Algebra seminar  February 13, 1pm, lecture room M5 


We will continue on Thursday, February 13, in M5 at 1pm by the talk
F. Pakhomov
Dilators and Ptykes
Abstract: Dilators are endofunctors D:WO>WO preserving pullbacks and directed colimits, where WO is the category of wellorderings and strictly monotone maps. This notion was introduced by J.Y. Girard as one of central notions within his approach to certain problems in prooftheory (calculation of prooftheoretic ordinals). Some more sophisticated applications motivate higherorder generalizations of the notion of dilator, known as ptykes. For example, ptykes of the type (WO>WO)>WO are functors from the category of dilators Dil to WO that preserve pullbacks and directed colimits (here Dil is the category of dilators and Cartesian natural transformations). In the first part of the talk I plan to discuss dilators, some basic results about them, and give some idea about their applications in prooftheory. Next I plan to talk about my approach to the theory of ptykes, where types of ptykes are interpreted as classes of relational structures that are closed under substructures. 
Last Updated on Thursday, 06 February 2020 16:13 

28th mathematical hike  January 25th 2020 


Dear Friends of Hikes and Mathematics,
you are invited to our 28th mathematical hike planned on January 25th. Meet at 09:36 at the bus stop "Veverská Bítýška, náměstí" (bus number 303). The hike is 18 km long  we will follow a green path to Lažánky and go a full circle by a yellow path to Bítýška. We will return to Brno by bus.
All information and photos can be found at http://conference.math.muni.cz/vylety/. (in CZ) Have a nice January and successful exam period, Jonatan Kolegar and Jana Bartoňová, organizers, Jan Slovák, Director of the Department of Mathematics and Statistics 
Last Updated on Thursday, 09 January 2020 16:36 
Algebra seminar  January 9, 1pm, lecture room M5 


We will continue on Thursday, January 9, in M5 at 1pm by the talk
S. Henry
Polygraphs and homotopy polygraphs
Abstract: Polygraphs (or computades) are the most general notion of diagram generating strict infinity categories. Some people have believed in the past that they were a presheaves category, but this was proved to be false by Makkai and Zawadowski. After a quick introduction to polygraphs and why they are not a presheaves category, I'll show that if one defines a homotopy theoretic (or infinity categorical) version of polygraphs then they form an infinity presheaves category. More generally I'll associate to any strongly cartesian monad acting on an infinity topos an infinity category of polygraphs which is itself an infinity topos. 
Last Updated on Tuesday, 07 January 2020 16:37 
MUNI Seminar series  Noga Alon  List Coloring 


December 18, 2019 from 4:30 PM at Refectory of Augustinian Abbey at Mendel Square  Mendel Museum
List Coloring
Abstract:
The list chromatic number of a graph G is the minimum k so that for every assignment of a list of k colors to any vertex of G there is a vertex coloring assigning to each vertex a color from its list so that adjacent vertices get distinct colors. This notion was introduced by Vizing and by Erdős, Rubin and Taylor in the late 70s and its study combines combinatorial, probabilistic and algebraic techniques.
Its natural extension to hypergraphs is closely related to questions in Euclidean Ramsey Theory. I will discuss several old and new problems and results in the area focusing on a recent work with Briceno, Chandgotia, Magazinov and Spinka motivated by questions in statistical physics regarding vertex colorings of the ddimensional lattice. 
Last Updated on Wednesday, 18 December 2019 12:01 
27th mathematical hike  December 14th 2019 


Dear Friends of Hikes and Mathematics,
you are invited to our 27th mathematical hike planned on December 14th. Meet at 09:36 at the bus stop "Rozcestí" (bus 57) in Útěchov. We have planned a short hike (not even 10 km) not following any tourist path towards the ruins of Ronov castle. The end of the hike is in Útěchov. Snow or mud, doesn't matter, look forward to a Christmas hike. All information and photos can be found at http://conference.math.muni.cz/vylety/. (in CZ) Have a nice December, Jonatan Kolegar and Jana Bartoňová, organizers, Jan Slovák, Director of the Department of Mathematics and Statistics 
Last Updated on Thursday, 12 December 2019 11:24 

