A Gregus type common fixed point theorem in normed spaces with applications.
A group automorphism is a factor of a direct product of a zero entropy automorphism and a Bernoulli automorphism
A group topology on the free abelian group of cardinality 𝔠 that makes its square countably compact
Under 𝔭 = 𝔠, we prove that it is possible to endow the free abelian group of cardinality 𝔠 with a group topology that makes its square countably compact. This answers a question posed by Madariaga-Garcia and Tomita and by Tkachenko. We also prove that there exists a Wallace semigroup (i.e., a countably compact both-sided cancellative topological semigroup which is not a topological group) whose square is countably compact. This answers a question posed by Grant.
A half-commutative IP Roth theorem.
A homological selection theorem implying a division theorem for Q-manifolds
We prove that a space M with Disjoint Disk Property is a Q-manifold if and only if M × X is a Q-manifold for some C-space X. This implies that the product M × I² of a space M with the disk is a Q-manifold if and only if M × X is a Q-manifold for some C-space X. The proof of these theorems exploits the homological characterization of Q-manifolds due to Daverman and Walsh, combined with the existence of G-stable points in C-spaces. To establish the existence of such points we prove (and afterward...
A Kirk type characterization of completeness for partial metric spaces.
A lambda-graph system for the Dyck shift and its -groups.
A Lefschetz-type coincidence theorem
A Lefschetz-type coincidence theorem for two maps f,g: X → Y from an arbitrary topological space to a manifold is given: , that is, the coincidence index is equal to the Lefschetz number. It follows that if then there is an x ∈ X such that f(x) = g(x). In particular, the theorem contains well-known coincidence results for (i) X,Y manifolds, f boundary-preserving, and (ii) Y Euclidean, f with acyclic fibres. It also implies certain fixed point results for multivalued maps with “point-like” (acyclic)...
A limit formula for regular iteration groups.
A limit formula for regular iteration groups. (Summary).
A local version of the generalized retract theorem of Ważewski with applications in the theory of partial differential equations of first order
A matrix formalism for conjugacies of higher-dimensional shifts of finite type
We develop a natural matrix formalism for state splittings and amalgamations of higher-dimensional subshifts of finite type which extends the common notion of strong shift equivalence of ℤ⁺-matrices. Using the decomposition theorem every topological conjugacy between two -shifts of finite type can thus be factorized into a finite chain of matrix transformations acting on the transition matrices of the two subshifts. Our results may be used algorithmically in computer explorations on topological...
A metatheorem for fixed point theories
-minimal sets and related topics in transformation semigroups. II.
-minimal sets and related topics in transformation semigroups. I.
A minimum theorem for n-valued multifunctions
A multi-step iterative method for approximating fixed points of Presić-Kannan operators.
A multivalued fixed point theorem in non-archimedean vector spaces.
A new class of nonexpansive type mappings and fixed points
In this paper a new class of self-mappings on metric spaces, which satisfy the nonexpensive type condition (3) below is introduced and investigated. The main result is that such mappings have a unique fixed point. Also, a remetrization theorem, which is converse to Banach contraction principle is given.
A new class of weakly countably determined Banach spaces
A class of Banach spaces, countably determined in their weak topology (hence, WCD spaces) is defined and studied; we call them strongly weakly countably determined (SWCD) Banach spaces. The main results are the following: (i) A separable Banach space not containing ℓ¹(ℕ) is SWCD if and only if it has separable dual; thus in particular, not every separable Banach space is SWCD. (ii) If K is a compact space, then the space C(K) is SWCD if and only if K is countable.