I am a Research Associate in statistics and mathematics at the University of Toronto.I am also one of the organizers of the Set Theory Seminar at the Fields Institute.
- I gave a talk at BFF7 about my joint paper with Dan M. Roy and Haosui Duanmu in which we characterize admissibility in statistical decision problems.
- I will teach a course on non-standard analysis with lots of applications next semester (Fall 2022). Feel free to contact me if you are interested in attending.
- Here is a 11 minute long talk I gave at the virtual ISBA 2021 conference. It is about a weaker, earlier form of the characterization of admissibility mentioned above, but still contains interesting background information.
- Here is a talk I gave at the Fields Institute Set Theory Seminar, also about admissibility, intended for an audience with a background in set theory (recorded on zoom).
- My joint paper with Karen Bakke Haga and Asger Törnquist about Maximal almost disjoint families, determinacy, and forcing has appeared in the Journal of Mathematical Logic.
- My joint paper with Sandra Müller, Philipp Schlicht, and Thilo Weinert about Lebesgue's density theorem and definable selectors for ideals has appeared in the Israel Journal of Mathematics.
My research is in mathematical logic; my primary interests are descriptive set theory, as well as infinite combinatorics, forcing, definability, and inner models. I am also interested in non-standard analysis and its applications, especially in probability theory and statistical decision theory.
- Severin Mejak (PhD, ongoing). I am co-advising Severin with Asger Törnquist.
- Karen Bakke Haga, PhD thesis, title: Maximal almost disjoint families, determinacy, and forcing. Karen defended on June 3, 2019. I co-advised her with Asger Törnquist.
- Dan Saattrup Nielsen, master thesis, title: Inner model theory. An introduction.
- I also advised bachelor projects by Magnus Baunsgaard Kristensen, Fraser Binns, and (co-advised) Dan Saattrup Nielsen (he wrote a thesis about Gödel's constructible universe).
At times, the list of papers on my arxiv author's page may be more up-to-date than the list below. The list at my arxiv page also lacks the first four items from the list below (my two theses, and two published research articles) as well as Item 11 (an article about teaching mathematics which I wrote as part of a pedadogy course at University of Copenhagen).
- Sigma^1_3-absoluteness in forcing extensions. Master's thesis, University of Vienna, 2004 (adviser: Sy Friedman).
- Lightface Sigma^1_2-indescribable cardinals. Proc. Amer. Math. Soc. 135 (2007), pp. 1213–1222.
- Projective measure without projective Baire. PhD thesis, University of Vienna, 2010 (adviser: Sy Friedman).
- (joint with Sy Friedman and Ralf Schindler) Coding over core models, in: Infinity, Computability, and Metaphysics (Geschke et al., eds.), Festschrift celebrating the 60th birthdays of Peter Koepke and Philip Welch, College Publications, pp. 167–182.
- (joint with Sy Friedman) Projective measure without projective Baire. Memoirs of the American Mathematical Society 267 (2020), no. 1298, v+150 pp..
- (joint with Asger Törnquist) Definable maximal discrete sets in forcing extensions. Math. Res. Lett. 25(5), 1591–1612, 2018.
- (joint with Asger Törnquist and Vera Fischer) A co-analytic Cohen-indestructible maximal cofinitary group. The Journal of Symbolic Logic, 82(2), 627–641.
- Definable discrete sets with large continuum. (2016) 26 pages.
- On Horowitz and Shelah's maximal eventually different family. RIMS Kyôkyûroku No. 2042, 99–105.
- Compactness of maximal eventually different families. (2017) 9 pages. Bull. London Math. Soc. 50 (2018) 340–348.
- Research-led teaching in higher mathematics. In: Improving University Science Teaching and Learning—Pedagogical Projects 2019. Department of Science Education, University of Copenhagen.
- (joint with Karen Bakke Haga and Asger Törnquist) Maximal almost disjoint families, determinacy, and forcing. Journal of Mathematical Logic. 40 pages.
- (joint with Vera Fischer) A Sacks indestructible co-analytic maximal eventually different family. Fundamenta Mathematicae, 23 pages.
- (joint with Sandra Müller, Philipp Schlicht, and Thilo Weinert) Lebesgue's density theorem and definable selectors for ideals. (2018) 28 pages. Israel Journal of Mathematics.
- (joint with Vera Fischer, Sy Friedman, and Asger Törnquist) Good projective witnesses. (April 2019) 21 pages.
- (joint with Asger Törnquist) The Ramsey property implies no mad families. Proceedings of the National Academy of Sciences, 10 pages.
- (joint with Raphaël Carroy, Benjamin Miller, and Zoltán Vidnyánsky) Minimal definable graphs of definable chromatic number at least three. Forum Math. Sigma 9 (2021), Paper No. e7.
- (joint with Vera Fischer and Thilo Weinert) Definable MAD families and forcing axioms. (December 2019) 13 pages. Annals of Pure and Applied Logic, 172 (5).
- (joint with Asger Törnquist) The Ramsey property and higher dimensional mad families. (November 2018) 29 pages. Journal of Mathematical Logic
- Maximal discrete sets. RIMS Kôkyûroku No. 2164, pp. 64–84.
- (joint with Robert M. Anderson, Haosui Duanmu, and William Weiss) Loeb extension and Loeb equivalence . Proceedings of the American Mathematical Society, Series B, Volume 8, Issue 10, 112–120.
- Constructing maximal cofinitary groups . (May 2021) 19 pages.
- (joint with Haosui Duanmu and Daniel M. Roy) Admissibility is Bayes optimality with infinitesimals.
- (joint with Haosui Duanmu and William Weiss) Loeb extension and Loeb equivalence II.
Upcoming and past talks and travel
- 2021: Novi Sad Conference in Set theory and General Topology (SETTOP), Serbia.
- September/November 2021: DMV-ÖMG (Austrian and German Mathematical Society) joint annual conference, University of Passau, virtual conference
- June 19 2020: Set Theory Seminar at the Fields Institute, Toronto, Canada (online seminar).
- January 2020: Visiting Philip Welch at University of Bristol.
- November 2019: RIMS Workshop, Kyoto; and visiting Jörg Brendle at Kobe University, Japan. June 5–7, 2019: Visiting University of Copenhagen.
- May 14: UniversitéParis Diderot.
- February 15, 2019: logic seminar talk at the Fields Institute, University of Toronto.
- February 5, 2019: logic seminar talk at McGill University.
- February 2019: visiting Marcin Sabok at McGill University, Canada.
- January 2019: Arctic Set Theory 4, Kilpisjärvi, Finland.
- October 5, 2018: Set Theory Seminar talk at City Universtity New York, USA.
- October 2, 2018: Logic seminar talk at McGill University, Canada.
- August 2018: KNAW Academy Colloquium Generalized Baire space, Amsterdam, The Netherlands.
- June 2018: Descriptive Set Theory Conference, Lausanne, Switzerland.
- June 2018: 11th Young Set Theory Workshop, Lausanne Switzerland.
- Februar 2018: Visiting Asger Törnquist and Karen Bakke Haga at University of Copenhagen.
- September 2017: Descriptive Set Theory in Turin, Torino, Italy.
- August 2017: Logic Colloquium, Stockholm, Sweden.
- July 2017: European Set Theory Conference, Budapest, Hungary.
- January 2017: Arctic Set Theory 3, Kilpisjärvi, Finland.
- November 2016: RIMS Workshop on Infinite Combinatorics and Forcing, Kyoto, Japan.
- August 2016: Invited talk at Logic Colloquium 2016 (special session: set theory), Leeds, UK.
- June 2016: SETTOP, Novi Sad, Serbia.
Events I have helped organize
On World Logic Day, January 14th 2022, we had a series of talks at the Toronto Set Theory Seminar at Fields Institute.
A long time ago, the famous Young Set Theory Workshop put up its tent in Copenhagen, organized by Karen Bakke Haga, Vibeke Quorning, Asger Törnquist, and me. We acknowledge generous support from the DNRF Niels Bohr Professorship of Lars Hesselholt and from the University of Copenhagen.
A few Slides from long ago
- If you are not a set theorist, maybe you will enjoy these slides; I made them with a general mathematical audience in mind, for a talk in the descriptive set theory seminar in Copenhagen on January 9th 2014.
- Here are some slides for my talk at the 4th European Set Theory Conference in Barcelona, in July 2013.