Percolation and cosmic ray physics above $10^{17}$eV

Abstract

We argue that the energy dependence of the average position of the shower maximum, ${\bar{X}}_{max}$, and of the number of produced muons, $N_{\mu }$, can be explained by a change, around $10^{17}$eV, in the energy dependence of the inelasticity $K$, which decreases with the energy above the string percolation threshold.

Comments: 8 pages, 4 figures (6 eps files), latex