News archive


Differential geometry seminar - December 2, 10am, lecture room M5 PDF Print

The seminar on differential geometry will continue with this lecture:

December 2, 10am, lecture room M5.

Vincent Pecastaing (University of Luxembourg):

Actions of higher-rank lattices on conformal and projective structures

Abstract:

The main idea of Zimmer's program is that in real-rank at least 2, the rigidity of lattices of semi-simple Lie groups makes that their actions on closed manifolds are understandable. After a short survey giving a more precise idea of Zimmer's conjectures and their context, I will give recent results about conformal and projective actions of cocompact lattices. The fact that these geometric structures do not carry a natural invariant volume is one of the main motivations. We will see that the real-rank is bounded above like when the ambient Lie group is acting, and that at the critical value, the manifold is globally isomorphic to a model homogeneous space. The proofs rely in part on an "invariance principle" recently introduced by Brown, Rodriguez-Hertz and Wang, which guarantees the existence of finite invariant measures in some dynamical context.

Last Updated on Friday, 29 November 2019 14:38
 
Differential equations seminar - December 2, 12pm, lecture room M5 PDF Print

Seminar of differential equations will continue on December 2, 2019 at 12pm in lecture room M5.

Dr. Rotchana Chieochan (Khon Kaen University, Thajsko)

Floquet theory for q-difference equations

Abstract:

In this talk, we introduce q-periodic functions in quantum calculus and study the first-order linear q-difference vector equation for which its coefficient matrix function is q-periodic and regressive. Based on the new definition of periodic functions, we establish Floquet theory in quantum calculus.

Last Updated on Tuesday, 26 November 2019 12:03
 
Algebra seminar - November 28, 1pm, lecture room M5 PDF Print

We will continue on Thursday, November 28, in M5 at 1pm by the talk

J. R. Gonzales

Grothendieck categories and their tensor product as filtered colimits


Abstract:
Grothendieck categories are the Ab-enriched Grothendieck topoi. In this talk, we will first show two different ways to obtain a Grothendieck category as a filtered colimit of its representing linear sites: one given by all possible representing linear sites, the other, coarser, given by the representing linear sites induced by the full subcategories of alpha-presentable objects, with varying regular cardinal alpha. Making use of the latter, we show that the tensor product of Grothendieck categories, introduced in previous joint work with Lowen and Shoikhet, is compatible via this construction with Kelly's alpha-cocomplete tensor product. This allows us to translate the functoriality, simmetry and commutativity of Kelly's tensor product to the tensor product of Grothendieck categories.

Last Updated on Monday, 25 November 2019 16:15
 
Differential geometry seminar - November 18, 10am, lecture room M5 PDF Print

The seminar on differential geometry will continue with this lecture:

November 18, 10am, lecture room M5.

Hanci Chi (McMaster University/UHK University):

Invariant Einstein Metrics of Cohomogeneity One with Principal Orbits as Wallach Spaces

Abstract:

A Riemannian manifold (M, g) is Einstein if its Ricci tensor is a constant multiple of g. With its charm and influence in both mathematics and physics, the subject of Einstein metrics draws a great amount of attention from both communities. In this talk, we give an introduction to Einstein metrics of cohomogeneity one. Its construction reduces the Einstein equations to a system of ODEs. Then we introduce some new examples. They are vector bundles M whose principal orbit G/K are Wallach spaces. On each M, we found a 1-parameter continuous family of Ricci-flat metrics and a 2-parameter continuous family of negative Einstein metrics. In particular, the complete metric with G2 holonomy discovered by Robert Bryant and Simon Salamon is recovered in the construction.

Last Updated on Thursday, 14 November 2019 10:29
 
Differential equations seminar - November 18, 12pm, lecture room M5 PDF Print

Seminar of differential equations will continue on November 18, 2019 at 12pm in lecture room M5.

doc. Mgr. Pavel Řehák, Ph.D. (Ústav matematiky, FSI VUT Brno)

Asymptotic analysis of differential and difference equations

Last Updated on Thursday, 14 November 2019 10:34
 
«StartPrev12345678910NextEnd»

Page 1 of 26