Shubham Sinha

Shubham Sinha's face

I am a postdoctoral fellow at the University of British Columbia in Vancouver, mentored by Prof. Jim Bryan. Previously, I was a postdoctoral fellow at the International Centre for Theoretical Physics in Trieste, where I worked with Prof. Alina Marian. I received my Ph.D. from the Department of Mathematics at the University of California San Diego in June 2023, advised by Prof. Dragos Oprea.

Here is my CV.

Research Area: Algebraic Geometry; Enumerative Geometry; Moduli Theory; Algebraic Combinatorics.

Email: myfirstname at math.ubc.ca
Office: Mathx

Shubham Sinha's face

Preprints

  • Intersection theory of Hyperquot schemes on curves
    with Riccardo Ontani and Weihong Xu
    Abstract

    We study the virtual intersection theory of Hyperquot schemes parameterizing sequences of quotient sheaves of a vector bundle on a smooth projective curve. Our results generalize the Vafa--Intriligator formula for Quot schemes and provide a closed formula for virtual counts of maps from the curve to a partial flag variety.

  • A Borel--Weil--Bott theorem for Quot schemes on ℙ^1
    with Ajay Gautam and Feiyang Lin
    Abstract

    We study the cohomology groups of tautological bundles on Quot schemes over the projective line, which parametrize quotients of a vector bundle V on ℙ^1 of arbitrary rank r. Our main result is an analogue of the Borel–Weil–Bott theorem for Quot schemes. As a corollary, we prove recent conjectures of Marian, Oprea, and Sam on the exterior and symmetric powers of tautological bundles.

Papers

  • A short way of counting maps to hypersurfaces in Grassmannians
    with Alina Marian
    Ann. Sc. Norm. Super. Pisa Cl. Sci. (to appear) | arXiv:2506.10593
    Abstract

    Using a Quot scheme compactification, we calculate the virtual count of maps of degree d from a smooth projective curve of genus g to a hypersurface in a Grassmannian, sending specified points of the curve to special Schubert subvarieties restricted to the hypersurface. We study the question of whether this virtual count is in fact enumerative under suitable conditions on the hypersurface, in the regime when the map degree d is large.

  • Quantum K-Invariants via Quot schemes II
    with Ming Zhang
    J. London Math. Soc. 114 (2026) | arXiv:2410.23486
    Abstract

    We derive a K-theoretic analogue of the Vafa--Intriligator formula, computing the (virtual) Euler characteristics of vector bundles over the Quot scheme that compactifies the space of degree d morphisms from a fixed projective curve to the Grassmannian Gr(r,N). As an application, we deduce interesting vanishing results, used in Part I to study the quantum K-ring of Gr(r,N). In the genus-zero case, we prove a simplified formula involving Schur functions, consistent with the Borel–Weil–Bott theorem in the degree-zero setting. These new formulas offer a novel approach for computing the structure constants of quantum K-products.

  • Quantum K-Invariants via Quot schemes I
    with Ming Zhang
    J. Math. Pures Appl. 213 (2026) | arXiv:2406.12191
    Abstract

    We study the virtual Euler characteristics of sheaves over Quot schemes of curves, establishing that these invariants fit into a topological quantum field theory (TQFT) valued in Z[[q]]. Utilizing Quot scheme compactifications alongside the TQFT framework, we derive presentations of the small quantum K-ring of the Grassmannian. Our approach offers a new method for finding explicit formulas for quantum K-invariants.

  • Cores of partitions in rectangles.
    with Arvind Ayyer
    Electron. J. Combin. 31(1) (2024) | arXiv:2211.07996
    Abstract

    For a positive integer t ≥ 2, the t-core of a partition plays an important role in modular representation theory and combinatorics. We initiate the study of t-cores of partitions contained in an r×s rectangle. Our main results are as follows. We first give a simple formula for the number of partitions in the rectangle that are themselves t-cores and compute its asymptotics for large r and s. We then prove that the number of partitions inside the rectangle whose t-cores are a fixed partition ρ is given by a product of binomial coefficients. Finally, we use this formula to compute the distribution of the t-core of a uniformly random partition inside the rectangle, extending our previous work on all partitions of a fixed integer n (Ann. Appl. Prob. 2023). In particular, we show that in the limit as r, s → ∞ while maintaining a fixed aspect ratio, we again obtain a Gamma distribution with shape parameter α = (t − 1)/2 and a rate parameter β depending on the aspect ratio.

  • Bergman-Einstein metrics on two-dimensional Stein spaces.
    with Soumya Ganguly
    Michigan Math. J. 76 (1) 2026. | arXiv:2210.12323
    Abstract

    We show that the Bergman metric of the ball quotients B₂/Γ, where Γ is a finite and fixed-point-free group, is Kähler–Einstein if and only if Γ is trivial. As a consequence, we characterize the unit ball B₂ among two-dimensional Stein spaces with isolated normal singularities, proving an algebraic version of Cheng's conjecture for two-dimensional Stein spaces.

  • Euler characteristics of tautological bundles over Quot schemes of curves.
    with Dragos Oprea
    Adv. Math. 418 (2023) | arXiv:2207.01675
    Abstract

    We compute the Euler characteristics of tautological vector bundles and their exterior powers over the Quot schemes of curves. We give closed-form expressions over punctual Quot schemes in all genera. For higher rank quotients of a trivial vector bundle, we obtain answers in genus zero. We also study the Euler characteristics of the symmetric powers of the tautological bundles, for rank zero quotients.

  • The virtual intersection theory of isotropic Quot Schemes.
    J. Geom. Phys. 198 (2024) | arXiv:2106.11356
    Abstract

    Isotropic Quot schemes parameterize rank r isotropic subsheaves of a vector bundle equipped with a symplectic or symmetric quadratic form. We define a virtual fundamental class for isotropic Quot schemes over smooth projective curves. Using torus localization, we prescribe a method to calculate top intersection numbers of tautological classes and obtain explicit formulas when r = 2. These include and generalize the Vafa–Intriligator formula. In this setting, we compare the Quot scheme invariants with those obtained via the stable map compactification.

  • The size of t-cores and hook lengths of random cells in random partitions.
    with Arvind Ayyer
    Ann. Appl. Probab. 33 (2022) | arXiv:1911.03135v3
    Abstract

    Fix t ≥ 2. We first give an asymptotic formula for certain sums of the number of t-cores. We then use this result to compute the distribution of the size of the t-core of a uniformly random partition of an integer n. We show that this converges weakly to a gamma distribution after dividing by √n. As a consequence, we find that the size of the t-core is of order √n in expectation. We then apply this result to show that the probability that t divides the hook length of a uniformly random cell in a uniformly random partition equals 1/t in the limit. Finally, we extend this result to all residue classes modulo t using abacus representations for cores and quotients.

  • Random t-Cores and Hook Lengths in Random Partitions.
    with Arvind Ayyer
    Sém. Lothar. Combin. 84B (2020)
  • Driving chemical reactions with polariton condensates.
    with Sindhana Pannir-Sivajothi, Jorge A. Campos-Gonzalez-Angulo, Luis A. Martínez-Martínez, Joel Yuen-Zhou
    Nat. Commun. 1645 (2022) | arXiv:2106.12156
    Abstract

    When molecular transitions strongly couple to photon modes, they form hybrid light–matter modes called polaritons. Collective vibrational strong coupling is a promising avenue for chemical control, but this can be hindered by the large number of quasi-degenerate dark modes. The macroscopic occupation of a single polariton mode by excitations, as observed in Bose–Einstein condensation, offers a possible route to overcoming this issue. Here we theoretically investigate the effect of vibrational polariton condensation on the kinetics of electron transfer processes. Compared with excitation using infrared laser sources, the condensate significantly alters the reaction yield due to additional channels with reduced activation barriers arising from the large accumulation of energy in the lower polariton and the many modes available for energy redistribution during the reaction. Our results suggest new opportunities to use condensates to drive chemical reactions, kinetically bypassing usual constraints of fast intramolecular vibrational redistribution in the condensed phase.

  • Numerical invariants of Quot schemes of curves.
    Ph.D. Thesis (2023)
Shubham Sinha's face

Teaching

  • Algebraic Geometry: Spring 2026, ICTP
  • Complex Analysis: Fall 2024, ICTP
  • Calculus 1 (Math 10A): Summer 2023, UC San Diego
  • Calculus 2 (Math 10B): Summer 2022, UC San Diego
  • Calculus 2 (Math 10B): Summer 2021, UC San Diego

Students

  • Amar Aldakheel (Diploma program ICTP 24-25)
    Thesis: Vector Bundles and Topological K-Theory
  • Aubert Voalaza Mahavily Romuald (Diploma program ICTP 24-25)
    Thesis: Lie Groups and Lie Algebras: Curvature and Representations

Outreach

  • Olympiad: I was involved in training the Indian IMO (International Mathematical Olympiad) team during the years 2014-2017 and 2021.
  • Mentoring at UCSD: RTG graduate directed reading for undergraduates, Algebraic curves and Riemann surfaces, Spring 2021.
  • Mentoring at UCSD: RTG graduate directed reading for undergraduates, 27 lines on a cubic surface, Spring 2020.
Shubham Sinha's face

Research Talk

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Seminars