Posted August 22, 2023
Last modified August 24, 2023
Algebra and Number Theory Seminar Questions or comments?
3:10 pm – 4:00 pm Lockett 233 or click here to attend on Zoom
Xingting Wang, Louisiana State University
What are automorphism groups and where to find them?
We will discuss the automorphism problem in number theory, algebraic geometry, Poisson geometry, and quantum algebras from both classical and quantum group perspectives. The focus will be on recent progress and open conjectures in specific topics.
Posted August 22, 2023
Last modified September 4, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Dermot McCarthy, Texas Tech University
The number of $\mathbb{F}_q$-points on diagonal hypersurfaces with monomial deformation
In this talk, we consider the problem of counting the number of solutions to equations over finite fields using character sums. We start with a review of standard techniques and discuss Weil's seminal 1949 paper, which gives an exposition on the topic up to that point by examining diagonal hypersurfaces. We then consider the family of diagonal hypersurfaces with monomial deformation $$D_{d, \lambda, h}: x_1^d + x_2^d \dots + x_n^d - d \lambda \, x_1^{h_1} x_2^{h_2} \dots x_n^{h_n}=0$$ where $d = h_1+h_2 +\dots + h_n$ with $\gcd(h_1, h_2, \dots h_n)=1$, which was studied by Koblitz over $\mathbb{F}_{q}$ in the case ${d \mid {q-1}}$. We outline recent results where we provide a formula for the number of $\mathbb{F}_{q}$-points on $D_{d, \lambda, h}$ in terms of Gauss and Jacobi sums, which generalizes Koblitz's result. We then express the number of $\mathbb{F}_{q}$-points on $D_{d, \lambda, h}$ in terms of a $p$-adic hypergeometric function previously defined by the speaker. The parameters in this hypergeometric function mirror exactly those described by Koblitz when drawing an analogy between his result and classical hypergeometric functions.
Posted September 24, 2023
Last modified September 29, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Cheng Chen, University of Minnesota
Progresses on the local Gan-Gross-Prasad conjecture
The local Gan-Gross-Prasad conjecture speculates the generalization of branching problems for classical groups over local fields using classification in the Langlands problem. It has global applications related to automorphic forms and arithmetic. Works of Waldspurger, Moeglin, Beuzart-Plessis, Gan, Ichino, and Atobe completed the conjecture over non-archimedean local fields. Based on the local trace formula results in the work of Beuzart-Plessis and Luo, I will introduce an approach for the conjecture over archimedean local fields, including joint work with Luo and joint work with Chen and Zou.
Posted September 24, 2023
Last modified October 5, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Tewodros Amdeberhan, Tulane University
Generalized divisor sums and integer partitions
Our story and motivation go back to MacMahon, in which divisor sums are generalized and connections were made to partitions. We extend the argument for a variation of this development where we link our multi-variable $q$-series to alternative formulation, including multiple $q$-zeta values, quasi-modular forms. This is joint work with George Andrews and Roberto Tauraso.
Posted September 4, 2023
Last modified October 15, 2023
Algebra and Number Theory Seminar Questions or comments?
2:30 pm – 3:20 pm Lockett 233 or click here to attend on Zoom
Tong Liu, Purdue University
Prismatic crystals and $p$-adic Galois representations
$p$-adic Galois representations are an important object and a very power tool in number theory. In this talk, I will explain how to use prismatic theory, recently developed by Bhatt and Scholze, to understand $p$-adic Galois representations. In particular, I will explain how to use prismatic crystal to understand crystalline and semi-stable $p$-adic local systems.
Posted August 22, 2023
Last modified September 24, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Kalani Thalagoda, Tulane University
Bianchi Modular Forms over $\mathbb{Q}(\sqrt{-17})$
Bianchi modular form are a generalization of classical modular forms defined over imaginary quadratic fields. A theory of modular symbols exists for computing Bianchi modular forms as Hecke eigensystems. However, when the class group of the imaginary quadratic field is nontrivial, modular symbol techniques only compute the principal part of the eigensystem. In this talk, I will explain how to extract a Hecke eigensystem for $\mathbb{Q}(\sqrt{-17})$, which has a class group of order $4$.
Posted September 24, 2023
Last modified November 5, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Hui Xue, Clemson University
Coefficients of Hecke polynomials
Hecke operators play an important role in the theory of modular forms. Information about Hecke operators can be obtained through the study of their characteristic polynomials, the so-called Hecke polynomials. In this talk, I will discuss results on the nonvanishing and non-repetition properties of certain coefficients of Hecke polynomials.
Posted September 4, 2023
Last modified November 10, 2023
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Jason Gaddis, Miami University
Ozone groups of noncommutative algebras
The ozone group of a noncommutative algebra is defined as the group of algebra automorphisms which fix every element of its center. This functions like a kind of Galois group for the algebra. In this talk, I will discuss the ozone group in the context of PI Artin–Schelter regular algebras and its applications to characterizing skew polynomial rings and their centers.
Posted September 24, 2023
Last modified November 26, 2023
Algebra and Number Theory Seminar Questions or comments?
2:30 pm – 3:20 pm Lockett 233 or click here to attend on Zoom(Originally scheduled for 3:20 pm)
Hongdi Huang, Rice University
Twisting Manin's universal quantum groups and comodule algebras
Symmetry is an important concept that appears in mathematics and theoretical physics. While classical symmetries arise from group actions on polynomial rings, quantum symmetries are introduced to understand certain quantum objects (e.g., quantum groups) which appear in the theory of quantum mechanics and quantum field theory. In this talk, we will define Manin's universal quantum groups and its 2-cocycle twist. Moreover, we will talk about the invariants under the tensor equivalence of quantum symmetries.
Posted November 13, 2023
Last modified January 21, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Rena Chu, Duke University
Generalizations of the Schrödinger maximal operator: building arithmetic counterexamples
In 2016 Bourgain applied Gauss sums to construct a counterexample related to a decades-old question in PDEs. The story started in 1980 when Carleson asked about how "smooth" an initial data function must be to imply pointwise convergence for the solution of the linear Schrödinger equation. After progress by many authors, this was resolved by Bourgain, whose counterexample construction proved a necessary condition on the regularity, and Du and Zhang, who proved a sufficient condition. Bourgain's methods were number-theoretic, and this raised a natural question: could number-theoretic properties of other exponential sums have implications for other dispersive PDEs? We develop a flexible new method to construct counterexamples for analogues of Carleson's question. In particular, this applies the Weil bound for exponential sums, a consequence of the truth of the Riemann Hypothesis over finite fields.
Posted November 13, 2023
Last modified January 21, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Zhongkai Mi, Louisiana State University
The Lowest Discriminant Ideals of Cayley-Hamilton Hopf Algebras
Discriminant ideals for an algebra $A$ module finite over a central subring $C$ are indexed by positive integers. We study the lowest of them with nonempty zero set in Cayley Hamilton Hopf algebras whose identity fibers are basic algebras. Key results are obtained by considering actions of characters in the identity fiber on irreducible modules over maximal ideals of $C$ and actions of winding automorphisms. We apply these results to examples in group algebras of central extensions of abelian groups, big quantum Borel subalgebras at roots of unity and quantum coordinate rings at roots of unity. This is joint work with Quanshui Wu and Milen Yakimov.
Posted November 13, 2023
Last modified February 2, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Rajat Gupta, University of Texas at Tyler
On summation formulas attached to Hecke's functional equation and $p$-Herglotz functions
In this talk, we will review the work of Chandrasekharan and Narasimhan on the theory of Hecke’s functional equation (with one gamma factor) and the summation formulas of various kinds, such as the Voronoi summation formula, the Poisson summation formula, and the Abel-Plana summation formula. We will then give recent developments in this theory followed by some new results and summation formulas in the setting of Hecke’s functional equation analogous to the ones mentioned above. In particular, I will discuss these summation formulas in the case of cusp corms of weight $2k$ attached to the modular group ${\rm SL}_2(\mathbb{Z})$. Finally, I will also talk about on my recent work with Rahul Kumar on Herglotz functions and their analogues.
Posted February 5, 2024
Last modified February 14, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Hasan Saad, University of Virginia
Distributions of points on hypergeometric varieties
In the 1960's, Birch proved that the traces of Frobenius for elliptic curves taken at random over a large finite field is modeled by the semicircular distribution (i.e., $SU(2),$ the usual Sato-Tate for non-CM elliptic curves). In this talk, we show how the theory of harmonic Maass forms and modular forms allow us to determine the limiting distribution of normalized traces of Frobenius over families of varieties. For Legendre elliptic curves, the limiting distribution is $SU(2),$ whereas for a certain family of $K3$ surfaces, the limiting distribution is $O(3).$ Since the $O(3)$ distribution has vertical asymptotes, we show how to obtain an explicit result by bounding the error. Additionally, we show how to count "matrix" points on these varieties and therefore determine the limiting distributions for these "matrix points."
Posted November 14, 2023
Last modified February 27, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Eleanor McSpirit, University of Virginia
Infinite Families of Quantum Modular 3-Manifold Invariants
In 1999, Lawrence and Zagier established a connection between modular forms and the Witten-Reshetikhin-Turaev invariants of 3-manifolds by constructing q-series whose radial limits at roots of unity recover these invariants for particular manifolds. These q-series gave rise to some of the first examples of quantum modular forms. Using a 3-manifold invariant recently developed Akhmechet, Johnson, and Krushkal, one can obtain infinite families of quantum modular invariants which realize the series of Lawrence and Zagier as a special case. This talk is based on joint work with Louisa Liles.
Posted November 13, 2023
Last modified March 3, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Edmund Yik-Man Chiang, The Hong Kong University of Science and Technology
Discrete special functions: a D-modulus approach to special functions
We show that there is a holonomic D-modules (PDEs) approach to classical special functions, as such both the classical special functions and their difference analogues, some have only been found recently, can be efficiently computed by Weyl-algebraic framework. According to Truesdell, rudiments of algebraic approaches to special functions were already observed by some nineteenth century mathematicians. This algebraic method does not use well-known Lie algebra theory explicity apart from basic knowledge of solving linear PDEs. We illustrate our method with Bessel functions in this talk. We shall also explain the connection with this D-modules approach with recent advances in Nevanlinna theories for difference operators, which have its roots from discrete Painleve equations.
Posted November 14, 2023
Last modified March 26, 2024
Algebra and Number Theory Seminar Questions or comments?
3:20 pm – 4:10 pm Lockett 233 or click here to attend on Zoom
Micah Milinovich, University of Mississippi
Biases in the gaps between zeros of Dirichlet L-functions
We describe a family of Dirichlet L-functions that provably have unusual value distribution and experimentally have a significant and previously undetected bias in the distribution of gaps between their zeros. This has an arithmetic explanation that corresponds to the nonvanishing of a certain Gauss-type sum. We give a complete classification of the characters for when these sums are nonzero and count the number of corresponding characters. It turns out that this Gauss-type sum vanishes for 100% of primitive Dirichlet characters, so L-functions in our newly discovered family are rare (zero density set amongst primitive characters). If time allows, I will also describe some newly discovered experimental results concerning a "Chebyshev-type" bias in the gaps between the zeros of the Riemann zeta-function. This is joint work with Jonathan Bober (Bristol) and Zhenchao Ge (Waterloo).