Cauchy filters from Pelant's games

The language of finite games is used to rephrase Pelant's proof of his result: The separable modification of the complete metric space $C([0,\omega_1])$ is not complete.Comment: 6 page

Semipullbacks of labelled Markov processes

A labelled Markov process (LMP) consists of a measurable space $S$ together with an indexed family of Markov kernels from $S$ to itself. This structure has been used to model probabilistic computations in Computer Science, and one of the main problems in the area is to define and decide whether two LMP $S$ and $S'$ "behave the same". There are two natural categorical definitions of sameness of behavior: $S$ and $S'$ are bisimilar if there exist an LMP $T$ and measure preserving maps forming a diagram of the shape $S\leftarrow T \rightarrow{S'}$; and they are behaviorally equivalent if there exist some $U$ and maps forming a dual diagram $S\rightarrow U \leftarrow{S'}$. These two notions differ for general measurable spaces but Doberkat (extending a result by Edalat) proved that they coincide for analytic Borel spaces, showing that from every diagram $S\rightarrow U \leftarrow{S'}$ one can obtain a bisimilarity diagram as above. Moreover, the resulting square of measure preserving maps is commutative (a "semipullback"). In this paper, we extend the previous result to measurable spaces $S$ isomorphic to a universally measurable subset of a Polish space with the trace of the Borel $\sigma$-algebra, using a version of Strassen's theorem on common extensions of finitely additive measures.Comment: 10 pages; v2: missing attribution to Doberka

Cake Division by Majority Decision

We consider a collective choice process where three players make proposals sequentially on how to divide a given quantity of resources. Afterwards, one of the proposals is chosen by majority decision. If no proposal obtains a majority, a proposal is drawn by lot. We establish the existence of the set of subgame perfect equilibria, using a suitable refinement concept. In any equilibrium, the first agent offers the whole cake to the second proposal-maker, who in turn offers the whole cake back to the first agent. The third agent is then indifferent about dividing the cake between himself and the first or the second agent.division of a cake, majority decisions, tie-breaking rules