Discrete Geometry and Combinatorics Seminar Autumn 2011

All seminars take place on Wednesdays at 4.00pm in Room 807 on the 8th floor of the Mathematics Dept. See how to find us for further details. There will be tea afterwards in room 606.

If you require any more information on these seminars please contact Dr John Talbot e-mail: talbot AT math.ucl.ac.uk or tel: 020-7679-4102.

02 November 2011

Chris Dowden (Polytechnique, Paris)

Extremal Planar Graphs

09 November 2011


Friday 18 November 2011

Oleg Pikhurko (Warwick)

Irrationality of the Turan Density


Let $\cal F$ be a family of $k$-graphs. The \emph{Tur\'an function $ex(n,F)$} is the maximum number of edges in an $\cal F$-free $k$-graph on $n$ vertices. The \emph{Tur\'an density $\pi(\cal F)$} is the limit of $ex(n,F)/{n\choose k}$ as $n$ tends to infinity. (The limit is known to exists for every $\cal F$.) 

We disprove the conjecture of Chung and Graham that $\pi(\cal F)$ is rational for every finite family $\cal F$. This conjecture was independently disproved by Rahil Baber and John Talbot.

23 November 2011

Jozef Skokan (LSE)

Ramsey theory for non-complete graphs

07 December 2011

Edgardo Roldan Pensado (UCL)

An extension of the Yao-Yao partition theorem