Multi-Structural Games and Number of Quantifiers
Multi-Structural Games and Number of Quantifiers
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多结构博弈和量词数量
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发表时间:
2021
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通讯作者:
Nikhil Vyas
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作者:
Ronald Fagin;J. Lenchner;Kenneth W. Regan;Nikhil Vyas
We study multi-structural games, played on two sets ${\mathcal{A}}$ and ${\mathcal{B}}$ of structures. These games generalize Ehrenfeucht-Fraïssé games. Whereas Ehrenfeucht-Fraïssé games capture the quantifier rank of a first-order sentence, multi-structural games capture the number of quantifiers, in the sense that Spoiler wins the r-round game if and only if there is a first-order sentence ϕ with at most r quantifiers, where every structure in ${\mathcal{A}}$ satisfies ϕ and no structure in ${\mathcal{B}}$ satisfies ϕ. We use these games to give a complete characterization of the number of quantifiers required to distinguish linear orders of different sizes, and develop machinery for analyzing structures beyond linear orders.