University of Denver
An article on being a mathematician
Annals of Pure and Applied Logic.
In January 2020, I became an editor for the Annals of Pure and Applied Logic, handling papers in set theory and related areas.
Advising and Postdoctoral Mentoring.
Timothy Trujillo PhD in Spring 2014 with thesis: "Topological Ramsey spaces, associated ultrafilters, and their applications to the Tukey theory of ultrafilters and Dedekind cuts of nonstandard arithmetic".
Sonia Navarro Flores (co-advised with Michael Hrusak) PhD in January 2021 with thesis: "Topological Ramsey spaces and Borel ideals".Postdoctoral Mentoring.
Jose Mijares DU Postdoctoral Visiting Assistant Professor: Fall 2013 - Spring 2015.
Daniel Hathaway DU Postdoctoral Visiting Assistant Professor: Fall 2015 - Spring 2018.
Dr. Kaiyun Wang, College of Mathematics and Information Science, Shaanxi Normal University was a DU visiting research scholar from November 2018 - November 2019.Masters Thesis Advising.
Sonia Navarro Flores (co-advised with David Meza-Alcantara) in 2015 on her Masters Thesis: "Ramsey numbers for ultrafilters associated to topological Ramsey spaces."
As of January 1, 2021, my term as Chair of the ASL Committee on Logic in North America has been completed. The new Chair is Thomas Scanlon. My past service includes 6-years as a member of the Committee on Logic in North America, and a two-year term on the ASL Web Advisory Committee.
Research. I work in Set Theory, Ramsey Theory, Topology, and related areas. See my Research Page for more information.
Ramsey Theory on Infinite Structures. One of my current research interests is mapping out those infinite structures which have analogues of the infinite Ramsey theorem. This is the area of "big Ramsey degrees" and "infinite dimensional Ramsey theory." This area has its beginnings in Sierpinski's example of a coloring of (unordered) pairs of rationals into two colors so that any subset forming a dense linear order without endpoints (that is, isomorphic as a linear order to the rationals) still has pairs with both colors. An expository article on Ramsey theory on infinite structures and the method of strong coding trees, which I developed to prove that the triangle-free Henson graph has finite big Ramsey degrees and extended to prove that all Henson graphs have finite big Ramsey degrees, will appear this fall in "Contemporary Logic and Computing," the first of a several volume international project on Current Trends in Logic.
In the summer of 2020, I finished a proof characterizing the exact big Ramsey degrees of the triangle-free Henson graph. This was proved via a small tweak in the triangle-free coding trees developed here. The same result was around the same time independently obtained by Balko, Chodounsky, Hubicka, Konecny, Vena, and Zucker using different methods. Together, we are writing a joint paper finding exact big Ramsey degrees of all free amalgamation classes of structures with finitely many binary (and unary) relations with irreducible forbidden substructures, building on Zucker's work for the upper bounds as well as new combinatorial methods for upper bounds developed by Hubicka using parameter spaces.Recently, with Coulson and Patel, we have formulated a property (SDAP^+) strengthening the Disjoint Amalgamation Property, and proved that any Fraisse class with SDAP^+ admits a big Ramsey structure, which moreover is simply characterized by two additional relations. (See Zucker's Big Ramsey degrees and topological dynamics for the definition of "big Ramsey structure".) This work characterizes exact big Ramsey degrees for a large collection of new Fraisse classes, while streamlining several previous results. Key features of the work include development of coding trees of 1-types to prove Ramsey theorems directly on the structures, and the first "envelope-free" proofs. Extending the infinite dimensional Ramsey theory of the natural numbers (Galvin-Prikry and Ellentuck Theorems) to infinite structures is in its nascent stages. A paper to appear in the proceedings of the 2016 Czech DocCourse on Ramsey Theory proved an analogue of the Galvin-Prikry theorem for the Rado graph in Borel sets of Rado graphs and Ramsey's Theorem. Working with Kaiuyn Wang, we have extended results of Huber-Geschke-Kojman and of Zhang on big Ramsey degrees of the profinite graph to more general binary relational structures. We characterize the exact big Ramsey degrees for ordered graphs, ordered k-clique-free graphs, ordered oriented graphs, and ordered tournaments inside their inverse limits. Inverse limit structures
Work Published in 2020.
"Continuous and other finitely generated canonical cofinal maps on ultrafilters," Fundamenta Mathematicae. 249 (2020), no. 2, 111--147.
(With Dan Hathaway) "Forcing and the Halpern-Lauchli theorem," Journal of Symbolic Logic. 85 (2020), no. 1, 87--102.
(With Dan Hathaway and Karel Prikry) "Perfect tree forcings for singular cardinals," Annals of Pure and Logic. 171 (2020), no. 9, 102827, 25 pp.
"The Ramsey theory of the universal homogeneous triangle-free graph," Journal of Mathematical Logic. 20 (2020), no. 2, 2050012, 75 pp.
"Topological Ramsey Spaces Dense in Forcings," in the book, "Structure and Randomness in Computability and Set Theory," pp. 3-58. World Scientific, Editors: Douglas Cenzer and Jindrich Zapletal. 2020. Available online.
(With Dan Hathaway) "Barren extensions," accepted to the Journal of Symbolic Logic, is available online.
"Ramsey theory on infinite structures and the method of strong coding trees," in "Contemporary Logic and Computing," pp 444-467. College Publications, Editor: Adrian Rezus. 2020. Table of Contents
Invited Talks, Workshops, Tutorials, and Panels. For slides from 2015-2018, see Invited Talks Page.
Oberwolfach Workshop on Set Theory, January 9 - 15, 2022.
Models and Sets Seminar, University of Leeds, May 5, 2021.
Caltech Logic Seminar, March 29, 2021 (online). "Fraisse classes with simply characterized big Ramsey degrees"
Midwest Model Theory Seminar, March 9, 2021 (online). "Fraisse classes with simply characterized big Ramsey degrees"
SEALS 2021, University of Florida, Gainesville, February 27 - 28, 2021 (online). "Ramsey theory on infinite structures" (plenary).
UltraMath 2020, Pisa, Italy, May 31 - June 6, 2020. Cancelled due to Covid-19.
Online Logic Seminar. April 9, 2020. "Ramsey properties on infinite structures".
Oberwolfach Workshop on Set Theory, Oberwolfach, Germany, April 5-11, 2020. Cancelled due to Covid-19.
ASL North American Meeting, UC Irvine, March 25-28, 2020, Special Session on Forcing and Ramsey Theory. Cancelled due to Covid-19, but they held a Virtual Meeting instead. Ramsey Theory on Fraisse structures
Mathematics Department Colloquium, Boise State University, March 10, 2020. "Ramsey Theory for Infinite Structures and Set Theoretic Methods."
UCLA Logic Colloquium. February 7, 2020. Talk on Strong coding trees and Ramsey theory on infinite structures.
I gave invited talks at the JMM in the two AMS-ASL Special Sessions: "Choiceless Set Theory and Related Areas", and "Logic Facing Outward". Denver, January 15-16, 2020. Slides: Barren extensions slides and Logic and Combinatorics
Set Theory Seminar at The Hebrew University. Chalk talks on December 11 and 18, 2019 on my work on big Ramsey degrees of Henson graphs.
Set Theory Seminar, Bar-Ilan University, December 9, 2019. Chalk talk on "Strong coding trees and applications to Ramsey theory on infinite graphs."
Carlos di Prisco Birthday Meeting, Bogota, Colombia, November 28-29, 2019. Barren extensions
Fall Southeast AMS Sectional Meeting, Special Session on Cech-Stone compactification of semigroups: Algebra, Topology, Dynamics, and Combinatorics, University of Florida at Gainesville, November 2-3, 2019. I gave a chalk talk on "Ramsey ultrafilter and friends", comparing results about Ramsey ultrafilters in regard to Rudin-Keisler, Tukey, barren extensions, etc. to similar results for ultrafilters with finite Ramsey degrees.
National Academies of Sciences, Engineering, and Medicine. "Mathematical Frontiers" Webinar Series. With Julia Knight, we were panelists on the topic of Logic and Foundations, September 10, 2019.
15th International Luminy Workshop in Set Theory, Luminy, France, September 23-27, 2019. Borel sets of Rado graphs are Ramsey
Casa Matematica Oaxaca, Workshop on Reverse Mathematics of Combinatorial Principles, September 15-20, 2019. Chalk talk on "Open problems in the reverse mathematics of Ramsey theory on trees and graphs."
AMS Fall Central Sectional Meeting, Special Session on "Topology and Descriptive Set Theory," Madison, WI, September 14-15, 2019. Borel partitions of a space of Rado graphs are Ramsey
Universidad de los Andes, research visit to Carlos DiPrisco. I gave a chalk talk in the set theory seminar titled, "Tukey theory of ultrafilters."
Casa Matematica Oaxaca, Set theory of the reals, August 4-9, 2019. (unfortunately unable to attend, due to a prior commitment)
Midsummer Combinatorial Workshop XXIV, July 29 - August 2, 2019, Prague, Czech Republic. Ramsey theory on infinite graphs
Logic Fest in the Windy City, May 30 - June 2, 2019. Tutorial: Ramsey theory on trees and applications to infinite graphs
50 Years of Set Theory in Toronto, May 13-17, 2019. Strong coding trees and applications to Ramsey theory on infinite graphs
Spring Topology and Dynamical Systems Conference, March 14-16, 2019. Special Session on Set Theoretic Topology, "Borel colorings of the Rado graph". (unable to attend because of flights cancelled due to a blizzard in Denver)
Notre Dame Logic Seminar, March 5, 2019.
Miami University, February 25 - March 1, 2019. Colloquium talk.
University of Florida, February 18-23, 2019. A talk in the Colloquium, and a talk in the Logic Seminar.
Arctic Set Theory Workshop 4, Kilpisjaervi, Finland, January 21-26, 2019. Ramsey theory of the Henson graphs.
ASL Winter Meeting, at the Joint Mathematics Meetings, Baltimore, January 18-19, 2019, (plenary). Ramsey theory of the Henson graphs.
University of Oxford, Analytic Topology in Mathematics and Computer Science Seminar, January 16, 2019. Ramsey theory and infinite graphs.
University of Vienna, at the invitation of Vera Fischer, January 7-12, 2019. I gave a Mini-course on Infinitary Ramsey Theory (slides and video available here), and a lecture on the Ramsey theory of Henson graphs.
Other conferences I participated in during 2019.
British Combinatorial Conference, July 29 - August 2, 2019, Birmingham, UK. Contributed talk on "Ramsey theory on infinite graphs". This will be an overview of several papers. slides
European Set Theory Conference, July 1-5, 2019, Vienna, Austria. Contributed talk on "Barren extensions." This is joint work with Dan Hathaway extending results of Henle, Mathias, and Woodin to a large collection of sigma-closed forcings adding new ultrafilters with weak partition properties. slides
ASL Annual North American Meeting, May 20-23, 2019, CUNY, New York. Contributed talk on "Borel colorings of a space of Rado graphs". This work extends the Galvin-Prikry theorem for Borel partitions of the Baire space to Borel partitions of a topological space where each point represents a Rado graph. slides
Grants and Awards.
I am grateful to have received a third National Science Foundation Grant DMS-1901753, this one on "Logic, Ramsey Theory, and Relational Structures," which started September 1, 2019. $158,476.
In 2016, I was awarded the Excellence in Research Award, University of Denver, Division of Natural Sciences and Mathematics, for the academic year 2015-2016.See Grants and Awards for the listing of these and previous grants and awards.
I am now on sabbatical until the end of March 2021, at which point I will teach Set Theory (MATH 3050).
In Fall 2019, I am teaching Calculus (MATH 1951). In Winter 2020, I taught Mathematical Logic (MATH 3060) and Perspectives in Art (MATH 1150). In Spring 2020, I am teaching Real Analysis I (MATH 3161), online of course. In Fall 2018 I taught Calculus 1 (MATH 1951) and Set Theory (MATH 3050). In Winter 2019 I focused solely on research. In Spring 2019 I taught a graduate course in Set Theory and Infinite Combinatorics (MATH 4700). This was a new course, focusing on Ramsey Theory and forcing, drawing from Todorcevic's book "Introduction to Ramsey Spaces," Kunen's "Set Theory," and various research articles. The intent is to develop background in this area and introduce students to current research topics. I also taught Perspectives in Art (MATH 1150).
Women in Mathematics.
The Mathematics Department at DU now has an AWM Student Chapter. The Faculty Sponsor is Professor Mei Yin and I am the Faculty Co-Sponsor. I also run quarterly mentoring meetings for the women graduate students in math.
Lynn Yengulalp and I were the Program Committe for the Special Session in Set-theoretic Topology at the 54th Spring Topology and Dynamical Systems Conference, Murray State University, March 18-21, 2020. This meeting was postponed due to Covid-19 and will take place online during May 12--16, 2021.
I chaired the Program Committee for the ASL Winter Meeting at the Joint Mathematics Meeting, Denver, January 15-18, 2020.
I am on the Program Committee for the BEST conference series, 2018-2023.
Nick Galatos and I (Chair) organized BLAST 2018. This 10-year anniversary conference was held at the University of Denver, August 6-10, 2018.
Dan Hathaway and I organized a special session on Set Theory of the Reals (including Ramsey Theory) at the AMS Western Sectional Meeting at the Unviersity of Denver in October 2016.
The DU Sesquicentennial Ramsey Theory Conference 2014 was held at the University of Denver, May 24 - 28, 2014. The meeting was organized by Jose Mijares and myself. We thank the National Science Foundation and The DU Provost Sesquicentennial Fund for funding to support many participants.
DU is the birthplace of the BLAST Conference Series, which started in 2008 when Professor Nikolaos Galatos and myself co-founded and co-chaired BLAST 08. BLAST is an interdisciplinary conference focused on Boolean algebras, Logic, Lattices, algebraic Logic, universal Algebra, Set theory, and Topology (Set-theoretic, point free, and general). These are logic-related areas of interest to researchers at Chapman University; New Mexico State University, Las Cruces; University of Colorado, Boulder; University of Denver; University of Kansas, Lawrence; University of Missouri, Kansas City; University of Nebraska, Omaha; and University of North Texas. BLAST conferences are good for graduate students, early career mathematicians, and anyone interested in expanding their research to include neighboring areas. We are grateful for National Science Foundation funding for the BLAST Conference Series.
Front Range Logic Saturdays (formerly known as the Maximally Informal Gathering or MIG) is a consortium of logicians from the Boulder, Denver, Golden and Fort Collins areas. We gather on selected Saturdays to share research talks, ideas, and lunch. MIG was started in 2009 by Bart Kastermans and myself. FRLS was run by Dan Hathaway and Timothy Trujillo from 2015-2018.
I have also organized various special sessions and served on program committees for conferences of the ASL and the AMS. These are listed in my CV.
From 2008 until May 2014, I was the coordinator and supervisor for the Graduate Colloquium which meets on Fridays at 2pm. See Graduate Colloquium for a list of past and present speakers.