Mittagsseminar (in cooperation with J. Lengler, A. Steger, and D. Steurer)

Date and Time: Tuesday, February 20, 2007, 12:15 pm

Duration: This information is not available in the database

Location: OAT S15/S16/S17

Speaker: Florian Zickfeld (TU Berlin)

Counting Graph Orientations with Fixed Out-Degrees

Orientations of planar maps (that is planar graphs with fixed embeddings) with out-degrees given by a function α are called α-orientations. The concept of an α-orientation provides a unified approach to many structures such as Eulerian orientations, bipartite f-factors, Schnyder woods and bipolar orientations. For a given class of planar maps and out-degree functions we study the maximum number of α-orientations that can occur.

I explain how the number of α-orientations on a planar map with n vertices can be bounded from above by 3.73^n and introduce a family of plane graphs with 2.598^n α-orientations. I also present specialized bounds for the above mentioned structures. I then discuss a reduction to counting bipartite perfect matchings and known facts about the complexity of counting α-orientations. I conclude by posing some open problems.

Joint work with Stefan Felsner.

Upcoming talks     |     All previous talks     |     Talks by speaker     |     Upcoming talks in iCal format (beta version!)

Previous talks by year:   2024  2023  2022  2021  2020  2019  2018  2017  2016  2015  2014  2013  2012  2011  2010  2009  2008  2007  2006  2005  2004  2003  2002  2001  2000  1999  1998  1997  1996  

Information for students and suggested topics for student talks

Automatic MiSe System Software Version 1.4803M   |   admin login