L. Halbeisen

activity

19932025

most citedHalfway New Cardinal Characteristics

4 citations · 8 across the 23 of their papers we have counts for

collaborators

Showing math.LOShow all

16 papers · 1 filter

math.LO2025

There may be exactly $n$ $Q$ -points

Lorenz Halbeisen, Silvan Horvath, Tan Özalp

We generalize the main result of arXiv:2505.17960 and show the consistency of the statement ``There are exactly $n$ $Q$ -points up to isomorphism" for any finite $n$ . Furthermore, w…

math.LO2025

A unique $Q$ -point and infinitely many near-coherence classes of ultrafilters

Lorenz Halbeisen, Silvan Horvath, Saharon Shelah

We show that in the model obtained by iteratively pseudo-intersecting a Ramsey ultrafilter via a length- $ω_{2}$ countable support iteration of restricted Mathias forcing over a groun…

math.LO2023

Implications of Ramsey Choice Principles in ZF

Lorenz Halbeisen, Riccardo Plati, Saharon Shelah

The Ramsey Choice principle for families of $n$ -element sets, denoted $RC_{n}$ , states that every infinite set $X$ has an infinite subset $Y \subseteq X$ with a choice functi…

math.LO2021

Four Cardinals and Their Relations in ZF

Lorenz Halbeisen, Riccardo Plati, Salome Schumacher +1

For a set $M$ , $fin (M)$ denotes the set of all finite subsets of $M$ , $M^{2}$ denotes the Cartesian product $M \times M$ , $[M]^{2}$ denotes the set of all $2$ -element sub…

math.LO2021

A New Weak Choice Principle

Lorenz Halbeisen, Riccardo Plati, Salome Schumacher

For every natural number $n$ we introduce a new weak choice principle $nR C_{fin}$ : Given any infinite set $x$ , there is an infinite subset $y \subseteq x$ and a selection f…

math.LO2021

Some implications of Ramsey Choice for n-element sets

Lorenz Halbeisen, Salome Schumacher

Let $n \in ω$ . The weak choice principle $RC_{n}$ states that for every infinite set $x$ there is an infinite subset $y \subseteq x$ with a choice function on $[y]^n:=\{z…

There may be exactly n Q-points

A unique Q-point and infinitely many near-coherence classes of ultrafilters

Implications of Ramsey Choice Principles in ZF

Four Cardinals and Their Relations in ZF

A New Weak Choice Principle

Some implications of Ramsey Choice for n-element sets

There may be exactly $n$ $Q$ -points

A unique $Q$ -point and infinitely many near-coherence classes of ultrafilters