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A remark on functions continuous on all lines

Luděk Zajíček (2019)

Commentationes Mathematicae Universitatis Carolinae

We prove that each linearly continuous function f on n (i.e., each function continuous on all lines) belongs to the first Baire class, which answers a problem formulated by K. C. Ciesielski and D. Miller (2016). The same result holds also for f on an arbitrary Banach space X , if f has moreover the Baire property. We also prove (extending a known finite-dimensional result) that such f on a separable X is continuous at all points outside a first category set which is also null in any usual sense.

Affine group acting on hyperspaces of compact convex subsets of ℝⁿ

Sergey A. Antonyan, Natalia Jonard-Pérez (2013)

Fundamenta Mathematicae

For every n ≥ 2, let cc(ℝⁿ) denote the hyperspace of all nonempty compact convex subsets of the Euclidean space ℝⁿ endowed with the Hausdorff metric topology. Let cb(ℝⁿ) be the subset of cc(ℝⁿ) consisting of all compact convex bodies. In this paper we discover several fundamental properties of the natural action of the affine group Aff(n) on cb(ℝⁿ). We prove that the space E(n) of all n-dimensional ellipsoids is an Aff(n)-equivariant retract of cb(ℝⁿ). This is applied to show that cb(ℝⁿ) is homeomorphic...

Algunos resultados sobre sistemas de desigualdades lineales.

Juan Antonio Mira López (1988)

Trabajos de Investigación Operativa

En este artículo aplicamos la condición de Mazur-Orlicz para extender a espacios normados algunos resultados de consistencia de desigualdades lineales (s.d.l.) en Rn. Asimismo, obtenemos condiciones para la consistencia de s.d.l. en un espacio localmente convexo, cuando las soluciones pertenecen a ciertos subconjuntos del dual topológico.

An extension of Lorentz's almost convergence and applications in Banach spaces

Mercourakis, S., Vassiliadis, G. (2006)

Serdica Mathematical Journal

2000 Mathematics Subject Classification: Primary 40C99, 46B99.We investigate an extension of the almost convergence of G. G. Lorentz requiring that the means of a bounded sequence converge uniformly on a subset M of N. We also present examples of sequences α∈ l∞(N) whose sequences of translates (Tn α)n≥ 0 (where T is the left-shift operator on l∞(N)) satisfy: (a) Tn α, n ≥ 0 generates a subspace E(α) of l∞(N) that is isomorphically embedded into c0 while α is not almost convergent. (b) Tn...

Antiproximinal sets in the Banach space c ( X )

S. Cobzaş (1997)

Commentationes Mathematicae Universitatis Carolinae

If X is a Banach space then the Banach space c ( X ) of all X -valued convergent sequences contains a nonvoid bounded closed convex body V such that no point in C ( X ) V has a nearest point in V .

Currently displaying 21 – 40 of 302