Thomas Oikonomou

The maximization of Tsallis entropy with complete deformed functions and the problem of constraints

Abstract By only requiring the q deformed logarithms (q exponentials) to possess arguments chosen from the entire set of positive real numbers (all real numbers), we show that the q-logarithm (q exponential) can be written in such a way that its argument varies between 0 and 1 (among negative real numbers) for 1 ⩽ q 2 , while the interval 0 q ⩽ 1 corresponds to any real argument greater than 1 (positive real numbers). These two distinct intervals of the nonextensivity index q, also the expressions of the deformed functions associated with them, are related to one another through the relation ( 2 − q ) , which is so far used to obtain the ordinary stationary distributions from the corresponding escort distributions, and vice versa in an almost ad hoc manner. This shows that the escort distributions are only a means of extending the interval of validity of the deformed functions to the one of ordinary, undeformed ones. Moreover, we show that, since the Tsallis entropy is written in terms of the q-logarithm and its argument, being the inverse of microstate probabilities, takes values equal to or greater than 1, the resulting stationary solution is uniquely described by the one obtained from the ordinary constraint. Finally, we observe that even the escort stationary distributions can be obtained through the use of the ordinary averaging procedure if the argument of the q-exponential lies in ( − ∞ , 0 ] . However, this case corresponds to, although related, a different entropy expression than the Tsallis entropy.

A note on the definition of deformed exponential and logarithm functions

The recent generalizations of the Boltzmann–Gibbs statistics mathematically rely on the deformed logarithmic and exponential functions defined through some deformation parameters. In the present work, we investigate whether a deformed logarithmic/exponential map is a bijection from R+/R (set of positive real numbers/all real numbers) to R/R+, as their undeformed counterparts. We show that their inverse map exists only in some subsets of the aforementioned (co)domains. Furthermore, we present conditions which a generalized deformed function has to satisfy, so that the most important properties of the ordinary functions are preserved. The fulfillment of these conditions permits us to determine the validity interval of the deformation parameters. We finally apply our analysis to Tsallis q-deformed functions and discuss the interval of concavity of the Renyi entropy.

Properties of the “non-extensive Gaussian” entropy

The present work investigates the Lesche stability (experimental robustness), the thermodynamic stability, the Legendre structure of thermodynamics, and derives the maximum entropy distribution of the one-parametric “non-extensive Gaussian” entropy. We show that this entropy definition fulfills both stability conditions for all values of its parameter (q∈R). The entropy maximizer contains the Lambert W-function, which allows the preservation of the Legendre transformations.

Generalized entropic structures and non-generality of Jaynes’ Formalism

Abstract The extremization of an appropriate entropic functional may yield to the probability distribution functions maximizing the respective entropic structure. This procedure is known in Statistical Mechanics and Information Theory as Jaynes’ Formalism and has been up to now a standard methodology for deriving the aforementioned distributions. However, the results of this formalism do not always coincide with the ones obtained following different approaches. In this study we analyse these inconsistencies in detail and demonstrate that Jaynes’ formalism leads to correct results only for specific entropy definitions.

Phase Transition in

Surface plasmon polaritons (SPPs) are coherent electromagnetic surface waves trapped on an insulator-conductor interface. The SPPs decay exponentially along the propagation due to conductor losses, restricting the SPPs propagation length to few microns. Gain materials can be used to counterbalance the aforementioned losses. We provide an exact expression for the gain, in terms of the optical properties of the interface, for which the losses are eliminated. In addition, we show that systems characterized by lossless SPP propagation are related to PT symmetric systems. Furthermore, we derive an analytical critical value of the gain describing a phase transition between lossless and prohibited SPPs propagation. The regime of the aforementioned propagation can be directed by the optical properties of the system under scrutiny. Finally, we perform COMSOL simulations verifying the theoretical findings.

\mathcal {PT}

The existence and exact form of the continuum expression of the discrete nonlogarithmic q-entropy is an important open problem in generalized thermostatistics, since its possible lack implies that nonlogarithmic q-entropy is irrelevant for the continuous classical systems. In this work, we show how the discrete nonlogarithmic q-entropy in fact converges in the continuous limit and the negative of the q-entropy with continuous variables is demonstrated to lead to the (Csiszár type) q-relative entropy just as the relation between the continuous Boltzmann-Gibbs expression and the Kullback-Leibler relative entropy. As a result, we conclude that there is no obstacle for the applicability of the q-entropy to the continuous classical physical systems.

Symmetric Active Plasmonic Systems

Plastino and Curado [A. Plastino, E.M.F. Curado, Phys. Rev. E 72 (2005) 047103] recently determined the equilibrium probability distribution for the canonical ensemble using only phenomenological thermodynamical laws as an alternative to the entropy maximization procedure of Jaynes. In the current paper we present another alternative derivation of the canonical equilibrium probability distribution, which is based on the definition of the Helmholtz free energy (and its being constant at the equilibrium) and the assumption of the uniqueness of the equilibrium probability distribution. Noting that this particular derivation is applicable for all trace-form entropies, we also apply it to the Tsallis entropy, showing that the Tsallis entropy yields genuine inverse power laws.

Route from discreteness to the continuum for the Tsallis q -entropy

We recently provided a criterion of completeness valid for any generalized thermostatistics to check whether they form a bijection from ℝ + /ℝ (set of positive real numbers/all real numbers) to ℝ/ℝ + in a previous paper. In the current work, we apply this criterion to Kaniadakis, Abe and two-parameter generalized functions and obtain their respective validity ranges.

Canonical equilibrium distribution derived from Helmholtz potential

It has been known for some time that the usual q-entropy S_{q}^{(n)} cannot be shown to converge to the continuous case. In Phys. Rev. E 97, 012104 (2018)PREHBM2470-004510.1103/PhysRevE.97.012104, we have shown that the discrete q-entropy S[over ̃]_{q}^{(n)} converges to the continuous case when the total number of states are properly taken into account in terms of a convergence factor. Ou and Abe [previous Comment, Phys. Rev. E 97, 066101 (2018)10.1103/PhysRevE.97.066101] noted that this form of the discrete q-entropy does not conform to the Shannon-Khinchin expandability axiom. As a reply, we note that the fulfillment or not of the expandability property by the discrete q-entropy strongly depends on the origin of the convergence factor, presenting an example in which S[over ̃]_{q}^{(n)} is expandable.

A completeness criterion for Kaniadakis, Abe and two-parameter generalized statistical theories

Curado \textit{et al.} [Ann. Phys. \textbf{366} (2016) 22] have recently studied the axiomatic structure and the universality of a three-parameter trace-form entropy inspired by the group-theoretical structure. In this work, we study the group-theoretical entropy