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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク 15 and 290 theorems ： ウィキペディア英語版 15 and 290 theorems The 15 theorem or Conway–Schneeberger Fifteen Theorem, proved by John H. Conway and W. A. Schneeberger in 1993, states that if a positive definite quadratic form with integer matrix represents all positive integers up to 15, then it represents all positive integers. The proof was complicated, and was never published. Manjul Bhargava found a much simpler proof which was published in 2000. In 2005, Manjul Bhargava and Jonathan P. Hanke announced a proof of Conway's conjecture that a similar theorem holds for integral quadratic forms, with the constant 15 replaced by 290. The proof is to appear in ''Inventiones Mathematicae''.〔Bhargava, M., & Hanke, J., (Universal quadratic forms and the 290-theorem ). ''Invent. Math.'', to appear.〕 == Details == In simple terms, the results are as follows. Suppose $Q\_$ is a symmetric square matrix with real entries. For any vector $x$ with integer components, define :$Q(x)\; =\; \backslash sum\_\; Q\_\; x\_i\; x\_j$ This function is called a quadratic form. We say $Q$ is positive definite if $Q(x)\; >\; 0$ whenever $x\; \backslash ne\; 0$. If $Q(x)$ is always an integer, we call the function $Q$ an integral quadratic form. We get an integral quadratic form whenever the matrix entries $Q\_$ are integers; then $Q$ is said to have integer matrix. However, $Q$ will still be an integral quadratic form if the off-diagonal entries $Q\_$ are integers divided by 2, while the diagonal entries are integers. For example, ''x''2 + ''xy'' + ''y''2 is integral but does not have integral matrix. A positive integral quadratic form taking all positive integers as values is called universal. The 15 theorem says that a quadratic form with integer matrix is universal if it takes the numbers from 1 to 15 as values. A more precise version says that, if a positive definite quadratic form with integral matrix takes the values 1, 2, 3, 5, 6, 7, 10, 14, 15 , then it takes all positive integers as values. Moreover, for each of these 9 numbers, there is such a quadratic form taking all other 8 positive integers except for this number as values. For example, the quadratic form :$w^2\; +\; x^2\; +\; y^2\; +\; z^2\backslash$ is universal, because every positive integer can be written as a sum of 4 squares, by Lagrange's four-square theorem. By the 15 theorem, to verify this, it is sufficient to check that every positive integer up to 15 is a sum of 4 squares. (This does not give an alternative proof of Lagrange's theorem, because Lagrange's theorem is used in the proof of the 15 theorem.) On the other hand, :$w^2\; +\; 2x^2\; +\; 5y^2\; +\; 5z^2,\backslash$ is a positive definite quadratic form with integral matrix that takes as values all positive integers other than 15. The 290 theorem says a positive definite integral quadratic form is universal if it takes the numbers from 1 to 290 as values. A more precise version states that, if an integer valued integral quadratic form represents all the numbers 1, 2, 3, 5, 6, 7, 10, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 34, 35, 37, 42, 58, 93, 110, 145, 203, 290 , then it represents all positive integers, and for each of these 29 numbers, there is such a quadratic form representing all other 28 positive integers with the exception of this one number. Bhargava has found analogous criteria for a quadratic form with integral matrix to represent all primes (the set ) and for such a quadratic form to represent all positive odd integers (the set ). Expository accounts of these result have been written by Hahn〔Alexander J. Hahn, (Quadratic Forms over $\backslash mathbb$ from Diophantus to the 290 Theorem ), Advances in Applied Clifford Algebras, 2008, Volume 18, Issue 3-4, 665-676〕 and Moon〔Yong Suk Moon, (Universal quadratic forms and the 15-theorem and 290-theorem )〕 (who provides proofs). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「15 and 290 theorems」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.