A family of N-representability conditions are imposed on the third- and fourth-order reduced density matrix elements in order to ascertain that they are within bounds. These bounds are needed in the construction of high-order reduced density matrices as well as in the correction of the matrices which result from the iterative solution of the standard and of the modified contracted Schrodinger equations. The results obtained for the fourth-order reduced density matrix are strikingly good in two nontrivial cases. A new and more economical method for constructing the fourth-order reduced density matrix in terms of the lower order ones is also reported here. (C) 2001 John Wiley & Sons, Inc. [References: 28]
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机译：一族N可表示性条件被施加到三阶和四阶缩减密度矩阵元素上，以确定它们是否在范围之内。这些界限在构建高阶缩减密度矩阵以及校正由标准和修改后的压缩薛定inger方程迭代得出的矩阵时需要。在两个非平凡的情况下，四阶降密度矩阵获得的结果非常好。本文还报道了一种新的，更经济的方法来构造低阶矩阵的四阶降密度矩阵。 （C）2001 John Wiley＆Sons，Inc. [参考：28]
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