Regularity of the time constant for a supercritical Bernoulli percolation

We consider an i.i.d. supercritical bond percolation on Z^d , every edge is open with a probability p > p_c (d), where p_c (d) denotes the critical parameter for this percolation. We know that there exists almost surely a unique infinite open cluster C_p [11]. We are interested in the regularity properties of the chemical distance for supercritical Bernoulli percolation. The chemical distance between two points x, y $\in$ C_p corresponds to the length of the shortest path in C_p joining the two points. The chemical distance between 0 and nx grows asymptotically like n$\mu$_p (x). We aim to study the regularity properties of the map p $\to$ $\mu$_p in the supercritical regime. This may be seen as a special case of first passage percolation where the distribution of the passage time is G_p = p$\delta$_1 + (1 – p)$\delta$_$\mathrm{\infty }$ , p > p c (d). It is already known that the map p $\to$ $\mu$_p is continuous (see [10]).