# LSV Seminar

The LSV seminar takes place on Tuesday at 11:00 AM. The usual location is the conference room at Pavillon des Jardins (venue).
If you wish to be informed by e-mail about upcoming seminars, please contact Stéphane Le Roux and Matthias Fuegger.

The seminar is open to public and does not require any form of registration.

## Past Seminars

### Games of ordinal Length

- Date
- Monday, April 06 2009 at 11:00AM
- Place
- Salle de Conférence (Pavillon des Jardins)
- Speaker
- Florian Horn (CWI, Amsterdam)

We present an extension of the classical model of infinite two-player games,
allowing plays with arbitrary ordinal length. In addition to the usual
''successor transitions'', our arenas feature ''limit transitions'' which
describe what happens after partial plays whose length is a limit ordinal. The
play only stops when it reaches a final state, which can be winning for either
of the players.

We describe two solutions for such games. The first one uses a reduction to
infinite Muller games, and shows that the problem of the winner is
PSPACE-complete. The second one uses a special case of ordinal games with
''priority'' transitions, where the players have positional strategies. A
LAR-like construction allows us to derive the existence of finite-memory
strategies in the general case.