Narrow Results

The existence of essential fixed points is proved for compact self-maps of arbitrary absolute neighborhood retracts, provided the generalized Lefschetz number is nontrivial and the topological dimension of a fixed point set is equal to zero. Furthermore, continuous self-maps of some special compact absolute neighborhood retracts, whose Lefschetz number is nontrivial, are shown to possess pseudo-essential fixed points even without the zero dimensionality assumption. Both results are applied to the existence of essential and pseudo-essential multivalued fractals. An illustrative example of this application is supplied.

Two deterministic Sharkovsky-type theorems on the circle due to L. Block [Proc. Amer. Math. Soc.82 (1981) 481–486] and X. Zhao [Fixed Point Theory Appl., Article ID 194875 (2008)] are randomized. The randomization of Block’s theorem brings an additional information about the forcing alternatives. Some further possibilities of the randomized Zhao’s theorem are discussed for multivalued maps.

Our randomized versions of the Sharkovsky-type cycle coexistence theorems on tori and, in particular, on the circle are applied to random impulsive differential equations and inclusions. The obtained effective coexistence criteria for random subharmonics with various periods are formulated in terms of the Lefschetz numbers (in dimension one, in terms of degrees) of the impulsive maps and their iterates w.r.t. the (deterministic) state variables. Otherwise, the forcing properties of certain periods of the given random subharmonics are employed, provided there exists a random harmonic solution. In the single-valued case, the exhibition of deterministic chaos in the sense of Devaney is detected for random impulsive differential equations on the factor space $ℝ/\mathbb{Z}$. Several simple illustrative examples are supplied.