Department of Mathematics and Statistics

Department of Mathematics and Statistics
Department of Mathematics and Statistics
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Calabi-Yau Manifolds & Mirror Symmetry Seminar

CYMS Seminar - Oswaldo Sevilla

Thursday, November 14th, 2019

Time: 2:30 p.m Place: Jeffery Hall 319

Speaker: Oswaldo Sevilla (Fields Institute and Centro de Investigacion en Matematicas A.C.)

Title: Calabi Yau Threefolds arising from certain root lattices.

Abstract: I'll show my work on the construction of Calabi Yau threefolds that are constructed from the C_3 and C_4 root systems, using a construction by H. Verrill (Root lattices and pencils o f varieties, 1996) based on a paper of V. Batyrev (Dual Polyhedra and mirror symmetry for Calabi-Yau hypersurfaces in toric varieties,1994).

CYMS Seminar - Fenglong You (University of Alberta)

Thursday, October 17th, 2019

Time: 2:30 p.m Place: Jeffery Hall 319

Speaker: Fenglong You (University of Alberta)

Title: Relative Gromov--Witten theory and mirror symmetry

Abstract: Gromov--Witten theory is considered as the first modern approach in enumerative geometry. Absolute Gromov--Witten invariants provide virtual counts of curves in smooth projective varieties/orbifolds. It is known to have many nice structural properties, such as quantum cohomology, WDVV equation, Givental's formalism, mirror theorem, CohFT etc.. Relative Gromov--Witten invariants study the virtual counts of curves in varieties with tangency conditions along a divisor. In this talk, I will give an overview of some recent developments on parallel structures of relative Gromov--Witten theory. If time permits, I will also talk about some applications such as SYZ mirror symmetry and Doran--Harder--Thompson conjecture.

CYMS Seminar - Richard Gottesman (Queen's University)

Thursday, September 5th, 2019

Time: 2:30 p.m Place: Jeffery Hall 319

Speaker: Richard Gottesman (Queen's University)

Title: Vector-Valued Modular Forms and Modular Linear Differential Equations

Abstract: The sequence of denominators of the Fourier coefficients of a modular form on a congruence subgroup is always bounded. It has been conjectured that the converse is also true. We will consider this problem in the context of vector-valued modular forms and explain a strategy for proving such an unbounded denominator result. A key point is the importance of understanding the solutions of the modular linear differential equation at all of the cusps).

CYMS Seminar - Noriko Yui (Queen's University)

Thursday, October 18th, 2018

Time: 11:30 a.m - 12:20 p.m Place: Jeffery Hall 422

Speaker: Noriko Yui (Queen's University)

Title: Four-dimensional Galois representations arising from certain Calabi--Yau threefolds Part II

Abstract: We consider the (irreducible) four-dimensional Galois representations arising from certain Calabi--Yau threefolds over ${\bf{Q}}$ with all the Hodge numbers of the third cohomology groups equal to $1$. There are many examples of (families) of such Calabi--Yau threefolds. The modularity/automorphy of such Calabi--Yau threefolds will be the main topic of discussion. There are two venues to be considered. In one venue, we ought to count the number of rational points over finite fields of these Calabi--Yau threefolds to concoct their L-series. In the other venue, we ought to construct some modular varieties, in this case, conjecturally, Siegel modular forms of weight $3$ and genus $2$ on some paramodular subgroups of $Sp(4,{\bf{Z}})$, and then compute their L-series. Such modular forms may be constructed using Borcherds forms. The ultimate aim is to establish a Langlands correspondence between the two L-series, thereby establishing the modularity/automorphy of such Calabi--Yau threefolds.

This is a joint work with Yifan Yang (National Taiwan University).

CYMS Seminar - Noriko Yui (Queen's University)

Thursday, September 27th, 2018

Time: 11:30 a.m - 12:20 p.m Place: Jeffery Hall 422

Speaker: Noriko Yui (Queen's University)

Title: Four-dimensional Galois representations arising from certain Calabi--Yau threefolds

Abstract: We consider the (irreducible) four-dimensional Galois representations arising from certain Calabi--Yau threefolds over ${\bf{Q}}$ with all the Hodge numbers of the third cohomology groups equal to $1$. There are many examples of (families) of such Calabi--Yau threefolds. The modularity/automorphy of such Calabi--Yau threefolds will be the main topic of discussion. There are two venues to be considered. In one venue, we ought to count the number of rational points over finite fields of these Calabi--Yau threefolds to concoct their L-series. In the other venue, we ought to construct some modular varieties, in this case, conjecturally, Siegel modular forms of weight $3$ and genus $2$ on some paramodular subgroups of $Sp(4,{\bf{Z}})$, and then compute their L-series. Such modular forms may be constructed using Borcherds forms. The ultimate aim is to establish a Langlands correspondence between the two L-series, thereby establishing the modularity/automorphy of such Calabi--Yau threefolds.

This is a joint work with Yifan Yang (National Taiwan University).

CYMS Seminar - Richard Gottesman (Queen's University)

Thursday, September 20th, 2018

Time: 11:30 a.m - 12:20 p.m Place: Jeffery Hall 422

Speaker: Richard Gottesman (Queen's University)

Title: Vector-Valued Modular Forms on $\Gamma_{0}(2)$C

Abstract: The collection of vector-valued modular forms form a graded module over the graded ring of modular forms. I will explain how understanding the structure of this module allows one to show that the component functions of vector-valued modular forms satisfy an ordinary differential equation whose coefficients are modular forms. In certain cases, we can use a Hauptmodul to transform such a differential equation into a Fuchsian differential equation on the projective line minus three points. We then are able to use the Gaussian hypergeometric series to explicitly solve this differential equation.
Finally, we make use of these ideas together with some algebraic number theory to study the prime numbers that divide the denominators of the Fourier coefficients of the component functions of vector-valued modular forms.

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