CoM | Slicing Pizzas and Counting Necklaces

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Tuesday, July 21, 2026
 – Live Presentation with
Joel Haddley–

Session at 12 Noon Atlanta time
(check your time here)

Please join us starting 10 minutes before this session using the following button.

CoM Zoom Event

For published CoM presentations please visit the G4G YouTube channel

After this virtual CoM presentation on Zoom, we will meet for an informal social session in a different Zoom space where we can all see each other (see the blue button below).  That Zoom meeting will start around 1pm ET.

Please join the social using the following button:

ZOOM Social Meeting

Slicing Pizzas and Counting Necklaces

Is it possible to cut a pizza into congruent slices so that at least one slice does not touch the centre? This deceptively simple puzzle leads to a rich collection of geometric and combinatorial questions. In this talk, we will present several constructions and the ideas behind them, explore how necklace numbers arise naturally in the combinatorics of the dissections, and finish with a selection of open problems.

Dr Joel Haddley completed his PhD in 2011 under the supervision of Prof Victor Goryunov, studying classes of unimodal singularities and how they can be associated with complex hyperbolic reflection groups. He is a Senior Lecturer at The University of Liverpool, where his work now focuses on mathematics education and scholarship. He also serves as Deputy Chair of the Higher Education Committee of the Institute of Mathematics and its Applications.

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