Abstract

In this paper we study the determinacy strength of infinite games in the Cantor space and compare them with their counterparts in the Baire space. We show the following theorems:1. RCA0 ⊢ equation image-Det* ↔ equation image-Det* ↔ WKL0.2. RCA0 ⊢ 2-Det* ↔ ACA0.3. RCA0 ⊢ equation image-Det* ↔ equation image-Det* ↔ equation image-Det ↔ equation image-Det ↔ ATR0.4. For 1 < k < ω, RCA0 ⊢ k-Det* ↔ k –1-Det.5. RCA0 ⊢ equation image-Det* ↔ equation image-Det.Here, Det* stands for the determinacy of infinite games in the Cantor space, and k is the collection of formulas built from equation image formulas by applying the difference operator k – 1 times.