The pcf-theorem revisited
Logic
2009-09-25 v1
Abstract
The pcf theorem (of the possible cofinality theory) was proved for reduced products prod_{i< kappa} lambda_i/I, where kappa < min_{i< kappa} lambda_i. Here we prove this theorem under weaker assumptions such as wsat(I)< min_{i< kappa} lambda_i, where wsat(I) is the minimal theta such that kappa cannot be delivered to theta sets notin I (or even slightly weaker condition). We also look at the existence of exact upper bounds relative to <_I (<_I-eub) as well as cardinalities of reduced products and the cardinals T_D(lambda). Finally we apply this to the problem of the depth of ultraproducts (and reduced products) of Boolean algebras
Cite
@article{arxiv.math/9502233,
title = {The pcf-theorem revisited},
author = {Saharon Shelah},
journal= {arXiv preprint arXiv:math/9502233},
year = {2009}
}