1,721,098 research outputs found
A nonautonomous nonlinear functional differential equation arising in the theory of population dynamics
No full textAbstractA nonlinear periodic functional differential equation with unbounded delay describing the growth of a single species with depensation is considered. The global bifurcation of positive periodic solutions from the null one is studied and the differences from logistic-type equations are shown, namely the multiplicity of non-trivial solutions and the occurrence of a new bifurcation phenomenon. The biological meaning of the results is discussed
An equation of growth of a single species with realistic dependence on crowding and seasonal factors.
No full textGeometric properties of solutions of Hamilton-Jacobi equations
No full textAbstractThe method of moving parallel planes, previously used for elliptic and parabolic PDE, is adapted to study solutions of the Cauchy problem for Hamilton-Jacobi equations. This is possible in the framework of the theory of viscosity solutions, using the comparison theorem for such solutions as a kind of maximum principle. One of the main results states that if the initial data are nonnegative and compact supported, the Hamiltonian radial and the level sets expanding, then the level sets become asymptotically spherical as t → ∞, the convergence taking place in the Lipschitz norm
Almost sure stabilizability of controlled degenerate diffusions
Full text linkWe develop a direct Lyapunov method for the almost sure open-loop stabilizability and asymptotic stabilizability of controlled degenerate diffusion processes. The infinitesimal decrease condition for a Lyapunov function is a new form of Hamilton–Jacobi–Bellman partial differential inequality of second order. We give local and global versions of the first and second Lyapunov theorems, assuming the existence of a lower semicontinuous Lyapunov function satisfying such an inequality in the viscosity sense. An explicit formula for a stabilizing feedback is provided for affine systems with smooth Lyapunov function. Several examples illustrate the theory
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