Differential geometry seminar  December 2, 10am, lecture room M5 


The seminar on differential geometry will continue with this lecture:
December 2, 10am, lecture room M5.
Vincent Pecastaing (University of Luxembourg):
Actions of higherrank lattices on conformal and projective structures
Abstract:
The main idea of Zimmer's program is that in realrank at least 2, the rigidity of lattices of semisimple 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 realrank 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, RodriguezHertz 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 


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 qdifference equations
Abstract:
In this talk, we introduce qperiodic functions in quantum calculus and study the firstorder linear qdifference vector equation for which its coefficient matrix function is qperiodic 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 


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 Abenriched 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 alphapresentable 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 alphacocomplete 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 


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 1parameter continuous family of Ricciflat metrics and a 2parameter 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 


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 

