Explicit complete Calabi-Yau metrics and Kähler-Ricci solitons

Speaker: 

Charles Cifarelli

Institution: 

SUNY Stonybrook

Time: 

Tuesday, November 26, 2024 - 4:00pm

Host: 

Location: 

RH306

Since Calabi's original paper, the Calabi Ansatz has been central for constructions in Kähler geometry. Calabi himself used it to construct complete Ricci-flat metrics on the total space of the canonical bundle of a Kähler-Einstein Fano manifold (B, \omega_B), generalizing some well-known examples coming from physics. Over the years, work of Koiso, Cao, Feldman-Ilmanen-Knopf, Futaki-Wang, Chi Li, and others have shown that the Calabi Ansatz can be used to produce complete Kähler-Ricci solitons, important singularity models for the Kähler-Ricci flow, on certain line bundles over (B, \omega_B). In this talk, I'll explain a generalization of these results to the total space of some higher-rank direct-sum vector bundles over (B, \omega_B). In our case the Calabi Ansatz is not suitable, and we instead use the theory of hamiltonian 2-forms, introduced by Apostolov-Calderbank-Gauduchon-Tønneson-Friedman. The construction produces new examples of complete shrinkers, steadies, and Calabi-Yau metrics, as well as recovering some known ones.

Pluriclosed manifolds with parallel Bismut torsion and the pluriclosed flow

Speaker: 

Giuseppe Barbaro

Institution: 

Aarhus University

Time: 

Tuesday, November 19, 2024 - 4:00pm

Host: 

Location: 

RH306

We present a complete classification of simply-connected pluriclosed manifolds with parallel Bismut torsion. Consequently, we also establish a splitting theorem for compact manifolds that are both pluriclosed with parallel Bismut torsion and have vanishing Bismut Ricci form. Due to the relations of these conditions with the Vaisman geometry, we also analyze the behavior of the pluriclosed flow, proving that it preserves the Vaisman condition on compact complex surfaces if and only if the starting metric has constant scalar curvature.

On 4d Ricci-flat metrics with conformally Kähler geometry

Speaker: 

Mingyang Li

Institution: 

UC Berkeley

Time: 

Tuesday, October 29, 2024 - 4:00pm

Host: 

Location: 

RH306

Ricci-flat metrics are fundamental in differential geometry, and they are easier to study when they have additional structures. I will describe my works on 4d non-trivially conformally Kähler Ricci-flat metrics, which actually is a very natural class of 4d Ricci-flat metrics. This leads to a classification of asymptotic geometries of such metrics at infinity and a classification of such gravitational instantons

Symmetry of Kahler Gradient Ricci Solitons

Speaker: 

Hung Tran

Institution: 

Texas Tech University

Time: 

Tuesday, October 15, 2024 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

Kahler Gradient Ricci Solitons (KGRS) are fundamental in the theory of Ricci flows. This talk's focus is on complex dimension two and will first review the recent beautiful classification of the shrinking possibly non-compact case. Then we'll discuss an approach to detect symmetry applicable to all cases. This differs from and should complement the popular perspective based on asymptotic behaviors. The idea is inspired by Morse-theoretic aspects of symplectic geometry and involves the understanding of singular sets of a moment map. Precisely, we'll show that a KGRS in complex dimension two is an integrable Hamiltonian system; if the system is generic, then it admits a holomorphic 2-torus action.

Bogomolov-Gieseker inequality for log terminal Kahler threefolds

Speaker: 

Henri Guenancia

Institution: 

Université Paul Sabatier

Time: 

Tuesday, October 22, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

In this joint work with Mihai Paun, we show that a so-called Q-sheaf on a log terminal Kahler threefold satisfies a suitable Bogomolov-Gieseker inequality as soon as it is stable with respect to a Kahler class. I will discuss the strategy of the proof as well as some applications if time permits.

(Weighted) cscK metrics

Speaker: 

Eleonora Di Nezza

Institution: 

Sorbonne Université and Ecole Normale Superieure

Time: 

Tuesday, December 3, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH306

A central theme in Kähler geometry is the search for canonical Kähler metrics, such as Kähler-Einstein metrics, constant scalar curvature Kähler (cscK for short) metrics, extremal metrics, Kähler-Ricci solutions, etc. The concept of weighted cscK metrics, introduced by Lahdili in 2019, provides a unification of all the above geometric settings. In this talk I will give a panorama of what it is known about these metrics and I will present a criteria for ensuring their existence. This is a joint work with S. Jubert and A. Lahdili.

A family of Kahler flying wing steady Ricci solitons

Speaker: 

Ronan Conlon

Institution: 

University of Texas, Dallas

Time: 

Tuesday, November 12, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

Steady Kahler-Ricci solitons are eternal solutions of the Kahler-Ricci flow. I will present new examples of such solitons with strictly positive sectional curvature that live on C^n and provide an answer to an open question of H.-D. Cao in complex dimension 2. This is joint work with Pak-Yeung Chan and Yi Lai.

The (spherical) Mahler measure of the X-discriminant

Speaker: 

Sean Paul

Institution: 

University of Wisconsin, Madison

Time: 

Tuesday, October 1, 2024 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

Let P be a homogeneous polynomial in N+1 complex variables of degree d. The logarithmic Mahler Measure of P (denoted by m(P) ) is the integral of log|P| over the sphere in C^{N+1} with respect to the usual Hermitian metric and measure on the sphere.  Now let X be a smooth variety embedded in CP^N by a high power of an ample line bundle and let $\Delta$ denote a generalized discriminant of X wrt the given embedding , then $\Delta$ is an irreducible homogeneous polynomial in the appropriate space of variables.  In this talk I will discuss work in progress whose aim is to find an asymptotic expansion of m(\Delta) in terms of elementary functions of the degree of the embedding.  

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