10 citations · 21 across the 14 of their papers we have counts for
23 papers
Erratum and a counterexample to: Stability of diametral diameter two properties
Johann Langemets
In Proposition 3.5 of our paper [J. Langemets and K. Pirk, Stability of diametral diameter two properties, RACSAM (2021)], we claimed that the convex DLD2P lifts from an -ideal…
Characterizing the Daugavet property by squares of rank-one operators
Johann Langemets
We prove that, for real Banach spaces of dimension greater than one, each of the identities and , required for every rank-one operator…
Dual Banach spaces with the ball-covering property
Johann Langemets, Emma Mõttus, Natalia Saealle
We study ball-covering properties of dual Banach spaces and their connections with the geometry of predual unit balls. One of our main results shows that, for every separable Banac…
Transfinite Daugavet property
Antonio Avilés, Johann Langemets, Miguel Martín +1
We extend the Daugavet property and a perfect version of it to transfinite cardinals in order to distinguish between spaces with the ordinary Daugavet property by some kind of comp…
The super Alternative Daugavet property for Banach spaces
Johann Langemets, Marcus Lõo, Miguel Martín +2
We introduce the super alternative Daugavet property (super ADP) which lies strictly between the Daugavet property and the Alternative Daugavet property as follows. A Banach space…
Slicely countably determined points in Banach spaces
Johann Langemets, Marcus Lõo, Miguel Martin +1
We introduce slicely countably determined points (SCD points) of a bounded and convex subset of a Banach space which extends the notions of denting points, strongly regular points…
Unconditional bases and Daugavet renormings
Rainis Haller, Johann Langemets, Yoël Perreau +1
We introduce a new diametral notion for points of the unit sphere of Banach spaces, that naturally complements the notion of Delta-points, but is weaker than the notion of Daugavet…
Transfinite almost square Banach spaces
Antonio Avilés, Stefano Ciaci, Johann Langemets +2
It is known that a Banach space contains an isomorphic copy of if, and only if, it can be equivalently renormed to be almost square. We introduce and study transfinite versio…
Attaining strong diameter two property for infinite cardinals
Stefano Ciaci, Johann Langemets, Aleksei Lissitsin
We extend the (attaining of) strong diameter two property to infinite cardinals. In particular, a Banach space has the 1-norming attaining strong diameter two property with respect…
A characterization of Banach spaces containing via ball-covering properties
Stefano Ciaci, Johann Langemets, Aleksei Lissitsin
In 1989, G. Godefroy proved that a Banach space contains an isomorphic copy of if and only if it can be equivalently renormed to be octahedral. It is known that octahedral…
Stability of diametral diameter two properties
Johann Langemets, Katriin Pirk
We prove that the diametral diameter two properties are inherited by -ideals (e.g., -ideals). On the other hand, these properties are lifted from an -ideal to the superspa…
On Daugavet indices of thickness
Rainis Haller, Johann Langemets, Vegard Lima +2
Inspired by R. Whitley's thickness index the last named author recently introduced the Daugavet index of thickness of Banach spaces. We continue the investigation of the behavior o…
Symmetric strong diameter two property in tensor products of Banach spaces
Johann Langemets
We continue the investigation of the behaviour of diameter two properties in tensor products of Banach spaces. Our main result shows that the symmetric strong diameter two property…
Octahedral norms in duals and biduals of Lipschitz-free spaces
Johann Langemets, Abraham Rueda Zoca
We continue with the study of octahedral norms in the context of spaces of Lipschitz functions and in their duals. First, we prove that the norm of is octahedr…
Bidual octahedral renormings and strong regularity in Banach spaces
Johann Langemets, Ginés López-Pérez
We prove that every separable Banach space containing can be equivalently renormed so that its bidual space is octahedral, which answers, in the separable case, a question…
Symmetric strong diameter two property
Rainis Haller, Johann Langemets, Vegard Lima +1
We study Banach spaces with the property that, given a finite number of slices of the unit ball, there exists a direction such that all these slices contain a line segment of lengt…
Stability of average roughness, octahedrality, and strong diameter 2 properties of Banach spaces with respect to absolute sums
Rainis Haller, Johann Langemets, Rihhard Nadel
We prove that, if Banach spaces and are -average rough, then their direct sum with respect to an absolute norm is -average rough. In particular, for octahe…
Rough norms in spaces of operators
Rainis Haller, Johann Langemets, Märt Põldvere
We investigate sufficient and necessary conditions for the space of bounded linear operators between two Banach spaces to be rough or average rough. Our main result is that $\mathc…
Almost square and octahedral norms in tensor products of Banach spaces
Johann Langemets, Vegard Lima, Abraham Rueda Zoca
The aim of this note is to study some geometrical properties like diameter two properties, octahedrality and almost squareness in the setting of (symmetric) tensor product spaces.…
On thickness and thinness of Banach spaces
Trond A. Abrahamsen, Johann Langemets, Vegard Lima +1
The aim of this note is to complement and extend some recent results on Whitley's indices of thinness and thickness in three main directions. Firstly, we investigate both the indic…
Almost square Banach spaces
Trond A. Abrahamsen, Johann Langemets, Vegard Lima
We single out and study a natural class of Banach spaces -- almost square Banach spaces. In an almost square space we can find, given a finite set in the unit…
Geometry of Banach spaces with an octahedral norm
Rainis Haller, Johann Langemets
We discuss the geometry of Banach spaces whose norm is octahedral or, more generally, locally or weakly octahedral. Our main results characterize these spaces in terms of covering…
On duality of diameter 2 properties
Rainis Haller, Johann Langemets, Märt Põldvere
It is known that a Banach space has the strong diameter 2 property (i.e. every convex combination of slices of the unit ball has diameter 2) if and only if the norm on its dual spa…