Organizers.
Nathan Grieve: nathan.m.grieve@gmail.com (Contact organizer)
Antonio Lei: alantoniolei@gmail.com
Ben Forras bforras@uottawa.ca
Webpage of the Ottawa-Carleton Number Theory group:
Fall 2026
The intent is to start the seminar a bit later in the Fall, for instance mid-October. More details will be posted here in due course. Of course, please reach out to any of the organizers in case that you have interest in giving a talk (either in person or virtual). The default seminar times will be finalized in due course, however provisionally either Monday or Wednesday, or a combination of both, from 16:00-17:00 has been proposed. The location for each talk will change from week to week so please do be aware of that.
List of confirmed speakers:
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7 October, 2026, 4pm Ottawa time
In person lecture (with Zoom live stream)
Location: STEM-464
Masih Hamidi (McGill University)
Title: On the Comparison of the D-new Modular Degree and the Shimura Degree of Modular Abelian Varieties
Abstract: Let E be an elliptic curve over \mathbb{Q}. Under mild assumptions on the local Galois representations attached to E, we prove that the degree of the Shimura parametrization of E arising from the optimal quotient J^D(M)⟶E is equal to the D-new modular degree of E.
As applications, we establish a conjecture of Deines asserting the equality of the D-new modular degree, the D-new congruence number, and the Shimura degree of E. After introducing the Shimura congruence number into this framework, we further show that all four quantities coincide. Moreover, we prove that the two congruence numbers are always equal.
The proofs rely on new cases of multiplicity one for Shimura Jacobians, which we establish and then use to prove the main results, following a strategy introduced by Agashe, Ribet, and Stein.
The results apply more generally when E is replaced by a higher-dimensional modular abelian variety, but for simplicity I will focus on the elliptic-curve case in the talk.
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14 October, 2026, 4pm Ottawa time
In person lecture (with Zoom live stream)
Michael Chitayat (University of Padova)
Location: STEM-512
Title: Borel subgroups of automorphism groups of affine varieties
Abstract: Let X be an affine variety. It was recently proved that a connected solvable subgroup of Aut(X) can be decomposed as a semi-direct product of an algebraic torus T and a nested unipotent subgroup U. A Borel subgroup of Aut(X) is a maximal element of the set of connected solvable subgroups of Aut(X). In this talk, I will discuss Borel subgroups of Aut(X) and their associated Lie algebras.
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20 October, 2026, 4pm Ottawa time
In person lecture (with Zoom live stream)
Amrinder Kaur (Queen's University)
Location: STEM-464
Title: Sign changes in the Fourier coefficients of automorphic forms
Abstract: Understanding the behaviour of arithmetic functions has long been of interest to number theorists. One aspect of this distribution is that most arithmetic functions oscillate. Studying these oscillations often sheds light on the zeroes of the associated Dirichlet series. A higher-degree variant for this is the study of the sign changes in the Fourier coefficients of automorphic forms. In this talk, we will examine recent results concerning the sign changes in Fourier coefficients of modular forms and Maass forms. We will also see how the results vary when we consider the sign changes in the Fourier coefficients on sparse subsequences like the sum of squares.
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4 November, 2026, 10:30am Ottawa time (postponed until Winter 2027)
In person lecture (with Zoom live stream)
Juan Pablo Llerena Cordova (University of Ottawa)
Location: STEM-464
Title: TBD
Abstract: TBD
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11 November, 2026, 10:30am Ottawa time
In person lecture (with Zoom live stream)
Location: STEM-464
Dean Lin (UAmherst)
Title: TBD
Abstract: TBD
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20 November, 2026, 1:30pm Ottawa time
In person lecture (with Zoom live stream)
Location: STEM-464
Preston Wake (Michigan State University)
Title: TBD
Abstract: TBD
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26 November, 2026, 10am Ottawa time
Virtual lecture (Zoom live stream)
Justina Lückehe (Universität der Bundeswehr München)
Title: TBD
Abstract: TBD
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7 December, 2026, time TBD
Virtual lecture (Zoom live stream)
Matt Olechnowicz (University of Cambridge)
Title: TBD
Abstract: TBD
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15 December, 2026, time TBD
In person lecture (with (Zoom live stream)
Chris Middlebrook (Carleton University)
Title: TBD
Abstract: TBD
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