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Jesse Huang, University of Waterloo

Organizational Meeting

This is an organizational meeting for the mirror symmetry learning seminar. We will skim through the reading list and topics to cover and assign talks. All are welcome!

MC 2017

Amanda Maria Petcu, University of Waterloo

Cohomogeneity one solitons of the hypersymplectic flow

Given a manifold X^4 x T^3 where X^4 is hypersymplectic, one can give a flow of hypersymplectic structures that evolve according to the equation dt(w) = d(Q d^*(Q^{-1} w)), where w is the triple that gives the hypersymplectic structure and Q is a 3x3 symmetric matrix that relates the symplectic forms w_i to one another. We will let X^4 be R^4 with a cohomogeneity one action and explain what it means to be a soliton for the hypersymplectic flow and examine a (potentially hyperkahler) metric that comes from this set-up.

MC 5479

Owen Sharpe, University of Waterloo

The Selberg-Delange Method

For complex w and z, the expression w^z is ambiguous, requiring a choice of branch of log(w). In particular, there is no way to make w^z an entire function of w; a branch cut will always be present. In turn, this makes it difficult to perform contour integration and calculate residues with functions of the form f(w)^z, which are fundamental operations in number theory. We describe Selberg's method for performing such computations and some of its applications, such as those by Selberg and Delange. Incidentally, we will also discuss Hankel's formula for the Gamma function and Perron's formula for partial sums of Dirichlet series.

MC 5403

Luis Fernandez (City University of New York)

The Dirac operator in the Clifford bundle and Kaehler identities for almost complex manifolds

We use the Dirac operator in the Clifford bundle of an almost complex manifold to obtain a different formulation of the Kaehler identities which, when viewed in the exterior bundle, give the known generalization of these identities for complex manifolds found by Demailly, thus obtaining a generalization of the Kaeher identities for almost complex manifolds. This result was also proved by de la Ossa, Karigiannis, and Svanes.

In the process we will define a number of operators in the Clifford bundle, together with relations between them, that should give an alternative way to study almost complex manifolds.

All the work presented is joint with Sam Hosmer.

MC 5417

Catherine St-Pierre, University of Waterloo

Sheppard-Todd-Chevalley theorem (and beyond)

Sheppard-Todd-Chevalley's theorem is one of the most significant results in invariant theory. It provides necessary and sufficient conditions for the fixed subring k[x_1, \dots , x_n]^G under a finite subgroup G of GL_n(k) to be a polynomial ring. We will review the theorem and its applications and summarise some generalisations.

MC 5479

Rahim Moosa, University of Waterloo

Curve excluding fields II

Recently, Johnson and Ye have proved an attractive and somewhat surprising result: Suppose C is an algebraic curve of genus at least two having no rational points. Then the class of fields over which C has no rational points, has a model companion. This model companion, they call it CXF, turns out to answer several old questions.

I will start presenting the results of the paper.

MC 5403

Leigh Foster, University of Waterloo

Introduction to planar tilings

From tangrams to tessellations to brick pavers, we have many real life examples of tilings of a planar region. In this learning seminar, we will get a gentle introduction to the math behind these ideas, and over the course of the term will be able to answer the questions: Given a set of tiles, can we determine if a given region is tilable? If so, do we have more than one way of laying out the tiles? How can we know when a tiling does not exist? To answer these questions, we'll use techniques including counting and coloring arguments, height functions from a more topological point of view, and a combinatorial group-theoretic approach, among others. No previous knowledge is needed, and no outside work is required! Come and listen and ask questions - everyone is welcome, and interruptions are expected.

For our first meeting, we will discuss the basics of tilings. What does it mean to tile a region, and what are some ways that these questions arise in mathematics?

MC 5403

Daniel Gromada, Czech Technical University

Quantum association schemes

This talk is based on a preprint arXiv:2404.06157. We start by briefly explaining what a quantum group is and how quantum graphs are defined. Then, we recall what association schemes are and we apply the quantization procedure here. As a result, this allows to define distance regular and strongly regular quantum graphs. In addition, we observe that the duality for translation association schemes extends to the quantum setting.

MC 5417 or Join on Zoom

Faisal Romshoo, University of Waterloo

Topological calibrations and their moduli spaces

We discuss an approach to deformation problems of geometric structures laid out in https://arxiv.org/abs/math/0112197 by Ryushi Goto. In particular, we will explore the cohomological conditions under which the moduli space of the geometric structures become smooth manifolds of finite dimension. As an application, we will prove the unobstructedness of G2 structures and if time permits, of Spin(7)-structures as well.

MC 5479

Krishnarjun Krishnamoorthy, BIMSA

Moments of non-normal number fields

Let K be a number field and a_K(m) be the number of integral ideals in K of norm equal to m. We asymptotically evaluate the sum \sum_{m\leqslant X} a_K^l(m) as X grows to infinity. We also consider the continuous moments of the associated Dedekind zeta function and prove lower bounds of the expected order of magnitude.

Join on Zoom