Jech–Kunen tree

A Jech–Kunen tree is a set-theoretic tree with properties that are incompatible with the generalized continuum hypothesis. It is named after Thomas Jech and Kenneth Kunen, both of whom studied the possibility and consequences of its existence.

Definition
A ω1-tree is a tree with cardinality $$\aleph_1$$ and height ω1, where ω1 is the first uncountable ordinal and $$\aleph_1$$ is the associated cardinal number. A Jech–Kunen tree is a ω1-tree in which the number of branches is greater than $$\aleph_1$$ and less than $$2^{\aleph_1}$$.

Existence
found the first model in which this tree exists, and showed that, assuming the continuum hypothesis and $$2^{\aleph_1} > \aleph_2$$, the existence of a Jech–Kunen tree is equivalent to the existence of a compact Hausdorff space with weight $$\aleph_1$$ and cardinality strictly between $$\aleph_1$$ and  $$2^{\aleph_1}$$.