The seminar on differential geometry will continue by the following lecture:

November 5 (10.00, M5)

Radoslaw Kycia:

Integrability of geodesics of totally geodesic metrics

Abstract:

Analysis of the geodesics in the space of signature (1,3) that splits in two-dimensional distributions resulting from the Weyl tensor eignespaces - hyperbolic and elliptic ones will be presented. Similar model of General Theory of Relativity coupled to Electromagnetism will be explained. Analysis of geodesic integrability will be outlined. This will be the brief overview of the manuscript [1].

Bibliography: [1] R. A. Kycia, M. Ułan, Integrability of geodesics of totally geodesic metrics, https://arxiv.org/abs/1810.00962

The seminar on differential geometry will continue by the following lecture:

November 12 (10.00, M5)

Artur Sergyeyev (SU Opava)

Hydrodynamic Integrability: from Symplectic to Contact Geometry

Abstract:

We begin with a brief introduction to integrable systems in general and a review of known results on the construction of integrable hydrodynamic-type partial differential systems in three independent variables with Lax pairs involving Hamiltonian vector fields. Then we present a generalization of this construction to the case of four independent variables, where Hamiltonian vector fields are replaced by contact ones, and show that this approach gives rise to a large new class of integrable hydrodynamic-type systems.

Next algebra seminar: November 8, in M5 at 13.00.

Jovana Obradović (Charles University Prague)

Categorified cyclic operads in nature

Abstrakt:

In this talk, I will introduce a notion of categorified cyclic operad and justify the need of such a notion by exhibiting its place and use “in nature”.
Categorified cyclic operads are like symmetric monoidal categories, in that they guide an interplay of commutativity and associativity, but they are more restrictive, as they allow less instances of these two isomorphisms. In particular, the coherence conditions of symmetric monoidal categories do not ensure coherence of categorified cyclic operads, the hexagon of Mac Lane not even being well-defined in the latter setting. The coherence conditions that we do take from Mac Lane are the pentagon and the requirement that the commutator isomorphism is involutive, but we need much more in order to ensure coherence: we need two more mixed coherence conditions, a hexagon (which is not the hexagon of Mac Lane) and a decagon, as well as three more conditions which deal with the action of the symmetric group.
I will first give an example of a categorified cyclic operad in the form of an easy generalisation of the structure of profunctors of Bénabou.
I will then show how to exploit the coherence conditions of categorified cyclic operads in proving that the Feynman category for cyclic operads, introduced by Kaufmann and Ward, admits an odd version.
I will finish with combinatorial aspects of categorified cyclic operads, i.e. with their possible characterisations in convex and discrete geometry. This investigation aims at finding polytopes which describe the coherences of categorified cyclic operads, in the same was as the geometry of symmetric monoidal categories is demonstrated by permutoassociahedra.

Seminar of differential equations will continue on November 5, 2018 at 12pm in lecture room M5.

Mgr. Jana Burkotová, Ph.D.

Periodic bouncing solutions of singular second order ODE.