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Topology and dynamics of unstable attractors

M. A. Morón, J. J. Sánchez-Gabites, J. M. R. Sanjurjo (2007)

Fundamenta Mathematicae

This article aims to explore the theory of unstable attractors with topological tools. A short topological analysis of the isolating blocks for unstable attractors with no external explosions leads quickly to sharp results about their shapes and some hints on how Conley's index is related to stability. Then the setting is specialized to the case of flows in ℝⁿ, where unstable attractors are seen to be dynamically complex since they must have external explosions.

Topology of the isometry group of the Urysohn space

Julien Melleray (2010)

Fundamenta Mathematicae

Using classical results of infinite-dimensional geometry, we show that the isometry group of the Urysohn space, endowed with its usual Polish group topology, is homeomorphic to the separable Hilbert space ℓ²(ℕ). The proof is based on a lemma about extensions of metric spaces by finite metric spaces, which we also use to investigate (answering a question of I. Goldbring) the relationship, when A,B are finite subsets of the Urysohn space, between the group of isometries fixing A pointwise, the group...

Topology on ordered fields

Yoshio Tanaka (2012)

Commentationes Mathematicae Universitatis Carolinae

An ordered field is a field which has a linear order and the order topology by this order. For a subfield F of an ordered field, we give characterizations for F to be Dedekind-complete or Archimedean in terms of the order topology and the subspace topology on F .

Trajectories, first return limiting notions and rings of H -connected and iteratively H -connected functions

Ewa Korczak-Kubiak, Ryszard J. Pawlak (2013)

Czechoslovak Mathematical Journal

In the paper the existing results concerning a special kind of trajectories and the theory of first return continuous functions connected with them are used to examine some algebraic properties of classes of functions. To that end we define a new class of functions (denoted C o n n * ) contained between the families (widely described in literature) of Darboux Baire 1 functions ( DB 1 ) and connectivity functions ( C o n n ). The solutions to our problems are based, among other, on the suitable construction of the ring,...

Trajectory of the turning point is dense for a co-σ-porous set of tent maps

Karen Brucks, Zoltán Buczolich (2000)

Fundamenta Mathematicae

It is known that for almost every (with respect to Lebesgue measure) a ∈ [√2,2] the forward trajectory of the turning point of the tent map T a with slope a is dense in the interval of transitivity of T a . We prove that the complement of this set of parameters of full measure is σ-porous.

Transfinite inductions producing coanalytic sets

Zoltán Vidnyánszky (2014)

Fundamenta Mathematicae

A. Miller proved the consistent existence of a coanalytic two-point set, Hamel basis and MAD family. In these cases the classical transfinite induction can be modified to produce a coanalytic set. We generalize his result formulating a condition which can be easily applied in such situations. We reprove the classical results and as a new application we show that consistently there exists an uncountable coanalytic subset of the plane that intersects every C¹ curve in a countable set.

Transitive flows on manifolds.

Víctor Jiménez López, Gabriel Soler López (2004)

Revista Matemática Iberoamericana

In this paper we characterize manifolds (topological or smooth, compact or not, with or without boundary) which admit flows having a dense orbit (such manifolds and flows are called transitive) thus fully answering some questions by Smith and Thomas. Name

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