Energy-momentum inequalities in asymptotically anti-de Sitter spacetimes

Speaker: 

Naqing Xie

Institution: 

Fudan University and UC Irvine

Time: 

Tuesday, February 24, 2015 - 4:00pm to 5:00pm

Location: 

RH 306

We discuss certain inequalities for the Henneaux-Teitelboim total
energy-momentum for asymptotically anti-de Sitter initial data sets
which are asymptotic to arbitrary t-slice in anti-de Sitter spacetime. We
also give the relation between the determinant of the energy-momentum matrix
and the Casimir invariants. This is a joint work with Y. Wang and X. Zhang.

On the topology and index of minimal surfaces

Speaker: 

Davi Maximo

Institution: 

Stanford University

Time: 

Tuesday, February 3, 2015 - 4:00pm to 5:00pm

Location: 

RH 306

We show that for an immersed two-sided minimal surface in R^3,
there is a lower bound on the index depending on the genus and number of
ends. Using this, we show the nonexistence of an embedded minimal surface
in R^3 of index 2, as conjectured by Choe. Moreover, we show that the
index of an immersed two-sided minimal surface with embedded ends is
bounded from above and below by a linear function of the total curvature
of the surface. (This is joint work with Otis Chodosh)

Homology of curves and surfaces in closed hyperbolic 3-manifolds

Speaker: 

Yi Liu

Institution: 

Caltech

Time: 

Tuesday, November 25, 2014 - 4:00pm to 5:00pm

Location: 

RH 306

Closed quasi-Fuchsian subsurfaces of closed hyperbolic
3-manifolds constructed by J. Kahn and V. Markovic have played a crucial
role in the recent proof of the Virtual Haken Conjecture. In this talk, we
will investigate the techniques and construct homologically interesting
possibly bounded quasi-Fuchsian subsurfaces in closed hyperbolic
3-manifolds. We will focus on extending the geometric and topological
aspects from work of Kahn-Markovic, and will discuss further questions.
This is joint work with Vladimir Markovic.

Limits of Bott-Chern cohomology

Speaker: 

Baosen Wu

Institution: 

Harvard University

Time: 

Tuesday, December 9, 2014 - 4:00pm

Location: 

RH 306

Bott-Chern cohomology is a refinement of de Rham cohomology on
complex manifolds. We shall discuss the limit of Bott-Chern cohomology in
terms of hypercohomology for semistable degeneration of complex manifolds.
As an application, we show that nonkahler Calabi-Yau 3-folds obtained by
conifold transition satisfy d d\bar lemma, hence admit a Hodge decomposition.

Uniqueness and unique-continuation for geometric flows via energy methods

Speaker: 

Brett Kotschwar

Institution: 

Arizona State University

Time: 

Tuesday, November 11, 2014 - 4:00pm to 5:00pm

Location: 

RH 306

We describe a short, direct, alternative to the DeTurck trick to prove the
uniqueness of solutions to a large class of curvature flows of all orders,
including the Ricci flow, the L^2 curvature flow, and other flows related
to the ambient obstruction tensor. Our approach is based on the analysis
of simple energy quantities defined in terms of the actual solutions to the
equations, and allows one to avoid the step -- itself potentially
nontrivial in the noncompact setting -- of solving an auxiliary parabolic
equation (e.g., a k-harmonic-map heat-type flow) in order to overcome the
gauge-invariance-based degeneracy of the original flow. We also
demonstrate that, by the consideration of a certain energy
quotient/frequency-type quantity, one can give a short and quantitative
proof (avoiding Carleman inequalities) of the global backward uniqueness of
solutions to a large class of these equations.

Nevanlinna's Theory and Holomorphic Dynamics

Speaker: 

Nessim Sibony

Institution: 

University of Paris IV

Time: 

Tuesday, November 18, 2014 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

I will discuss some analogies between the second main

theorem in Nevanlinna's theory and results in holomorphic dynamics.

The two main examples will be equidistribution results for endomorphisms of $\P^k$ and

equidistribution results for singular foliations by Riemann-surfaces in $\P^2$.

 

This is joint work with T. C. Dinh.

Evans-Krylov type theorem for twisted Monge-Ampere equations

Speaker: 

Micah Warren

Institution: 

University of Oregon

Time: 

Tuesday, October 14, 2014 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

Motivated by the pluriclosed flow of Streets and Tian, we establish
Evans-Krylov type estimates for parabolic "twisted" Monge-Ampere
equations in both the real and complex setting. In particular, a bound
on the second derivatives on solutions to these equations yields bounds
on Holder norms of the second derivatives. These equations are
parabolic but neither not convex nor concave, so the celebrated proof of
Evans-Krylov does not apply. In the real case, the method exploits a
partial Legendre transform to form second derivative quantities which
are subsolutions. Despite the lack of a bona fide complex Legendre
transform, we show the result holds in the complex case as well, by
formally aping the calculation. This is joint work with Jeff Streets.

Minimal surfaces in the 3-sphere by stacking tori

Speaker: 

David Wiygul

Institution: 

UC Irvine

Time: 

Tuesday, December 2, 2014 - 4:00pm to 5:00pm

Location: 

RH 306

Kapouleas and Yang have constructed, by gluing methods, sequences of
minimal embeddings in the round 3-sphere converging to the Clifford
torus counted with multiplicity 2. Each of their surfaces, which
they call doublings of the Clifford torus, resembles a pair of
coaxial tori connected by catenoidal tunnels and has symmetries
exchanging the two tori. I will describe an extension of their work
which yields doublings admitting no such symmetries as well as
examples incorporating an arbitrary (finite) number of tori, that
is Clifford torus triplings, quadruplings, and so on.

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