Andreas Blass’s primary field of research is set theory, but he has also worked in other branches of logic (including recursion theory and topos theory), in theoretical computer science, and in finite combinatorics. Amid many excursions to other areas, he has always returned to ultrafilters, especially the combinatorial properties of ultrafilters on the natural numbers.

He received his Ph.D. from Harvard University in 1970, under the supervision of Frank Wattenberg, and he has been at the University of Michigan ever since, except for sabbaticals at Wisconsin, Penn State, and now the Fields Institute. For each of the last 10 years, he has spent part or all of the summer as a visiting researcher at Microsoft Research.

Personal website


Recent and upcoming talks by Andreas Blass

Andreas Blass: The Tukey ordering and ultrafilters

Thursday, April 07, 2016, 4:00pm-5:30pm, at 2866 East Hall. The Tukey ordering is a relation between directed partial orders. It was introduced for topological purposes, dealing with limits and accumulation points of nets. continue reading…

Alan Dow Conference, December 6–9, 2014

60 years of Dow celebrating the mathematics of Alan Dow December 6–9, 2014 Alan Dow has made deep contributions to set-theoretic topology and has been one of few researchers to pioneer new techniques in set theory which were directly motivated by fundamental topological problems. continue reading…

Set Theory Workshop in Freiburg, June 10 – 13, 2014

Set Theory Workshop in Freiburg at FRIAS and the Mathematical Institute of the Albert-Ludwigs-Universität June 10 – 13, 2014 About recent topics in set theory Speakers include Alessandro Andretta, Turin Andreas Blass, Ann Arbor Natasha Dobrinen, Denver Mirna Džamonja, Norwich Vera Fischer, Vienna Sy-David Friedman, Vienna Martin Goldstern, Vienna Menachem Kojman, Beer Sheva Péter Komjáth, Budapest Giorgio Laguzzi, Hamburg Adrian Mathias, La Réunion Menachem Magidor, Jerusalem Janusz Pawlikowski, Wrocław Lajos Soukup, Budapest Stevo Todorčević, Paris and Toronto Boban Veličković, Paris Matteo Viale, Turin Philip Welch, Bristol Lyubomyr Zdomskyy, Vienna Organisers: Heike Mildenberger, Freiburg  Luca Motto Ros, Freiburg continue reading…

Ramsey theory conference, May 24 – 28, 2014

Ramsey theory conference, University of Denver. May 24–28, 2014 The aim of this conference is to bring together students and researchers from around the world in the field of Ramsey Theory. continue reading…

INFTY Final Conference, March 4-7 2014

The INFTY Final Conference marks the conclusion of the European Science Foundation Research Networking Programme INFTY – New frontiers of infinity: mathematical, philosophical, and computational prospects. The INFTY network is devoted to the study of a wide range of aspects of Infinity. continue reading…

Andreas Blass: The next best thing to a P-point

21/Sep/2012, 13:30–15:00 Fields institute,Room 210 Speaker: Andreas Blass Title: The next best thing to a P-point Abstract: I’ll present a couple of examples of ultrafilters that are not P-points but have the strongest weak (i.e., square-bracket, exponent 2) partition property that is possible for non-P-points.  continue reading…

Andreas Blass: Partition Theorems and Ultrafilters Part 5

Monday, April 16, 2012, from 4 to 5:30pm East Hall, room 2866 Speaker: Andreas Blass (University of Michigan) Title: Partition Theorems and Ultrafilters Part 4 Abstract: I’ll discuss a forcing notion that adjoins an ultrafilter that (1) is not a P-point, (2) has the strongest square-bracket partition property consistent with not being a P-point, and (3) is not a sum of other ultrafilters. continue reading…

Andreas Blass: Partition Theorems and Ultrafilters Part 4

Monday, April 9, 2012, from 4 to 5:30pm East Hall, room 2866 Speaker: Andreas Blass (University of Michigan) Title: Ultrafilters and Partition Relations Abstract: I’ll finish the proof of the partition theorem for selective-indexed sums of non-isomorphic selective ultrafilters. continue reading…

Andreas Blass: Partition Theorems and Ultrafilters Part 3

Monday, April 2, 2012, from 4 to 5:30pm East Hall, room 2866 Speaker: Andreas Blass (University of Michigan) Title: Ultrafilters and Partition Theorems Abstract: I’ll continue the series of talks on partition theorems and ultrafilters. continue reading…

Andreas Blass: Partition Theorems and Ultrafilters Part 2

Monday, March 19, 2012, from 4 to 5:30pm East Hall, room 2866 Speaker: Andreas Blass (University of Michigan) Title: Partition Theorems and Ultrafilters Part 2 Abstract: I’ll continue to speak on “Partition theorems and ultrafilters”. continue reading…