In descriptive set theory, a set S {\displaystyle S} is said to be homogeneously Suslin if it is the projection of a homogeneous tree. S {\displaystyle S} is said to be κ {\displaystyle \kappa } -homogeneously Suslin if it is the projection of a κ {\displaystyle \kappa } -homogeneous tree. If A ⊆
ω ω {\displaystyle A\subseteq {}^{\omega }\omega } is a Π 1 1 {\displaystyle \mathbf {\Pi } _{1}^{1}} set and κ {\displaystyle \kappa } is a measurable cardinal, then A {\displaystyle A} is κ {\displaystyle \kappa } -homogeneously Suslin. This result is important in the proof that the existence of a measurable cardinal implies that Π 1 1 {\displaystyle \mathbf {\Pi } _{1}^{1}} sets are determined.
See also Projective determinacy
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