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Ultrafilters on |
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| Authors: | Saharon Shelah Jö rg Brendle Saharon Shelah |
| Affiliation: | Department of Mathematics, Dartmouth College, Bradley Hall, Hanover, New Hampshire 03755 ; Institute of Mathematics, The Hebrew University, Jerusalem 91904, Israel - Department of Mathematics, Rutgers University, New Brunswick, New Jersey 08903 |
| Abstract: | For a free ultrafilter  on  we study several cardinal characteristics which describe part of the combinatorial structure of  . We provide various consistency results; e.g. we show how to force simultaneously many characters and many  -characters. We also investigate two ideals on the Baire space  naturally related to  and calculate cardinal coefficients of these ideals in terms of cardinal characteristics of the underlying ultrafilter. |
| Keywords: | Ultrafilter $P$--point Ramsey ultrafilter character $pi $--character ideal Ramsey null sets (nowhere Ramsey sets) cardinal coefficient Mathias forcing Laver forcing Easton forcing |
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