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19
votes
Examples of concrete games to apply Borel determinacy to
The game of infinite Hex, proceeding from an arbitrary position, is a good example with all the features you seek. The game was the subject of my Oxford student Davide Leonessi's masters MFoCS dissert …
7
votes
Negative of combinatorial game
No, the negative a game is simply the game in which the player's roles are swapped, hereditarily. You can see this in the definition you provided
$$-G=\{ -G^R\mid -G^L\}$$
since the left options in $- …
7
votes
Who wins infinite Hex?
This doesn't answer the question that was asked, but rather an alternative kind of infinite Hex, played on the infinite hexagonal lattice board as shown below. I am posting it because people intereste …
9
votes
JUSTICE & INJUSTICE — two 2-player finite games
Here is a complete winning strategy for the Justice game.
One wins the Justice game simply by following the usual Nim strategy, with all the same winning positions and moves (except if the position is …
3
votes
Accepted
Is following function a metric on the set of isomorphism classes of graphs with countably ma...
To prove that this is a metric, consider the following theorem.
Theorem. If the second player can survive for $n$ steps in the $(\Gamma_1,\Gamma_2)$ game, and for $m$ steps in the $(\Gamma_2,\Gamma_3 …
16
votes
Who first chose the names Alice and Bob for players A and B?
Allow me to mention that since the players in effect adopt the roles of the quantifiers $\forall$ and $\exists$, as Bob has a winning strategy just in case for every move for Alice, there is a reply b …
20
votes
Accepted
Forcing and Family Contentions: Who wins the disputes?
I like this question a lot. It provides an interesting way of talking about
some of the ideas connected with the maximality principle and the
modal logic of forcing.
Let me make several observations. …
16
votes
Alice and Bob playing on a circle
For even $n$, I claim that nobody has a winning strategy, and therefore both players have drawing strategies.
To see this, observe first that by the fundamental theorem of finite games, we know that …
4
votes
When is a game tree the game tree of a board game?
Here is one possible answer. An essential feature of any board game, in the way I am thinking about it, is that there are only finitely many game states that are realizable on the board. This fact, co …
19
votes
5
answers
1k
views
When is a game tree the game tree of a board game?
This question arises from what I find interesting in the recently
asked question What is a chess piece
mathematically?
My answer to that question was that mathematically, game pieces are
in general e …
14
votes
Accepted
Determined, finite games
There are numerous proofs of what I call the fundamental theorem of finite
games.
Theorem. (Fundamental theorem of finite games)
In any finite two-player game of perfect information, one of the pla …
6
votes
Determinacy of (infinite, possibly loopy) combinatorial games
This amounts to the Gale-Stewart theorem showing that open games are determined. The issue of draws can be easily finessed, as I explain below.
Specifically, a game of perfect information is open for …
0
votes
Are sums of 0-1 Pareto efficient vectors Pareto efficient?
Unless I have misunderstood, here is a counterexample. Let $A$ be the $2\times 2$ identity matrix. This has your Pareto property on $x-y$, but if $x=[{a\atop b}]$, then $Ax=x$, and there is no way to …
11
votes
Accepted
Explicit examples of undetermined games
Here is an amusing concrete non-determined game, under the assumption that the dependent choice principle fails.
Assume DC fails. This means that there is a set $X$ and a binary relation $R$ on $X$, …
6
votes
$n$-in-a-row game on $\mathbb{R}^2$
I'll start things off by observing that this is what is known as an open game, since if player 1 wins, then the winning condition is satisfied after finitely many moves. It follows by the Gale-Stewart …