The ordinal Ramsey bound conjecture for well-founded trees

A well-founded tree is a prefix-closed set of finite sequences, and its order type is the ordinal order type used in the paper. A coloring of such a tree assigns each node one of two colors, red or black. Ordinal Ramsey bound conjecture. There is a reasonably simple ordinal-valued binary partial function FF such that, for all ordinals β\beta and γ\gamma, some ordinal αF(β,γ)\alpha\leq F(\beta,\gamma) has the property that every red-and-black coloring of every well-founded tree T0T_0 of order type α\alpha contains either a well-founded tree T1T_1 of order type β\beta homeomorphically embedded into the red nodes of T0T_0, or a well-founded tree T2T_2 of order type γ\gamma homeomorphically embedded into the black nodes of T0T_0. This is posed to generalize the finite-order-type Ramsey bounds established earlier in the appendix; no resolution is given.

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Primary source

Yohji Akama, “A new order theory of set systems and better quasi-orderings”, arXiv:1112.2801 (2012).

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