Schwinger probes

D. A. Mazziotti, Approximate solution for electron correlation through the use of Schwinger probes. Chem. Phys. Lett. 289, 419 (1998). 

The general relation between the differentiation of G J) with respect to the Schwinger probes and the ROMs may be characterized as... 

The coefficients of the multivariable Taylor series expansion of G J) about the point where the Schwinger probes vanish are elements of the ROMs. Thus G J) is known as the generating functional for ROMs. Mathematically, the RDMs of the functional G J) are known as the moments. The moment-generating functional G(y) may be used to define another functional W J), known as the cumulant-generating functional, by the relation... 

The Jk are the probe variables in this formulation (which Mazziotti [33] terms Schwinger probes )- We mention also Kutzelnigg and Mukherjee s treatment of RDMCs [28], which utihzes an antisymmetrized logarithm function, along with some special creation and annihilation operators, to generate the elements... 

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