Downward closure of depth in countable Boolean algebras

作者：Kach Asher M^*; Lempp Steffen

来源：Algebra Universalis, 2012, 68(1-2): 57-74.

DOI：10.1007/s00012-012-0188-x

• Ketonen invariants
• depth
• downward closure

We study the set of depths of relative algebras of countable Boolean algebras, in particular the extent to which this set may not be downward closed within the countable ordinals for a fixed countable Boolean algebra. Doing so, we exhibit a structural difference between the class of arbitrary rank countable Boolean algebras and the class of rank one countable Boolean algebras.

• 出版日期2012-10