Extended quasi-additivity of Tsallis entropies

We consider statistically independent non-identical subsystems with different entropic indices q1 and q2. A relation between q1, q2 and q' (for the entire system) extends a power law for entropic index as a function of distance r. A few examples illustrate a role of the proposed constraint q' < min(q1, q2) for the Beck's concept of quasi-additivity.Comment: to appear in Physica

Modelling train delays with q-exponential functions

We demonstrate that the distribution of train delays on the British railway network is accurately described by q-exponential functions. We explain this by constructing an underlying superstatistical model.Comment: 12 pages, 5 figure

Generalized statistical mechanics of cosmic rays

We consider a generalized statistical mechanics model for the creation process of cosmic rays which takes into account local temperature fluctuations. This model yields Tsallis statistics for the cosmic ray spectrum. It predicts an entropic index q given by q=11/9 at largest energies (equivalent to a spectral index of alpha=5/2), and an effective temperature given by (5/9)T_H, where kT_H approximately equal to 180 MeV is the Hagedorn temperature measured in collider experiments. Our theoretically obtained formula is in very good agreement with the experimentally measured energy spectrum of primary cosmic rays.Comment: 10 pages, 2 figure

Generalized statistical mechanics and fully developed turbulence

The statistical properties of fully developed hydrodynamic turbulence can be successfully described using methods from nonextensive statistical mechanics. The predicted probability densities and scaling exponents precisely coincide with what is measured in various turbulence experiments. As a dynamical basis for nonextensive behaviour we consider nonlinear Langevin equations with fluctuating friction forces, where Tsallis statistics can be rigorously proved.Comment: 10 pages, 4 figures. To appear in Physica A (Proceedings of Statphys 21

Multifractal analysis of nonhyperbolic coupled map lattices: Application to genomic sequences

Symbolic sequences generated by coupled map lattices (CMLs) can be used to model the chaotic-like structure of genomic sequences. In this study it is shown that diffusively coupled Chebyshev maps of order 4 (corresponding to a shift of 4 symbols) very closely reproduce the multifractal spectrum $D_q$ of human genomic sequences for coupling constant $\alpha =0.35\pm 0.01$ if $q>0$. The presence of rare configurations causes deviations for $q<0$, which disappear if the rare event statistics of the CML is modified. Such rare configurations are known to play specific functional roles in genomic sequences serving as promoters or regulatory elements.Comment: 7 pages, 6 picture

Axiomatic approach to the cosmological constant

A theory of the cosmological constant Lambda is currently out of reach. Still, one can start from a set of axioms that describe the most desirable properties a cosmological constant should have. This can be seen in certain analogy to the Khinchin axioms in information theory, which fix the most desirable properties an information measure should have and that ultimately lead to the Shannon entropy as the fundamental information measure on which statistical mechanics is based. Here we formulate a set of axioms for the cosmological constant in close analogy to the Khinchin axioms, formally replacing the dependency of the information measure on probabilities of events by a dependency of the cosmological constant on the fundamental constants of nature. Evaluating this set of axioms one finally arrives at a formula for the cosmological constant that is given by Lambda = (G^2/hbar^4) (m_e/alpha_el)^6, where G is the gravitational constant, m_e is the electron mass, and alpha_el is the low energy limit of the fine structure constant. This formula is in perfect agreement with current WMAP data. Our approach gives physical meaning to the Eddington-Dirac large number hypothesis and suggests that the observed value of the cosmological constant is not at all unnatural.Comment: 7 pages, no figures. Some further references adde

Superstatistics

We consider nonequilibrium systems with complex dynamics in stationary states with large fluctuations of intensive quantities (e.g. the temperature, chemical potential, or energy dissipation) on long time scales. Depending on the statistical properties of the fluctuations, we obtain different effective statistical mechanics descriptions. Tsallis statistics is one, but other classes of generalized statistics are obtained as well. We show that for small variance of the fluctuations all these different statistics behave in a universal way.Comment: 12 pages /a few more references and comments added in revised versio

Stretched exponentials from superstatistics

Distributions exhibiting fat tails occur frequently in many different areas of science. A dynamical reason for fat tails can be a so-called superstatistics, where one has a superposition of local Gaussians whose variance fluctuates on a rather large spatio-temporal scale. After briefly reviewing this concept, we explore in more detail a class of superstatistics that hasn't been subject of many investigations so far, namely superstatistics for which a suitable power beta^eta of the local inverse temperature beta is chi^2-distributed. We show that eta >0 leads to power law distributions, while eta <0 leads to stretched exponentials. The special case eta=1 corresponds to Tsallis statistics and the special case eta=-1 to exponential statistics of the square root of energy. Possible applications for granular media and hydrodynamic turbulence are discussed.Comment: 10 pages. Proceedings of NEXT-SigmaPhi conference, Kolymbari, 13-18 August 200

Chaotic quantization and the mass spectrum of fermions

In order to understand the parameters of the standard model of electroweak and strong interactions, one needs to embed the standard model into some larger theory that accounts for the observed values. This means some additional sector is needed that fixes and stabilizes the values of the fundamental constants of nature. We describe how such a sector can be constructed using the so-called chaotic quantization method applied to a system of coupled map lattices. We restrict ourselves in this short note on verifying how our model correctly yields the numerical values of Yukawa and gravitational coupling constants of a collection of heavy and light fermions using a simple principle, the local minimization of vacuum energy.Comment: 8 pages, 6 figures. To appear in Chaos, Solitons and Fractals (2008

The R R --matrix action of untwisted affine quantum groups at roots of 1

Let $\hat{\frak g}$ be an untwisted affine Kac-Moody algebra. The quantum group $U_h(\hat{\frak g})$ (over $\mathbb{C}[[h]]$) is known to be a quasitriangular Hopf algebra: in particular, it has a universal $R$--matrix, which yields an $R$--matrix for each pair of representations of $U_h(\hat{\frak g})$. On the other hand, the quantum group $U_q(\hat{\frak g})$ (over $\mathbb{C}(q)$) also has an $R$--matrix for each pair of representations, but it has not a universal $R$--matrix so that one cannot say that it is quasitriangular. Following Reshetikin, one introduces the (weaker) notion of braided Hopf algebra: then $U_q(\hat{\frak g})$ is a braided Hopf algebra. In this work we prove that also the unrestricted specializations of $U_q(\hat{\frak g})$ at roots of 1 are braided: in particular, specializing $q$ at 1 we have that the function algebra $F \big[ \hat{H} \big]$ of the Poisson proalgebraic group $\hat{H}$ dual of $\hat{G}$ (a Kac-Moody group with Lie algebra $\hat{\frak g} \,$) is braided. This is useful because, despite these specialized quantum groups are not quasitriangular, the braiding is enough for applications, mainly for producing knot invariants. As an example, the action of the $R$--matrix on (tensor products of) Verma modules can be specialized at odd roots of 1.Comment: 12 pages, AMS-TeX C, Version 2.1c - this is the author's file of the final version (after the refereeing process), as sent for publicatio