Algebraic, Topological and Complexity Aspects of Graph Covers
& Winter School in Harmonic Functions on Graphs and Combinatorial Designs

January 20 - 24, 2014

The workshop's main focus is on graph coverings and their applications in different areas of theoretical computer science such as models of computation, computational complexity, and algebraic graph theory. The aim of the workshop is to bring together researchers working on these diverse ends of graph coverings, to introduce their approaches and results to one another, and to try to pursue joint research combining these areas. Towards this end we plan a small number of survey talks, several open problem sessions, and ample time for discussions and problem solving...

Part of the program will consists of a series of introductory lectures on harmonic functions on graphs and on combinatorial designs aimed at PhD. students and young researchers.

This is already the sixth workshop in the ATCAGC series and is organized by:

  • Czech Mathematical Society, section of The Union of Czech Mathematicians and Physicists (JCMF)
  • Slovak Mathematical Society, section of The Union of Slovak Mathematicians and Physicists (JSMF)
  • Matej Bel University, Banska Bystrica
  • Department of Applied Mathematics, Charles University, Prague

Previous workshops were held in:

  • Bovec, Slovenia, 2013
  • Eugene, Oregon, 2012
  • Kralova Studna, Slovakia, 2011
  • Auckland, New Zealand, 2010
  • Finse, Norway, 2009

The conference photo.

More photos on picasa.

ATCAGC Talks & Contributions

Invited talks:
  • Rotary and regular maps with simple underlying graphs Marston Conder, University of Auckland, New Zealand
  • A regular map is a symmetric embedding of a graph (or multigraph) on some closed surface. This talk concerns the genus spectrum for such maps on orientable surfaces, with SIMPLE underlying graph. It is known that for some positive integers g, there is no orientably-regular map of genus g for which both the map and its dual have simple underlying graph, and also that for some g, there is no such map (with simple underlying graph) that is reflexible.
    I will show how families of covers of graphs/maps can be used to prove that that for over 83\% of all positive integers g, there exists at least one orientably-regular map of genus g with simple underlying graph. This is joint work with my former PhD student Jicheng Ma. We conjecture that there exists at least one such map for every positive integer g.

    Link to video showing pictures of regular maps, created by Jarke van Wijk (Eindhoven)
  • Covering constructions of extremal graphs of given degree and diameter, or girth Jozef Siran, Slovak University of Technology, Bratislava, Slovak Republic
  • The degree-diameter problem is to determine the largest order of a graph \linebreak of a given maximum degree and diameter. The related problem of determination of the smallest order of a graph of a given degree and girth is sometimes called the degree-girth problem. In both cases our knowledge about the actual maxima/minima is rather limited. Nevertheless, there are a number of interesting bounds on these parameters obtained by constructions.
    It turns out that a considerable proportion of the largest currently known graphs of given degree and diameter, and the smallest known graphs of given degree and girth, have been or can be obtained as lifts of small base graphs with voltages in groups with a fairly simple structure. In the talk we will give a survey of these constructions and outline open problems in this area of research.


Winter School Lectures

Topics and Speakers

All Talks, Abstracts and Presentations


Registration & Fees

To register, please fill in the registration form here.
The registration fee covers conference admission and materials, accomodation and full board starting by Sunday dinner and ending by Friday lunch. Program begins Monday morning, therefore participants are expected to arrive on Sunday evening.

Fees for early registration - before December 20, 2013:

  • 450 EUR for accommodation in a single room
  • 350 EUR for accommodation in a double room
  • 280 EUR for students (a double room, or a bungalow (= two double rooms & a living room, for 3-4-member groups)

For bank transfers use the following account informations. Transfers should be delivered by Jan 10, otherwise will be collected in chash at the workshop. Please make sure that the payment will be delivered free of all international transfer fees.

IBAN CZ22 0800 0000 0002 0003 0319
Bank addressCeska sporitelna, pobocka Praha 8, Sokolovska 1, 186 53, Praha 8, Czech Republic
Account holderJednota ceskych matematiku a fyziku - CMS
Account number
for domestic transfers
The payment identification number will be sent to you by the organizers.

For late registration (on or after December 21, 2013) extra 50 EUR will be charged.

All the expenses will be covered for the members of the grant mobility project: "Mobility -- Enhancing Research, Science and Education" ITMS code: 26110230082, under the Operational Programme Education cofinanced by the European Social Fund.

We offer to cover the registration fee (including accomodation and board) for a limited number of PhD. students and postdocs interested to take part in the winter school courses. To get support it is necessary to register and write an extra e-mail to Roman Nedela (nedela at


Accomodation & Travel Info

Address: Hotel Sepetna, Ostravice 0956, 739 14 Ostravice, Czech Republic.

Hotel Sepetna is located at Beskydy mountains, on Czechoslovak border about 4 hours of drive/train from Pargue or Vienna.

Group transportation to and from the workshop will be offered from Prague.



Jiri Fiala, Jan Kratochvil, Roman Nedela, Michaela Seifrtova