Rapisarda, Andrea; Stefan Thurner and Constantino Tsallis (Guest Editors)

An entropic functional S is said additive if it satisfies, for any two probabilistically independent systems A and B, that S(A+B)=S(A)+S(B). If not, it is said nonadditive. In the literature, since the pioneering works of Boltzmann (1872, 1877) [1,2], Gibbs (1902, 1948) [3,4], von Neumann (1927) [5], and Shannon (1948, 1949) [6,7], dozens and dozens of entropic functionals have been defined along the years. Only two of them are additive, namely the Boltzmann–Gibbs–von Neumann–Shannon one (hereafter referred to as SBG, where BG stands for Boltzmann–Gibbs), and the Rényi one SRq (1961, 1970) [8,9]. All others are generically nonadditive…