%0 Journal Article %T The variance of the shock in the HAD process %A Cristian F. Coletti %A Pablo A. Ferrari %A Leandro P. R. Pimentel %J Mathematics %D 2008 %I arXiv %X We consider the Hammersley-Aldous-Diaconis (HAD) process with sinks and sources such that there is a microscopic shock at every time $t$; denote $Z(t)$ its position. We show that the mean and variance of $Z(t)$ are linear functions of $t$ and compute explicitely the respective constants in function of the left and right densities. Furthermore, we describe the dependence of $Z(t)$ on the initial configuration in the scale $\sqrt t$ and, as a corollary, prove a central limit theorem. %U http://arxiv.org/abs/0801.2526v1