Shana Yunsheng Li

Ph.D. Student at
Department of Mathematics
University of Illinois Urbana-Champaign

Advisor: Nathan Dunfield

Email: yl202illinois.edu

Pronoun: She/Her


My Blåhaj
Introduction & CV Research Teaching Outreach

Research

Publications

Title Year
Patterns of the \(V_2\)-polynomial of knots 2024
Abstract (click to expand)

Recently, Kashaev and the first author defined a sequence \(V_n\) of \(2\)-variable knot polynomials with integer coefficients, coming from the \(R\)-matrix of a rank \(2\) Nichols algebra, the first polynomial been identified with the Links-Gould polynomial. In this note we present the results of the computation of the \(V_n\) polynomials for \(n=1,2,3,4\) and discover applications and emerging patterns, including unexpected Conway mutations that seem undetected by the \(V_n\)-polynomials as well as by Heegaard Floer Homology and Knot Floer Homology.

Joint work with Stavros Garoufalidis. arXiv:2409.03557.
Related Talk: Patterns or conspiracy theories of knots by Stavros Garoufalidis at Conference on Recent Developments in Topological Quantum Field Theory, BIMSA.
Algebraic aspects of holomorphic quantum modular forms 2024
Abstract (click to expand)

Matrix-valued holomorphic quantum modular forms are intricate objects that arise in successive refinements of the Volume Conjecture of knots and involve three holomorphic, asymptotic and arithmetic objects. It is expected that the algebraic properties of these objects can be deduced from the algebraic properties of descendant state integrals, and we illustrate this for the case of the \((-2,3,7)\)-pretzel knot.

Joint work with Ni An and Stavros Garoufalidis. Research in Mathematical Sciences 11 (2024) no.3, Paper No. 54, 1-20. arXiv:2403.02880.

Projects

Title Year
\(V_2\)-polynomials of slalom knots Ongoing
Joint work with Stavros Garoufalidis and Norbert A'Campo.
Census of \(10\) tetrahedra oriented cusped hyperbolic manifolds Ongoing
Joint work with Nathan Dunfield. Github repository: snappy_10_tets.

Talks

Title Location Time
Multivariable knot polynomials, the \(V_n\)-polynomials, and their patterns. Slides.
Abstract (click to expand)

Quantum knot invariants are known to come from $R$-matrices along with some extra structures, a process called the Reshetikhin--Turaev functor. In $2019$, Rinat Kashaev proved that $R$-matrices alone are sufficient to define knot invariants, as long as they satisfy some nondegeneracy conditions called rigidity. More recently, Stavros Garoufalidis and Rinat Kashaev developed a new method of constructing rigid $R$-matrices, which recovers several known knot polynomials such as the colored Jones polynomials, and gives a new family of multivariable knot polynomials, the $V_n$-polynomials. In this talk, I will talk about the Reshetikhin--Turaev functor in this context, the computation of $V_n$-polynomials and the patterns of the results based on $361404$ knots computed. Joint work with Stavros Garoufalidis.

Seminar talk at the Group, Geometry and Topology Seminar (UIUC) Aug. 2025
Invited online talk at the Shanghai Institute for Mathematics and Interdisciplinary Sciences (SIMIS) Apr. 2025
Seminar talk at the Graduate Geometry-Topology Seminar (UIUC). Mar. 2025
The Teichmüller TQFT and the quantum modularity conjecture. Seminar talk at the Graduate Topology Seminar (SUSTech). Mar. 2024

Theses

Title Degree
On the Quantum Modularity Conjecture for Knots M.Sc
Abstract (click to expand)

Quantum topology is considered to be initiated by the discovery of the Jones polynomial in 1984, followed with observations of numerous links to physics. In the late '80s, Atiyah, Segal, and Witten established an intrinsic definition of the Jones polynomial using \(\text{SU}(2)\) Chern-Simons theory, revealing the rich connections of the Jones polynomial with the physical world. Successive findings around the Jones polynomial emerged, including one famous conjecture that is the main topic of this thesis, the Quantum Modularity Conjecture.

In 1995, R. Kashaev introduced a knot invariant using the quantum dilogarithm function, which for a hyperbolic knot K is conjectured to have an exponential growth rate, a conjecture known as the Volume Conjecture. In 2001, H. Murakami and J. Murakami discovered that Kashaev's invariant is equal to the value of the \(N\)-colored Jones polynomial at \(N\)-th roots of the unity. With this, D. Zagier observed a modular relation between the values of the \(N\)-colored Jones polynomial at different roots of the unity and extended the statement of Volume Conjecture to a modular relation of the functions. The extended statement is known as the Quantum Modularity Conjecture (QMC).

More recently, J. E. Andersen and R. Kashaev introduced the Teichmuller TQFT based on Chern-Simons theory with infinite dimensional gauge groups, promoting the quantum Teichmuller theory to a TQFT of categroids. On further investigation into values of the Teichmuller TQFT on knot complements of the \(4_1\) knot and the \(5_2\) knot, S. Garoufalidis and D. Zagier discovered phenomena suggesting deep relationships between the state integral from the Teichmuller TQFT and QMC. Furthermore, their observation also suggested rich connections with several other topics, such as the Dimofte-Gaiotto-Gukov index and the quantum spin network.

This thesis will mainly focus on introducing the construction of the Teichmuller TQFT and the contents of QMC, and demonstrate their connections by listing the observations made by S. Garoufalidis and D. Zagier and more recent results along with elementary proofs for some of them from joint work of the author, N. An and S. Garoufalidis.

Foundation of Supergeometry and Its Application in Mathematical Physics B.Sc
Abstract (click to expand)

Supergeometry is a natural extension of the theory of differential geometry, which enjoys values on its own right as a purely mathematical object, and also turns out to be useful in physics: it gives a model of spacetime that unifies quantum science and gravity, the string theory. The first part of this thesis gives a detailed and mathematically strict introduction to supergeometry, rearranged from the lecture notes by Covolo and Poncin, the paper of Leites and the notes by Deligne and Morgan. The second part focuses on an explicit discussion on the important example \(\underline{\text{SMan}}(R^{0|\delta},X)\) and outlines a corresponding proof of the Chern-Gauss-Bonnet theorem, following Berwick-Evans’ work.


Notes

Title Year
Notes of Zelmanov's Algebraic Lectures 2023
Taken by me based on the contents of the lectures given by Prof. Efim Zelmanov in 2023 Spring at SUSTech. The topics include Gröebner-Shirshov bases theorem, Wreath product, Burnside's problems, rings of fractions and ultraproducts.
A Review From Manifolds to Basic de Rham Theory 2021
A quick and compact review of basic notions of smooth manifolds and a beginning of de Rham theory. Served as a preliminary material in the reading seminar of Bott & Tu's Differential Forms in Algebraic Topology.