  Mean-field models of glasses that present a random first order transition
exhibit highly non-trivial fluctuations. Building on previous studies that
focused on the critical scaling regime, we here obtain a fully quantitative
framework for all equilibrium conditions. By means of the replica method we
evaluate Gaussian fluctuations of the overlaps around the thermodynamic limit,
decomposing them in thermal fluctuations inside each state and heterogeneous
fluctuations between different states. We first test and compare our analytical
results with numerical simulation results for the p-spin spherical model and
the random orthogonal model, and then analyze the random Lorentz gas. In all
cases, a strong quantitative agreement is obtained. Our analysis thus provides
a robust scheme for identifying the key finite-size (or finite-dimensional)
corrections to the mean-field treatment of these paradigmatic glass models.
