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Computing Number Fluctuations

Girish S. Setlur·Yia-Chung Chang
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Abstract

Here we try and delienate the properties of the function that corresponds to fluctuations in the momentum distribution. The quantity denoted by $ N(k,k^{'}) $ is quite an interesting object. It satisfies various elegant sum rules and is also quite singular in some respects. All these properties are brought out and a formal connection is found between this object and the momentum distribution of the interacting and non-interacting many-fermion systems. This exercise is quite general in that it does not refer to any particular hamiltonian. It is also quite useful since in an earlier preprint(cond-mat/9810043) we showed how to compute the spectral function and single-particle lifetime of homogeneous Fermi systems where the only undetermined quantity was this function $ N(k,k^{'}) $.

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Girish S. Setlur, Yia-Chung Chang. 1998-10-23. Computing Number Fluctuations. https://arxiv.org/abs/cond-mat/9810308

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