%0 Journal Article %T A unified fluctuation formula for one-cut $¦Â$-ensembles of random matrices %A Fabio Deelan Cunden %A Francesco Mezzadri %A Pierpaolo Vivo %J Mathematics %D 2015 %I arXiv %R 10.1088/1751-8113/48/31/315204 %X Using a Coulomb gas approach, we compute the generating function of the covariances of power traces for one-cut $\beta$-ensembles of random matrices in the limit of large matrix size. This formula depends only on the support of the spectral density, and is therefore universal for a large class of models. This allows us to derive a closed-form expression for the limiting covariances of an arbitrary one-cut $\beta$-ensemble. As particular cases of the main result we consider the classical $\beta$-Gaussian, $\beta$-Wishart and $\beta$-Jacobi ensembles, for which we derive previously available results as well as new ones within a unified simple framework. We also discuss the connections between the problem of trace fluctuations for the Gaussian Unitary Ensemble and the enumeration of planar maps. %U http://arxiv.org/abs/1504.03526v2