second-order parabolic equations 35K85 Unilateral problems for linear parabolic equations and variational inequalities with linear parabolic operators 34A60 Ordinary differential inclusions 34G20 Nonlinear differential equations in abstract spaces 49J40 Variational inequalities
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