Title
Non-saturation of the non-stationary ideal on Pκ (λ) with λ of countable cofinality.
Abstract
Given a regular uncountable cardinal kappa and a cardinal lambda > kappa of cofinality omega, we show that the restriction of the non-stationary ideal on P-kappa(lambda) to the set of a with cf(sup(a boolean AND kappa)) = omega is not lambda(++) -saturated (and even not 2((lambda<kappa))-saturated in case 2(lambda) = lambda(+)). We actually prove the stronger result that there is Q subset of NG(kappa,lambda)(+) with |Q| - lambda(++) such that A boolean AND B is a non-cofinal subset of P-kappa(lambda) for any two distinct members A, B of Q, where NG(kappa,lambda) denotes the game ideal on P-kappa (lambda). We also remark that for kappa > omega(1), adding lambda(+3) Cohen subsets of omega(1) to L makes NG(kappa,lambda) lambda(+3)-saturated. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Year
DOI
Venue
2012
10.1002/malq.201020055
MATHEMATICAL LOGIC QUARTERLY
Keywords
Field
DocType
P?(?),saturation,MSC (2010) 03E05
Discrete mathematics,Combinatorics,Countable set,Uncountable set,Cofinality,Mathematics
Journal
Volume
Issue
ISSN
58
1-2
0942-5616
Citations 
PageRank 
References 
2
0.43
3
Authors
1
Name
Order
Citations
PageRank
Pierre Matet12911.25