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Evasion and Prediction II
Author(s) -
Brendle Jörg,
Shelah Saharon
Publication year - 1996
Publication title -
journal of the london mathematical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.441
H-Index - 62
eISSN - 1469-7750
pISSN - 0024-6107
DOI - 10.1112/jlms/53.1.19
Subject(s) - phenomenon , homomorphism , mathematics , consistency (knowledge bases) , combinatorics , evasion (ethics) , group (periodic table) , discrete mathematics , physics , immune system , immunology , quantum mechanics , biology
A subgroup G ⩽ Z ω exhibits the Specker phenomenon if every homomorphism G → Z maps almost all unit vectors to 0. We give several combinatorial characterizations of the cardinal e, the size of the smallest G ⩽ Z ω exhibiting the Specker phenomenon. We also prove the consistency of > e, where is the unbounding number and e the evasion number. Our results answer several questions addressed by Blass.