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

Date and Time: Tuesday, February 06, 2007, 12:15 pm

Duration: This information is not available in the database

Location: OAT S15/S16/S17

Speaker: Alexander Engström (KTH Stockholm)

A proof of a conjecture of Björner on simplicial polytopes

The f-vector of a polytope is a list of the number of faces by dimension. The g-theorem states that there is a bijection between the possible f-vectors of d dimensional simplicial polytopes and the M-sequences of length d/2+1. This bijection is a linear transformation and can be defined by a (d/2+1)x(d+1)-matrix which is usually denoted M_d. Björner proved that all 2x2 minors of M_d are nonnegative and derived a comparison theorem for f-vectors of simplicial polytopes. He conjectured that all minors of M_d are nonnegative and I will explain how this can be proved by considering some weighted planar graphs.

Joint work with Michael Björklund.

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