A computer is classically formalised as a universal Turing machine or a similar device. However over the years a lot of research has focused on the computational properties of dynamical systems other than Turing machines, such cellular automata, artificial neural networks, mirrors systems, etc.In this paper we propose a unifying formalism derived from a generalisation of Turing’s arguments. Then we review some of universal systems proposed in the literature and show that are particular case of this formalism. Finally, we review some of the attempts to understand the relation between dynamical and computational properties of a system. 相似文献
We obtain exact estimates in the arithmetical and analytical hierarchies of index sets of various classes of automatic models. We also obtain estimates for the existence problems for computable isomorphism and embedding of automatic structures. 相似文献
We present a stochastic critical slope sandpile model, where the amount of grains that fall in an overturning event is stochastic variable. The model is local, conservative, and Abelian. We apply the moment analysis to evaluate critical exponents and finite size scaling method to consistently test the obtained results. Numerical results show that this model, Oslo model, and one-dimensional Abelian Manna model have the same critical behavior although the three models have different stochastic toppling rules, which provides evidences suggesting that Abelian sandpile models with different stochastic toppling rules are in the same universality class. 相似文献
Athermal chains of various stiffness embedded in several types of lattices were analyzed with respect to their pair distribution function G(R). Extrapolation to infinite chain‐length on a reduced distance scale made all the G(R) data coincide within extremely narrow limits, thus suggesting the existence of a universal pair distribution function for polymers in good solvents in the long‐chain limit. The ratio –ln(G(R))/Z(R) with Z(R) being the reduced distribution of overlaps is also universal in type and varies only little with distance R. Further, a likewise universal function could be established that allows the construction of Z(R) from the Flory–Krigbaum expression taking into account not only the deviations from Gaussian behavior but also the effect of intramolecular repulsion present in athermal chains.
We study two-dimensional Coulomb systems confined in a disk with ideal dielectric boundaries. In particular we consider the two-component plasma in detail. When the coulombic coupling constant =2 the model is exactly solvable. We compute the grand potential, densities and correlations. We show that the grand potential has a universal logarithmic finite-size correction as predicted in previous works. This logarithmic finite-size correction is also found in the free energy of another solvable model: the one-component plasma. 相似文献
This paper is a review of the work done on the dynamics of modulated logistic systems. Three different problems are treated,
viz, the modulated logistic map, the parametrically perturbed logistic map and the combination map obtained by combining two
maps of the quadratic family. Many of the interesting features displayed by these systems are discussed. 相似文献
The electrical resistance of the binary liquid system cyclohexane + acetic anhydride is measured, in the critical region,
both in the pure mixture and when the mixture is doped with small amounts (≈ 100 ppm) of H2O/D2O impurities.Tc was approached to aboutt=3×10−6 wheret=(T −Tc)/Tc. The critical exponentb ≈ 0.35 in the fit of the resistance data to the equationdR/dT ∼t−b does not seem to be affected appreciably by the impurities. There is a sign reversal ofdR/dt in the non-critical region. Binary liquid systems seem to violate the universality of the critical resistivity. 相似文献
Ifμ-e universality is assumed, there are 17 neutral-current parameters of current experimental interest, including the parity-violating
nuclear force sector. We deduce the general relations among these parameters implied by gauge models. In single-Z boson models, there are 10 relations, while two-boson models lead to 4 relations. Ifμ-e universality is abandoned, the number of parameters increases to 31, while the number of relations becomes 21 in single-boson
models and 12 in two-boson models. We derive all these relations. 相似文献