Abstract
Wishart random matrices with a sparse or diluted structure are ubiquitous in
the processing of large datasets, with applications in physics, biology and
economy. In this work we develop a theory for the eigenvalue fluctuations of
diluted Wishart random matrices, based on the replica approach of disordered
systems. We derive an analytical expression for the cumulant generating
function of the number of eigenvalues \$I\_N(x)\$ smaller than
\$xınR^+\$, from which all cumulants of \$I\_N(x)\$ and the
rate function \$\Psi\_x(k)\$ controlling its large deviation probability
\$ProbI\_N(x)=kN e^-N\Psi\_x(k)\$ follow. Explicit
results for the mean value and the variance of \$I\_N(x)\$, its rate
function, and its third cumulant are discussed and thoroughly compared to
numerical diagonalization, showing a very good agreement. The present work
establishes the theoretical framework put forward in a recent letter Phys.
Rev. Lett. 117, 104101 as an exact and compelling approach to deal with
eigenvalue fluctuations of sparse random matrices.
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