Transfinite Chomp

Jerry Shurman

In the game of Chomp, cookies are laid out at the lattice points $N^d$ with a poison cookie at the origin. Two players alternate biting into the configuration, each bite eating the cookies in an infinite box from some point outward in all directions, until someone loses by eating the poison cookie. The game can also start with finitely many bites already taken. This talk discusses Chomp extended to $\Omega^d$ (where $\Omega$ denotes the ordinals), a subject investigated by Scott Huddleston. Transfinite Chomp has satisfyingly complete results. In two dimensions, for example, a position of two columns of equal height $h$ loses for the player who reaches it if $h\in Z^+$, but it wins for the player who reaches it if $h=\omega$, and then it loses again for the player who reaches it if $h>\omega$. For three columns of height $h$, the position is a win for the player who reaches it if and only if $h=\omega^\omega$. In three dimensions, the box of height $h$ over a 2-by-2 base is a win for the player who reaches it if and only if $h=w^3$.