Caltech/USC Algebra & Geometry Seminar

Welcome to the homepage of the joint algebra and geometry seminar at California Institute of Technology and University of Southern California! We meet biweekly on Thursday afternoons, alternating between the two campuses. Each meeting consists of two one-hour talks followed by a seminar dinner. Topics at our seminar include but are not limited to algebra, representation theory, algebraic geometry, mirror symmetry, and mathematical physics.

  • Time: Thursdays 2:45pm-3:45pm and 4:00pm-5:00pm
  • (different from last semester)
  • Caltech location: Linde Hall (37), Room 187
  • USC location: Kaprelian Hall, Room 427. Note the room has changed.
  • Organizers: Yifeng Huang (USC), Wenyuan Li (USC), Weihong Xu (Caltech)
  • Click on the title to view the abstract.
  • Note the special date, time, and/or location in red, if any.

Below is the Winter and Spring 2024-2025 schedule. For Fall 2024-2025, see here. For the academic year 2024-2024, see here.

Date Speaker Affliation Title
1/16/2025
@USC
Siyang Liu USC
Symplectic Aspects of Hyperplane Arrangements

Abstract. Complexified complement of hyperplane arrangements are one of the most classical examples of study in singularity theory and algebraic geometry, while its symplectic properties are largely under exploration. In this talk, I’ll present our recent progress toward understanding symplectic geometry of hyperplane arrangements, which is connected to torus-equivariant topology of toric hyperKahler varieties. This is based on the recent joint work with Sukjoo Lee, Yin Li and Cheuk Yu Mak and work in preparation with Sheel Ganatra, Wenyuan Li and Peng Zhou.

Paolo Aluffi Florida State
Segre classes and Lorentzian/covolume polynomials

Abstract. Lorentzian polynomials provide a natural generalization of log-concave sequences and have had striking applications to deep conjectures in combinatorics, in work of June Huh and others. We will define a class of closely related polynomials, `covolume polynomials’, and explore situations in intersection theory in which they occur naturally, specifically, their appearance in the context of Segre classes of subschemes of products of projective spaces. We will also describe an application of these considerations to the combinatorics of convex polyhedral cones.

2/13/2025
@Caltech
Dragos Oprea UCSD
Cycles on the moduli space of abelian varieties

Abstract. The tautological ring of the moduli space of abelian varieties was introduced and computed by van der Geer in the 1990s. I will explain recent progress regarding the existence of non tautological classes on the moduli space of abelian 6-folds. This is based on joint work with Samir Canning and Rahul Pandharipande. 

Felix Thimm UBC
CY3 Wall-Crossing using Virtual Classes

Abstract. Wall-crossing in enumerative geometry allows us to vary the counting problem and compare the resulting generating series with the original one. It has emerged as a powerful tool for computations and in the study of properties of generating series. In this talk, I will introduce wall-crossing based on some interesting applications and present some new developments, which allow wall-crossing in a more general context using localization of virtual classes. This is based on joint work with Nick Kuhn and Henry Liu.

2/27/2025
@USC
KAP 427
Wern Yeong UCLA
A hyperbolicity conjecture for adjoint bundles

Abstract. A complex manifold X is said to be Brody hyperbolic if it admits no entire curves, which are non-constant holomorphic maps from the complex numbers. When X is a smooth complex projective variety, Demailly introduced an algebraic analogue of this property known as algebraic hyperbolicity. We propose a conjecture on the algebraic hyperbolicity of generic sections of adjoint bundles on X, motivated by Fujita’s freeness conjecture and recent results by Bangere and Lacini on syzygies of adjoint bundles. We present some old and new evidence supporting this conjecture, including when X is any smooth projective toric variety or Gorenstein toric threefold. This is based on joint work with Joaquín Moraga.

Song Yu Tsinghua YMSC
Remodeling Conjecture with descendants

Abstract. The Remodeling Conjecture of Bouchard-Klemm-Mariño-Pasquetti obtains all-genus open-closed Gromov-Witten invariants of a toric Calabi-Yau 3-fold from Chekhov-Eynard-Orantin topological recursion on the mirror curve. In this talk, I will discuss an extension of this framework to descendant mirror symmetry, that is, the all-genus descendant Gromov-Witten invariants can be obtained from the Laplace transform of topological recursion invariants. The result is based on a correspondence between equivariant line bundles supported on toric subvarieties and relative homology cycles on the mirror curve, which provides an identification of integral structures. I will also discuss an application to Hosono’s conjecture if time permits. This talk is based on joint work in progress with Bohan Fang, Chiu-Chu Melissa Liu, and Zhengyu Zong.

4/3/2025
@Caltech
Soham Karwa Duke
Non-archimedean periods for log Calabi-Yau surfaces

Abstract. Period integrals are a fundamental concept in algebraic geometry and number theory. In this talk, we will study the notion of non-archimedean periods as introduced by Kontsevich and Soibelman.  We will give an overview of the non-archimedean SYZ program, which is a close analogue of the classical SYZ conjecture in mirror symmetry. Using the non-archimedean SYZ fibration, we will see how non-archimedean periods recover the complex analytic periods for log Calabi-Yau surfaces, verifying a conjecture of Kontsevich and Soibelman. This is joint work with Jonathan Lai.

Irit Huq-Kuruvilla Virginia Tech
Quantum K Rings of Partial Flags, Coulomb Branches, and the Bethe Ansatz.

Abstract. There are two major predictions for the quantum K-ring of a partial flag: One comes from quantum field theory, where the ring is the OPE ring associated to a 3D GLSM. The other comes from work identifying the quasimap version of the ring with the Bethe algebra associated to a quantum integrable system. These predictions have a mysterious set of equations in common, which can be regarded as a special case of Nekrasov-Shatashvili's gauge/Bethe correspondence. We give a purely geometric explanation for this coincidence in terms of the abelian/non-abelian correspondence and use it to prove both sets of predictions.

4/10/2025
@Caltech
Shubham Sinha ICTP
TBA

Abstract. TBA.

Dori Bejleri U Maryland
TBA

Abstract. TBA

4/17/2025
@Caltech
Hannah Larson Berkeley
TBA

Abstract. TBA.

Bernd Sturmfels Berkeley
Gram Matrices for Isotropic Vectors

Abstract. We discuss determinantal varieties for symmetric matrices that have zero blocks along the main diagonal. In theoretical physics, these arise as Gram matrices for kinematic variables in quantum field theories. We also explore the ideals of relations among functions in the matrix entries that serve as building blocks for conformal correlators.

5/1/2025
@USC
KAP 427
José Yáñez UCLA
Polarized endomorphism of log Calabi-Yau pairs

Abstract. An endomorphism on a normal projective variety X is said to be polarized if the pullback of an ample divisor A is linearly equivalent to qA, for some integer q>1. Examples of these endomorphisms are naturally found in toric varieties and abelian varieties. Indeed, it is conjectured that if X admits a polarized endomorphism, then X is a finite quotient of a toric fibration over an abelian variety. In this talk, we will restrict to the case of log Calabi-Yau pairs (X,B). We prove that if (X,B) admits a polarized endomorphism that preserves the boundary structure, then (X,B) is a finite quotient of a toric log Calabi-Yau fibration over an abelian variety. This is joint work with Joaquin Moraga and Wern Yeong.

Reginald Anderson Claremont McKenna
Enumerative invariants of derived categories

Abstract. Following Kalashnikov, we recover Givental's small J function for CP^1 by viewing it as a toric quiver variety.