Minimal S-universality criterion sets

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Minimal S-universality criterion sets

수리과학부 0 2726
구분 박사학위 논문 심사
일정 2019-11-18(월) 17:00~18:00
세미나실 129동 104호
강연자 이정원 (서울대학교)
담당교수 오병권
기타
For any set $S$ of positive definite and integral quadratic forms with bounded rank, there is a finite subset $S_{0}$ of S such that any $S_{0}$-universal quadratic form is also $S$-universal. Such a set $S_{0}$ is called an $S$-universality criterion set. In this talk, we introduce various properties on minimal $S$-universality criterion sets. When $S$ is a subset of positive integers, we show that the minimal $S$-universality criterion set is unique. For higher rank cases, we prove that a minimal $S$-universality criterion set is not unique when $S$ is the set of all qudratic forms of rank $n$ with $n ≥ 9$. We say a ℤ-lattice $L$ is recoverable if there is a minimal $S_{L}$-universality criterion set other than ${L}$, where $S_{L}$ is the set of all sublattices of $L$ with same rank. We provide some necessary conditions, and some sufficient conditions for ℤ-lattices to be recoverable.

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